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Reward substitution: how consumers can be incentivized to choose smaller food portions

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Content Running head: REWARD SUBSTITUTION i!

Reward Substitution:
How Consumers Can Be Incentivized to Choose Smaller Food Portions

by

Martin Reimann

A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(PSYCHOLOGY)

May 2013

Copyright 2013 Martin Reimann
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ii!
Acknowledgements

I thank my primary advisor and dissertation chair, Antoine Bechara, for the great
opportunity to conduct research with him as well as for his continued inspiration and
constructive criticism during my five years as graduate student at USC. I learned a lot
from him about preciseness and distinctiveness in functional neuroanatomy and the
neuroanatomical bases of diverse aspects of human decision making. I thank my co-
advisor, Debbie MacInnis, for kindly introducing me to the dynamics of domestic
marketing academia and to cognitive appraisal theories of emotion, including the
emotional state of hoping, the latter of which resulted in an on-going, collaborative
research project that intrigues me. I thank John Monterosso for our stimulating
discussions on neuroeconomics and his insightful advice on my dissertation research. I
am thankful to Mike Dawson for introducing me to the psychophysiology of emotion,
and to Wendy Wood for encouraging me to take a closer look at some of the moderating
processes of reward substitution and food choice.
I show much gratitude to Judy Zaichkowsky, who has become my unofficial
advisor, for teaching me how to conduct investigations in the domain of consumer
research, which has led to several publications over the last few years.
I also thank my intellectual sparring partner, Oliver Schilke, for his ongoing
support, insight, and scholarly challenge related to this and other research projects. I
would surely not have been able to achieve this work without him.
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iii!
I was also very fortunate to work with several brilliant post-baccalaureate
collaborators and motivated undergraduate research assistants throughout my graduate
studies. I thank Armin Heinecke for rigorously training and supporting me in brain
imaging data analysis, using the Brain Voyager software. I thank Ulysses Hsu and
Michael Huang for help with designing the online experiment, Stephanie Castillo, Jaclyn
Espinosa, Ben Howie, and Jiancheng Zhuang for their support with neuroimaging data
collection during countless hours at the Dornsife Neuroimaging Center, and Sebastian
Lehmann and Wilko Feye for preprocessing support.
I am indebted to the Google & WPP Marketing Research Program and the
University of Southern California for generous funding during my graduate studies. I
understand that such opportunities in life are not the norm but extraordinary exceptions
for which I am very grateful.
Last but certainly not least, I thank my parents Günter and Gabriele and my
brother Andreas for their continued believe in my academic goals and for supporting my
scholarly endeavors along the way.

Martin Reimann
Los Angeles, California, May 2013
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Signature Page

This dissertation, written by

Martin Reimann

under the direction of the dissertation committee and
approved by all its members, has been presented to
and accepted by the Graduate School in partial
fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Sarah Pratt
Vice Provost for Graduate Programs
Date

Dissertation Committee
Antoine Bechara, Chair
Michael E. Dawson
Deborah MacInnis
John Monterosso
Wendy Wood
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Table of Contents

List of Tables…………………………………………………………………………….vii
List of Figures…………………………………………………………………………….ix
Abstract…………………………………………………………………………………...xi

Chapter 1. Introduction……………………………………………………………………1

Chapter 2. Conceptual Background and Hypotheses…………………………….……….8
2.1. Determinants of Smaller Portion Choice………………………………….….9
2.2. Reward Substitution as an Additional Determinant of Smaller Portion
Choice……………………………………………………………………………14
2.3. Incentive Salience: A Common Process Underlying the Effect of Reward
Substitution on Smaller Portion Choice…………………………………………16
2.4. Alternative Process Mechanisms……………………………………………21

Chapter 3. Study 1: The Reward Substitution Effect……………………………………26
3.1. Introduction…………………………………………………………………26
3.2. Method……………………………………….……………………………..28
3.3. Results……………………………………….……………………………...35
3.4. Discussion……………………………………….…………..……………...69
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Chapter 4. Study 2: The Underlying Neurophysiological Mechanisms of the Reward
Substitution Effect……………………….……………………………………………..73
4.1. Introduction………………………………………………………………..73
4.2. Method……………………………………….……………………………74
4.3. Results……………………………………….…………………………….83
4.4. Discussion……………………………………….……………………….100

Chapter 5. General Discussion……………………….………………………………104
5.1. Introduction……………………………………………………………...104
5.2. Contributions..…………………………………………………………...107
5.3. Limitations and Implications for Future Research……….….…………..110
5.4. Practical Implementation and Public Policy Implications..……………...111

References……………………….……………………………………………………113
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List of Tables

Table 1: Age moderates the reward substitution effect……………………….…..40
Table 2: Gender does not moderate the reward substitution effect…………….…41
Table 3: BMI moderates the reward substitution effect…………………………..42
Table 4: Satiety does not moderate the reward substitution effect………………..43
Table 5: Importance of food being healthy moderates the reward substitution
effect…………………………………………………………………….44
Table 6: Importance of food being able to lead to good mood moderates the reward
substitution effect……………………………………………………….45
Table 7: Importance of food being convenient does not moderate the reward
substitution effect……………………………………………………….46
Table 8: Importance of food being sensorically appealing does not moderate the
reward substitution effect……………………………………………….47
Table 9: Importance of food being natural does not moderate the reward
substitution effect………………………………………………………48
Table 10: Importance of food being attainable at a low price moderates the reward
substitution effect……………………………………………………….49
Table 11: Importance of food being weight-controlling moderates the reward
substitution effect……………………………………………………….50
Table 12: Importance of food being familiar moderates the reward substitution
effect…………………………………………………………………….51
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Table 13: Importance of food being ethical does not moderate the reward
substitution effect………………………………………………………..52
Table 14: Positive affect moderates the reward substitution effect………………...54
Table 15: Negative affect moderates the reward substitution effect…………….….55
Table 16: Satisfaction with life moderates the reward substitution effect……….…56
Table 17: Overall impulsivity moderates the reward substitution effect……….…..58
Table 18: Attention moderates the reward substitution effect………………….…..59
Table 19: Motor impulsivity moderates the reward substitution effect………….…60
Table 20: Self-control moderates the reward substitution effect…………………...61
Table 21: Cognitive complexity moderates the reward substitution effect………...62
Table 22: Perseverance moderates the reward substitution effect………………….63
Table 23: Cognitive instability moderates the reward substitution effect………….64
Table 24: BIS moderates the reward substitution effect……………………….…...66
Table 25: BAS reward responsiveness does not moderate the reward substitution
effect……………………………………………………………………..67
Table 26: BAS drive moderates the reward substitution effect…………………….68
Table 27: BAS fun seeking does not moderate the reward substitution effect……..69
Table 28: Overlapping BOLD responses in first time interval……………………...69
Table 29: Overlapping BOLD responses in second time interval…………………..89
Table 30: Overlapping BOLD responses in third time interval…………………….91
Table 31: Meta-analytic results on the basis of the neurosynth.org database
(Yarkoni, Poldrack, Nichols, Van Essen, & Wager, 2011)……………...96
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List of Figures

Figure 1: Research questions of this thesis…………………………………………...3
Figure 2: Conceptual model of this research…………………………………………5
Figure 3: Thesis overview: Chapter 1………………………………………………...7
Figure 4: Thesis overview: Chapter 2………………………………………………...8
Figure 5: Recent work on determinants of smaller portion choice and classification
of the present research…………………………………………………...10
Figure 6: The dopaminergic link between the ventral tegmental area and the
striatum…………………………………………………………………..18
Figure 7: Thesis overview: Chapter 3……………………………………………….26
Figure 8: Full portion stimuli………………………………………………………..30
Figure 9: Half portion stimuli……………………………………………………….31
Figure 10: Exemplary task view on computer screen………………………………...33
Figure 11: Trial structure and timing of online experimental task……………………34
Figure 12: Study 1: Percentage of full portion choice decreases with increasing
lottery amount……………………………………………………………36
Figure 13: Study 1: Moderators of the reward substitution effect……………….…..39
Figure 14: Thesis overview: Chapter 4……………………………………………….74
Figure 15: Exemplary view of E-Prime task………………………………………….77
Figure 16: Trial structure and timing of experimental task in the fMRI study………..79
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Figure 17: Study 2: Percentage of full portion choice decreases with increasing
lottery amount……………………………………………………………85
Figure 18: Significant increase in BOLD response in the dorsal striatum compared to
baseline…………………………………………………………………..86
Figure 19: Significant increase in BOLD response in the dorsal striatum compared to
baseline…………………………………………………………………..87
Figure 20: Significantly overlapping BOLD responses in the dorsal striatum for the
four experimental conditions……………………………………………92
Figure 21: Significantly overlapping BOLD responses in the dorsal striatum for the
four experimental conditions…………………………………………….93
Figure 22: The dopaminergic link between the ventral tegmental area and the
prefrontal cortex……………………………………………………….101
Figure 23: Thesis overview: Chapter 5…………………………………………...…104

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Abstract

This research establishes that offering non-food rewards (i.e., lottery tickets) bundled with
smaller food portions as an alternative to full-portion meals can substantially decrease
chosen portion sizes. Study 1, a behavioral experiment and field survey, establishes this
effect, which I call “reward substitution,” among adult consumers from the general
population. The impact of possible boundary conditions and moderating variables on this
effect are investigated and reported. Study 2, a functional magnetic resonance imaging
(fMRI) experiment, finds that the reward substitution effect is based on a common
neurophysiological process that becomes evident in structures of the mesolimbic dopamine
system. The current research introduces reward substitution as another determinant of
smaller portion choice and has implications for portion size research, the psychology of
self-control, and classical theories of motivation and economic utility. Implications for
future research are provided, and suggestions for practical implementation and public
policy making are discussed.

Keywords: reward and positive reinforcement, incentive saliance, wanting, smaller food
portion choice, mesolimbic dopamine system, striatum, fMRI, neuromarketing, consumer
neuroscience
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Chapter 1. Introduction

In many societies around the globe, food has become abundant and calorie-rich. A
pandemic of overweight and obesity has resulted, with high costs to governments,
businesses, and individual consumers. The medical sciences’ remedy to this issue seems
deceptively simple: Consumers should eat less (Lamberg, 2006). However, this advice is
easier to give than to follow or enforce in societies that value having freedom and a variety
of available options. One stream of research shows that—without altering satiation—
smaller portion sizes can drastically decrease the overall quantity of food consumed (e.g.,
Geier, Rozin, & Doros, 2006; B. J. Rolls, Roe, & Meengs, 2006; Rozin, Kabnick, Pete,
Fischler, & Shields, 2003). Importantly, reduction in food portion size and energy density
lead to a significant decrease in energy intake (B. J. Rolls, et al., 2006). As such, eating less
seems not to go at the expense of being satisfied and satiated. As a matter of fact, we
typically eat more than we need to be satiated. Because portion sizes offered to us are often
huge (Prentice & Jebb, 2003), and because we are often “mindless” eaters without
investing much deliberate thought into what and how much we eat (Wansink, 2007), we
tend to over-consume food, which today frequently results in overweight or obesity.
Additionally, our ancestral past dictates the storage of energy reserves in food-abundant
times for later use during scarcity (Ulijaszek, 2002).
The aforementioned notion of decreasing food intake by altering portion sizes has
been further investigated in several different yet related variants such as smaller assortment
sizes (Kahn & Wansink, 2004; Redden & Hoch, 2009; B. J. Rolls et al., 1981), smaller
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package sizes (Scott, Nowlis, Mandel, & Morales, 2008; Wansink, 1996; Wansink & Kim,
2005; Wansink & Park, 2001), taller and more slender food containers (Wansink & Van
Ittersum, 2003), and smaller bowls and plates (Van Ittersum & Wansink, 2012; Wansink &
Cheney, 2005; Wansink, Van Ittersum, & Painter, 2006).
However, extant research has largely missed addressing the issue of how consumers
can be incentivized to choose such smaller portions—a highly relevant question in a world
of “family-sized” cereal cartons (Wansink & Van Ittersum, 2007), all-you-can-eat buffets
(Wansink & Payne, 2008), and restaurants where tempting “super-sized” meals are offered
ubiquitously (e.g., Hill & Peters, 1998; Nestle, 2003; Nielsen & Popkin, 2003).
Moreover, from a business perspective, recent marketing research has shown that
some profit-maximizing firms have dropped smaller portion sizes from their portfolios and
menus because of decreased demand (Sharpe, Staelin, & Huber, 2008) and that introducing
smaller food packages to the marketplace may only be profitable for firms under very
specific circumstances (Jain, 2012). This raises the question of whether firms should
actively offer such smaller packages and risk losing profitability.
In order to answer these important questions and fill this unforeseen gap in the
extant literature on food choice and consumption, the present research introduces a novel
food offering that promotes eating less, possibly without hurting food manufacturers’ and
restaurants’ profitability. This food offering entails half-sized meals paired with non-food
rewards, such as a lottery ticket, at the same price as a full-sized meal. Two novel studies
establish and validate a novel food choice effect, which I call “reward substitution” (or,
“partial reward substition” because the food stimulus is not entirely but partially replaced
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by the non-food stimulus). For the purpose of this research, I define
the exchange of parts of a food
on the classical definition of reinforcing stimuli from operant conditioning research, which
are typically described as stimuli that increase the likelihood of a preferred response by
being applied succeeding the preferred r
important to note that while all rewards (e.g., food, money, and play) represent reinforcers,
not all reinforcers are rewards. For example, while electric shocks have a reinforcing effect
by bolstering avoidance responses, they do not represent a reward
1976). As such, I follow the established definition of rewards being positive reinforcers,
which are sometimes also referred to as incentive stimuli
summarizes the research questions under investigation in this thesis.
RESEARCH QUESTIONS O

1
It is important to note that related
elasticity (e.g., Allison, 1983) and reinforcer sensi
While the former refers to the abso
(Allison, 1983) and while the latter refers to the notion that a reinforcer can potentiate the conditioned
reinforcement in the sense of increasing the sensitivity to the behavioral effects of the reinforcer
et al., 1998), my definition of reward substitution
another non-food reward.
REWARD SUBSTITUTION
For the purpose of this research, I define reward substitution
change of parts of a food reward with another non-food reward. This definition builds
on the classical definition of reinforcing stimuli from operant conditioning research, which
are typically described as stimuli that increase the likelihood of a preferred response by
being applied succeeding the preferred response (Reynolds, 1975; Skinner, 1938)
important to note that while all rewards (e.g., food, money, and play) represent reinforcers,
rs are rewards. For example, while electric shocks have a reinforcing effect
by bolstering avoidance responses, they do not represent a reward (Maier & Seligman,
llow the established definition of rewards being positive reinforcers,
which are sometimes also referred to as incentive stimuli (Schultz, 2000).
1
Figure 1
summarizes the research questions under investigation in this thesis.
FIGURE 1
RESEARCH QUESTIONS OF THIS THESIS

It is important to note that related labels for “reward substitution” exist in the literature, such as reinforcer
and reinforcer sensitivity (e.g., Glautier, Bankart, Rigney, & Willner, 1998)
the absolute value of the reinforcer demand curve’s slope at a specific price
and while the latter refers to the notion that a reinforcer can potentiate the conditioned
f increasing the sensitivity to the behavioral effects of the reinforcer
ward substitution strictly refers to exchange of parts of a food reward with
3
reward substitution as
reward. This definition builds
on the classical definition of reinforcing stimuli from operant conditioning research, which
are typically described as stimuli that increase the likelihood of a preferred response by
(Reynolds, 1975; Skinner, 1938). It is
important to note that while all rewards (e.g., food, money, and play) represent reinforcers,
rs are rewards. For example, while electric shocks have a reinforcing effect
(Maier & Seligman,
llow the established definition of rewards being positive reinforcers,
Figure 1
” exist in the literature, such as reinforcer
(e.g., Glautier, Bankart, Rigney, & Willner, 1998).
at a specific price
and while the latter refers to the notion that a reinforcer can potentiate the conditioned
f increasing the sensitivity to the behavioral effects of the reinforcer (Glautier,
exchange of parts of a food reward with
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4
In Study 1 of the present research, I present initial evidence for the reward
substitution effect in a population of adult consumers. Further, I analyze whether this
behavioral effect remains significant when considering important boundaries such as levels
of satiety and body mass index. Additionally, the moderating impacts of several different
important variables are investigated, including demographics (i.e., age, gender), preference-
related variables (e.g., importance of food being convenient), emotional well-being, trait
impulsivity, and variables related to systems of behavioral inhibition and behavioral
activation.
Study 2 provides convergent behavioral evidence by showing replication of Study
1’s findings. More importantly, given that Study 2 was conducted while participants were
undergoing functional magnetic resonance imaging (fMRI), I investigate the underlying
neurophysiological processes associated with choosing the half-sized meal with the non-
food reinforcer compared to choosing regular full-sized meals without such non-food
reinforcers. Recent neuroimaging research has independently shown brain activation in the
same mesolimbic dopamine system—particularly, the striatum—for valuating distinct
rewards such as food (Berridge, 1996), money (Knutson, Adams, Fong, & Hommer, 2001),
beautiful faces (Aharon et al., 2001), and aesthetic packages (Reimann, Zaichkowsky,
Neuhaus, Bender, & Weber, 2010). My research builds on the idea of a common neural
currency (Montague & Berns, 2002; Schultz, Dayan, & Montague, 1997; Wise, 1978) to
see if the combination of a small food portion and a non-food reward would add up in
terms of striatal activation (or, indirectly, mesolimbic dopamine) to the striatal activation of
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a large food portion alone. Figure 2 illustrates the conceptual model under investigation in
the present research.
CONCEPTUAL MODEL OF
Taken together, the findings from the studies presented in this thesis represent a
comprehensive examination of the
and a neuroimaging experiment. This research
consumer food choice by showing that attempts
(1) is behaviorally effective; (2) is resistant against powerful boundaries such as high
hunger levels and higher body
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portion alone. Figure 2 illustrates the conceptual model under investigation in
FIGURE 2
CONCEPTUAL MODEL OF THIS THESIS
Taken together, the findings from the studies presented in this thesis represent a
of the reward substitution effect, both with behavioral studies
and a neuroimaging experiment. This research contributes to the extant literature on
consumer food choice by showing that attempts to promote choice of smaller food portions
(2) is resistant against powerful boundaries such as high
body mass indices; (3) is moderated by preference, emotional
5
portion alone. Figure 2 illustrates the conceptual model under investigation in

Taken together, the findings from the studies presented in this thesis represent a
effect, both with behavioral studies
to the extant literature on
choice of smaller food portions
(2) is resistant against powerful boundaries such as higher
emotional
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well-being, trait impulsivity, and behavioral inhibition/behavioral activation; and (4)
involves similar levels of dopaminergic reward.
Following this introductory Chapter 1, Chapter 2 reviews the extant literature on the
determinants of smaller portion choice. The domain of consumer psychology has a rich
history of investigations into the drivers of food choice, which provide important clues for
the present work and is therefore extensively reviewed (Chapter 2.1.). Subsequently,
reward substitution is introduced as an additional, novel driver of smaller portion choice
that may circumnavigate some of the issues with the drivers advanced by prior research
(Chapter 2.2.). Furthermore, because this research builds on the notion of a common
reward currency at the brain level (Montague & Berns, 2002; Schultz, et al., 1997; Wise,
1978), I investigate the concept of incentive salience, which I hypothesize represents the
underlying factor in the relationship between reward substitution and smaller portion
choice (Chapter 2.3). Hypotheses will be derived from the extant literature. Following
Chapter 2 on the conceptual background and hypotheses, I will report two empirical
studies: one carried out via a commercial web survey provider (Chapter 3) and another
conducted in the lab and used functional magnetic resonance imaging (fMRI) to tap into
the underlying mechanisms at the brain level (Chapter 4). Finally, Chapter 5 concludes the
thesis with an extensive general discussion that highlights important contributions and
research implications for research on portion size, the psychology of self-control, and
motivational theories. Implications for practitioners and public policy makers are discussed
as well as whether restaurants and food manufacturers should actively offer smaller portion
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sizes, despite decreased consumer demand and the risk of losing profita
provides an overview of the thesis structure.
THESIS OVERVIEW

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sizes, despite decreased consumer demand and the risk of losing profitability. Figure 3
thesis structure.
FIGURE 3
THESIS OVERVIEW: CHAPTER 1

7
Figure 3

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Chapter 2.

This chapter (Figure 4)
substitution, and highlights the core neurophysiological process that
substitution: smaller portion choice link.
determinants of food choice. Then, Section
of reward substitution in food choice.
incentive salience—embedded in theories of reward motivation and common currency
mechanism responsible for the
THESIS OVERVIEW:
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2. Conceptual Background and Hypotheses
) examines the previous literature, introduces reward
the core neurophysiological process that may underlie
smaller portion choice link. First, Section 2.1 presents an in-depth review of the
Then, Section 2.2 hypothesizes on the behavioral effectiveness
in food choice. Finally, Section 2.3 hypothesizes that the concept of
embedded in theories of reward motivation and common currency
mechanism responsible for the reward substitution effect.
FIGURE 4
THESIS OVERVIEW: CHAPTER 2
8
reward
underlie reward
depth review of the
on the behavioral effectiveness
that the concept of
embedded in theories of reward motivation and common currency—is a

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2.1. Determinants of Smaller Portion Choice

Food choice and food consumption has been a popular area of investigation in
consumer psychology for over three decades. Researchers have examined the effect of food
samples on obese and non-obese consumers (Steinberg & Yalch, 1978) , the effects of
nutrition information and health claims on food purchase behavior in both supermarkets
(Russo, Staelin, Nolan, Russell, & Metcalf, 1986) and restaurants (Chandon & Wansink,
2007; Howlett, Burton, Bates, & Huggins, 2009), and when healthy food makes consumers
hungry (Finkelstein & Fishbach, 2010) and can lead to choosing an indulgent alternative
(Wilcox, Vallen, Block, & Fitzsimons, 2009). So far, consumer psychologists have applied
a broad range of theoretical perspectives to food choice and consumption that includes
psychological drivers as well as social and stimulus-based contextual aspects (Block,
2012).
Notably, researchers have studied ways to entice consumers to choose smaller
portions, thus lowering food intake in an attempt to fight overweight and obesity. This
body of research provides an initial direction on how consumers may voluntarily substitute
bigger portions with smaller ones. Prior research has proposed several different
determinants of smaller portion choice, which are related to size perceptions and size
processing, social influence, and other environmental factors. Figure 5 illustrates the
determinants of smaller portion choice, which leads to smaller portion choice, and classifies
the present research as an additional driver of smaller portion choice.
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RECENT WORK ON DETER
CLASSIFICATION OF TH
Size Perception and Size Processing as Determinants
packages, containers, bowls, plates, and portions have been identified as determinants of
smaller portion choice. Specifically,
instead of three or uni-colored M&Ms instead of multicolored ones) have been shown to
decrease the food quantity consumed
J. Rolls, et al., 1981). Smaller packages
Wansink & Kim, 2005; Wansink & Park, 2001)
restrictions: Restrained eaters were found to consume more calories from small food in
small packages, while unrestrained eaters consumed more calories from large food in a
large package (Scott, et al., 2008)
as elongated glasses, were found to reduce the amount of juice poured
Ittersum, 2003). Similarly, consumers were found to serve themselves less food from
smaller bowls and plates than larger ones
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FIGURE 5
RECENT WORK ON DETERMINANTS OF SMALLER PORTION CHOICE AND
CLASSIFICATION OF THE PRESENT RESEARCH

Size Perception and Size Processing as Determinants. Smaller sizes of assortments,
packages, containers, bowls, plates, and portions have been identified as determinants of
smaller portion choice. Specifically, smaller assortment sizes (e.g., one yogurt brand
colored M&Ms instead of multicolored ones) have been shown to
decrease the food quantity consumed (Kahn & Wansink, 2004; Redden & Hoch, 2009; B.
maller packages also encourage less consumption (Wansink, 1996;
Wansink & Kim, 2005; Wansink & Park, 2001). Yet this effect may depend on dietary
restrictions: Restrained eaters were found to consume more calories from small food in
small packages, while unrestrained eaters consumed more calories from large food in a
(Scott, et al., 2008). Moreover, taller and more slender food containers
as elongated glasses, were found to reduce the amount of juice poured (Wansink & Va
. Similarly, consumers were found to serve themselves less food from
than larger ones (Van Ittersum & Wansink, 2012; Wansink &
10
ORTION CHOICE AND
maller sizes of assortments,
packages, containers, bowls, plates, and portions have been identified as determinants of
(e.g., one yogurt brand
colored M&Ms instead of multicolored ones) have been shown to
(Kahn & Wansink, 2004; Redden & Hoch, 2009; B.
(Wansink, 1996;
. Yet this effect may depend on dietary
restrictions: Restrained eaters were found to consume more calories from small food in
small packages, while unrestrained eaters consumed more calories from large food in a
food containers, such
(Wansink & Van
. Similarly, consumers were found to serve themselves less food from
(Van Ittersum & Wansink, 2012; Wansink &
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Cheney, 2005; Wansink, et al., 2006). Additionally, offering smaller portions is a major
determinant of smaller portion choice (Ello-Martin, Ledikwe, & Rolls, 2005; Geier, et al.,
2006; Kral & Rolls, 2004; B. J. Rolls, Morris, & Roe, 2002; B. J. Rolls, Roe, Kral, Meengs,
& Wall, 2004; B. J. Rolls, et al., 2006) and has been shown to be effective in several
different environments (restaurants: Diliberti, Bordi, Conklin, Roe, & Rolls, 2004) and
populations (children: Fisher, Liu, Birch, & Rolls, 2007; women: Kral, Roe, & Rolls, 2004;
French people: Rozin, et al., 2003).
Cognitive biases and perceptual illusions have been offered as explanations for
these different size-related effects. For example, the unit bias (i.e., a sense that a single
entity is the proper amount to consume) has been suggested as a rationale for the effect of
portion size perception on smaller portion choice. In particular, researchers show that
consumers chose much less snacks when offered a small as opposed to a large unit size
(Geier, et al., 2006). Furthermore, the plate size effect has recently been explained by the
Delboeuf illusion, in which one of two identical circles was perceived larger if surrounded
by a much larger circle, while the other one was surrounded by only a slightly larger circle.
Because of this illusion, consumers over-serve themselves on larger plates and under-serve
themselves on smaller ones (Van Ittersum & Wansink, 2012). Across these different
studies, the general rule emerges that smaller perceived and processed sizes generally lead
consumers to choose and consume smaller portions.
However, some interesting, counterintuitive evidence has been brought forward that
contradicts this general rule. Specifically, it was shown that when tempting foods came in
large packages, individuals consumed the least because of a self-control conflict (Do Vale,
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Pieters, & Zeelenberg, 2008). Researchers also found that consumers were more likely to
choose reduced fat ice cream from a larger than from a smaller assortment (Sela, Berger, &
Liu, 2009). A recent field study reported that consumers given a cookie plate marked as
“medium size” ate significantly more than those for whom the same plate was marked as
“large size” (Aydinoglu & Krishna, 2011). Another field study showed that diners
consumed more from smaller rather than larger forks, because diners had a well-defined
goal of hunger satiation (Mishra, Mishra, & Masters, 2012). In summary, although strong
convergent evidence for the “smaller-sizes-equals-less-intake” rule has been presented,
recent studies suggest that this rule may not be as straightforward as it seems.
Social Influence as Determinant. In addition to these size perception and size
processing effects, social influence has a profound impact on getting consumers to choose
smaller portions. Investigators reported that eating alone compared to eating in groups
leads consumers to choose less food (Berry, Beatty, & Klesges, 1985). More recently,
research showed that consumers chose less when choosing food in social isolation than
when they observe another consumer selecting a large portion (McFerran, Dahl,
Fitzsimons, & Morales, 2010). Similarly, a study found that being exposed to a person with
a neutral or healthy weight led consumers to take less candy compared to when exposed to
a overweight person (Campbell & Mohr, 2011). These findings on social influence being a
determinant of smaller portion choice may have some of their roots in identity- and status-
related processes. For example, presenting eating junk food as marker of an avoidance
group led consumers to choose less fattening food (Berger & Rand, 2008). Furthermore,
perceiving being fit as a signal of greater status led underprivileged consumers to prefer
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smaller snacks, yet this effect reversed when being overweight was perceived as a greater
status signal (Dubois, Rucker, & Galinsky, 2012).
Besides size perception and size processing as well as social influence, other
determinants of smaller portion choice have been suggested. These determinants include,
for example, increased behavioral effort, such as walking further to obtain a snack
compared to having the snack close by (Wansink, 2004); less ambiguous labeling, naming,
and serving size information, such as not labeling snacks as “low fat” or “healthy” (Irmak,
Vallen, & Robinson, 2011; Wansink & Chandon, 2006); as well as positive incidental
affect, such as happy mood states (Garg, Wansink, & Inman, 2007).
What has not been systematically shown so far is how consumers can be motivated
to choose smaller portions. This is an important question in today’s marketplace, where
restaurants have stopped offering smaller portion sizes because of decreased demand
(Sharpe, et al., 2008) or profitability issues (Jain, 2012), and many consumers are under the
social influence of others (e.g., Campbell & Mohr, 2011; McFerran, et al., 2010).
Legislation has not yet implemented many of marketing research’s public policy
implications such as taking the ambiguity out of food names and labels (e.g., Irmak, et al.,
2011; Wansink & Chandon, 2006). A recent review of 13 studies on the effect of size
perception on portion choice found that “value for money” (i.e., perceiving a lower unit
price) and “portion distortion” (i.e., perceiving larger portion sizes as appropriate amount)
are powerful mechanisms explaining why many consumers find larger portions more
attractive than smaller ones and thus choose larger meals despite smaller portion
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alternatives (Steenhuis & Vermeer, 2009). This begs the question of how one can possibly
override these potent mechanisms.
Heeding this gap in extant research, the present research investigates another
important determinant of smaller portion choice to determine if and how food and non-food
rewards can be substituted in order to provide a non-food incentive for consumers to
choose and consume less. I call this determinant “reward substitution,” defined as the
exchange of parts of a food reward with another non-food reward.

2.2. Reward Substitution as an Additional Determinant of Smaller Portion Choice

The goal of the present research is to investigate if the substitution of a food
reinforcer with another non-food reinforcer could explain the choice of a smaller food
portion. Some clues from behavioral research are coherent with my account of different
reinforcers being closely intertwined. Clinical work on substance abuse therapy has shown
that paying drug users with monetary vouchers for each negative drug test can help them
stay off drugs (Higgins et al., 1991; also see Lussier, Heil, Mongeon, Badger, & Higgins,
2006 for a meta-analysis). Investigators have shown that feeling hungry or feeling poor
have comparable effects on preferences for potential partners: Men who felt hungry or poor
preferred heavier women than men who felt full or rich. This finding was explained by a
social-cognitive account of experiencing resource scarcity for both food and money, which
is perhaps rooted in common affective and physiological states (Nelson & Morrison, 2005).
Following this notion, I expect that experiencing scarcity in one domain (food) may
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motivate consumers to seek resources in another domain (money). One group of
researchers found that hungry subjects were less likely to donate to charity than satiated
ones. The authors proposed an evolutionary account for the reciprocality of food and
money, suggesting that consumers’ desire for money is a modern derivative of the desire
for food (Briers, Pandelaere, Dewitte, & Warlop, 2006).
Building on the notion of behaviorally intertwined reinforcers, food and money can
be partially substituted for the sake of incentivizing consumers to choose smaller portions.
In addition to contributing to the stream of literature on the determinants of smaller portion
choice, this proposition has important theoretical implications for both motivational
psychology and the canonical economic model. First, contradicting traditional motivational
theories that assume a hierarchical structure of needs (Kenrick, Griskevicius, Neuberg, &
Schaller, 2010; Maslow, 1943), this theory supposes reward substitution across need
hierarchy levels—that is, substituting food with a reinforcer from a different need category
(e.g., desiring money) is effective even in situations in which consumers actively seek food
and are hungry. Second, challenging the canonical economic model that assumes that
money’s utility is indirect and that money is a simple counter and valued only for the goods
or services it can buy (a view that has been criticized recently, cf. Camerer, Loewenstein, &
Prelec, 2005), food and money command analogous reinforcement and are thus
substitutable. Because of such interchangeability across need hierarchies and comparable
reinforcement potency, I expect that substituting food with non-food reinforcers leads
consumers to choose smaller portions. Thus, it is hypothesized:

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H1: Substituting food reinforcers with non-food reinforcers determines
smaller portion choice.

Study 1 will test and show support for hypothesis H1, which proposes that people
behaviorally substitute food with non-food reinforcers. Further, I aim at providing
consistent behavioral evidence for this effect in Study 2, lending additional support to the
notion that reward substitution is alternative effective determinant of smaller portion
choice. However, the underlying psychological and physiological process mechanisms are
not yet understood by the behavioral studies alone. Although I will show that a money
lottery is a behaviorally effective incentive stimulus that positively reinforces consumers to
choose smaller portions (Study 1), I have not yet shed light on why and how this behavioral
effect takes place. This is the reason why Study 2, which is a behavioral choice experiment
while participants are undergoing functional magnetic resonance imaging, will be
conducted. Next, I will review important extant literature on incentive salience, a concept
that possibly explains the behavioral effectiveness of reward substitution on smaller portion
choice.

2.3. Incentive Salience: A Common Process Underlying the Effect of Reward
Substitution on Smaller Portion Choice

I propose that the non-food reinforcer paired with the half portion increases the
likelihood of consumers choosing the smaller portion, because it is similarly rewarding
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than the full portion without the non-food reinforcer. This common reward process explains
the relationship between the portion size/lottery offering and portion choice. The reward
that comes from imagining, actually seeing, or tasting food has its basis in the brain, where
it generates simultaneously yet distinguishable “liking” and “wanting” responses (Berridge,
2009). While liking is a hedonic reaction to the pleasure of a food stimulus, which is often
solely equated to reward, wanting is a psychological processes referred to as incentive
salience—a food that is perceived as incentive salient becomes attractive, attention-
grabbing, and a motivational target (Berridge & Robinson, 1998; Everitt & Robbins, 2005).
Without liking, wanting is only a partial reward without any pleasure derived from the
stimulus; without wanting, liking is simply a hedonic state without a motivational target.
As such, reward cannot occur without wanting, even in situations where liking exists
(Berridge, 2009). In order for a food stimulus to influence actual food choice, the pleasure
derived from the food must be translated into wanting (Berridge, 1996).
Functional neuroimaging research has also disentangled linking from wanting at the
brain level (Litt, Plassmann, Shiv, & Rangel, 2010). There is strong empirical evidence that
wanting is a psychological process generated in the mesolimbic dopamine system (cf.
Berridge, 2009) and, in particular, associated with increased activation of the striatum. The
mesolimbic dopamine system has its roots in the brain stem—particularly the ventral
tegmental area, where it triggers the release of the neurotransmitter dopamine upon
perception of the incentive-salient stimulus (D’Ardenne, McClure, Nystrom, & Cohen,
2008). Dopamine is subsequently projected to several different areas of the brain, including
the striatum (both its dorsal/upper and ventral/lower parts) and regions of the prefrontal
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cortex (Schultz, 2000). Figure 6
tegmental area and the striatum, which prior research has
distinct but neurophysiological
reward anticipation, reward prediction, pleasure, and euphoria as well as some of its
negative counterparts such as c
involved when wanting incentive
striatum: Kim, Shimojo, & O'Doherty, 2011; ventral striatum: Knutson, et al., 2001; dorsal
striatum: Valentin & O'Doherty, 2009)
2001), preferred products (dorsal striatum: Knutson, Rick, Wimmer, Prelec, &
Loewenstein, 2007), and aesthetic products
THE DOPAMINERGIC LIN
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Figure 6 illustrates the dopaminergic link between the ventral
tegmental area and the striatum, which prior research has associated with conceptually
distinct but neurophysiologically highly interrelated phenomena such as reward motivation,
ard prediction, pleasure, and euphoria as well as some of its
counterparts such as compulsion. Recent neuroimaging research finds the striatum
involved when wanting incentive-salient stimuli other than food, including money
striatum: Kim, Shimojo, & O'Doherty, 2011; ventral striatum: Knutson, et al., 2001; dorsal
striatum: Valentin & O'Doherty, 2009), beautiful faces (ventral striatum: Aharon, et al.,
(dorsal striatum: Knutson, Rick, Wimmer, Prelec, &
, and aesthetic products (ventral striatum: Reimann, et al., 2010)
FIGURE 6
THE DOPAMINERGIC LINK BETWEEN THE VENTRAL TEGMENTAL AREA
AND THE STRIATUM
18
illustrates the dopaminergic link between the ventral
conceptually
highly interrelated phenomena such as reward motivation,
ard prediction, pleasure, and euphoria as well as some of its
Recent neuroimaging research finds the striatum
salient stimuli other than food, including money (ventral
striatum: Kim, Shimojo, & O'Doherty, 2011; ventral striatum: Knutson, et al., 2001; dorsal
(ventral striatum: Aharon, et al.,
(dorsal striatum: Knutson, Rick, Wimmer, Prelec, &
(ventral striatum: Reimann, et al., 2010).
L TEGMENTAL AREA

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Based on the implication of the striatum in wanting incentive-salient stimuli (e.g.,
Berridge, 1996; Kim, et al., 2011; Knutson, et al., 2001; Valentin & O'Doherty, 2009), I
propose that brain activation—more specifically, blood oxygen level dependent, (BOLD)
responses—in the striatum after being confronted with the incentive-salient stimuli and
before choosing full food portions without a non-food reinforcer will significantly
“overlap” (Kim, et al., 2011) with brain activation prior to choosing half portions with such
a reinforcer. This research thus builds on the idea of a common neural currency—
mesolimbic dopamine—(Montague & Berns, 2002; Schultz, et al., 1997; Wise, 1978) and
aims to determine whether the combination of a small food portion and a non-food
reinforcer would add up in terms of striatal activation (or, indirectly, mesolimbic
dopamine) to the striatal activation of a large food portion alone. This account adds to
previous research, which has investigated overlapping activation in the mesolimbic
dopamine system for food and money (Kim, et al., 2011) but has not extended this to the
quest of getting consumers to choose smaller food portions. As such, this research builds
on the common currency idea but also applies it to research on smaller portion choices.
More specifically, I expect that such overlapping activation in the striatum will explain the
link between portion size/lottery ticket on portion choice. Therefore, it is hypothesized:

H2a: A combination of a small food portion and a non-food reinforcer
adds up in terms of striatal activation (or, indirectly, mesolimbic
dopamine) to the striatal activation of a large food portion alone,
which becomes evident in overlapping activation in the striatum.
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H2b: Overlapping activation in the striatum will precede the effect of
smaller portion choice in situations in which a smaller food portion is
paired with a non-food reinforcer similar to a full portion choice.

To test hypothesis H2, a functional magnetic resonance imaging (fMRI)
experiment is conducted. A recent status review of the domain of consumer research
predicted that “future stimulation can come from adjoining territories that are gaining
traction, such as neuroscience” (MacInnis & Folkes, 2010, p. 911). Indeed, neuroimaging
has become a useful tool for both theory development and testing in marketing and
consumer research (Reimann, Schilke, Weber, Neuhaus, & Zaichkowsky, 2011; Shiv et al.,
2005; Yoon et al., 2012), particularly for testing underlying cognitive processes (e.g.,
Adam Craig, Loureiro, Wood, & Vendemia, 2012; Dietvorst et al., 2009; Yoon, Gutchess,
Feinberg, & Polk, 2006) and affective mechanisms (e.g., Hedgcock & Rao, 2009;
Reimann, Castaño, Zaichkowsky, & Bechara, 2012; Reimann, et al., 2010). Specifically, as
discussed elsewhere (Reimann, et al., 2011), using brain imaging offers four different
methodological advantages for consumer and marketing research: (1) fMRI allows
interpretation of psychological processes in the brain as they are taking place; (2) fMRI
permits measurement of nonconscious conditions and processes; (3) fMRI enables
localization and differentiation of constructs that subjectively may seem similar but
which are actually processed differently; and (4) fMRI makes the measurement of the
simultaneous activation of two antithetical conditions and processes feasible (Reimann, et
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21
al., 2011). The following example illustrates these four advantages. A consumer being
asked for the experienced emotion on a questionnaire tends to think about this question
rather than to actually “re-feel” or “re- experience” the situation (R. Wood &
Zaichkowsky, 2004). For example, when asked about the reward or desire associated
with a food portion, a participant would access memories stored about how rewarding a
food-related experience was in the past and cognitively re-appraise a situation of food
choice. Arguably, this is not the same as actually experiencing the reward when being
confronted with a food choice, because engaging cognitive processes may distort actual
emotional processes. Aimed at capturing such emotional aspects, the specific design of
neuroimaging experiments allows the assessment of the neural correlates before, during,
and after food choice actually takes place. Moreover, fMRI permits the differentiation of
mechanisms underlying food choice, such as distinguishing wanting from liking
(Berridge, 1996; Litt, et al., 2010; Reimann, et al., 2011). These different advantages lead
to the methodological choice of incorporating a neuroimaging experiment in this
research.

2.4. Alternative Process Mechanisms
Besides the notion that a half food portion reward and non-food reward involve
similar if not greater levels of incentive salience (versus simply pleasure/liking) than the
full food portion reward alone, several different alternative process mechanisms could
provide additional explanations for why the reward substitution effect occurs. Although
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the present work does not test these alternative effects, it is important to briefly review
why these alternative explanations could come into existence.
Pleasure/liking from mere categorization versus incentive salience/wanting. First,
offering consumers an additional category (i.e., food category and non-food category)
could possibly explain the reward substitution effect. Recently, research by Mogilner,
Rudnick, and Iyengar (2008) introduced a “mere categorization effect,” which assumes
that the presence of additional categories signals differences between options to
consumers, even irrespective of the categories’ content. The authors showed that a greater
number of categories that subdivide a product assortment increased consumers’
satisfaction with their chosen option. It was also argued that this process is perceptual in
nature; hence, consumers perceive more differences in the set of available options
through the simple presence of different categories, even if the categories do not supply
information about the available options. Applying the notion of mere categorization to
the reward substitution effect examined in the present work, a possibility why consumer
could switch from the full portion alone to the bundle of half portion and non-food
reward may be the mere presence of an additional category (i.e., non-food reward)
providing them with either additional pleasure (“liking”). Indeed, Mogilner, Rudnick, and
Iyengar (2008) revealed an effect of number of categories on satisfaction, which may
have actually tapped the pleasure/liking mechanism that is inseparable from experiencing
satisfaction and happiness (Berridge & Kringelbach, 2008; Kringelbach & Berridge,
2009, 2010) but less so with incentive salience/wanting (Berridge, Robinson, & Aldridge,
2009; Smith, Berridge, & Aldridge, 2011).
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Pleasure/liking from the “thrilling” uncertainty of the lottery versus incentive
salience/wanting. Second, since the lottery that is offered as a non-food reward involves
uncertainty, the reward substitution effect could possibly also be explained through the
pleasure/liking that the “thrill” of gambling may provide. Prior research shows that the
reason consumers gamble (e.g., play the lottery or visit a casino) is because they seek
emotional “lift,” “rush”, and “thrill,” not only by winning but also through the uncertainty
of the gambling outcome, which may provide consumers with an element of pleasurable
suspense (Cotte, 1997; Loroz, 2004). Hence, feelings of uncertainty are fundamental to
any enjoyable gambling experience (Loroz, 2004). Applying this idea of thrill-based
uncertainty that is inherent in lotteries to the current research, another possibility why
consumer could have switched from the full portion alone to the bundle of half portion
and non-food reward is the level of pleasurable uncertainty that is present in the lottery.
Yet, as briefly reviewed above, one stream of research clearly distinguished
pleasure/liking from incentive salience/wanting (Berridge, et al., 2009; Smith, et al.,
2011).
Valuation versus incentive salience/wanting. Third and final, yet another
alternative process mechanism of the reward substitution effect could be that consumer
engage in simple valuation in the sense of trading-off between the two different product
options (e.g., Ostrom & Iacobucci, 1995; Wertenbroch & Dhar, 2000). If valuation is in
actuality the underlying process, than consumers should be indifferent between choosing
the full portion at, for example, $4 and the half portion offered with a coupon that offers
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$2 off on the next meal. Further, following the valuation logic, while consumer should
increasingly choose the full portion at decreasing rebate coupon amounts (e.g., from
$1.75 off to $1.50 off to $1 off) paired with the half portion, consumer should
decreasingly choose the full portion at increasing rebate coupon amounts (e.g., from
$2.25 off to $2.50 off to $3 off) paired with the half portion. While such a valuation
effect is indeed conceptually plausible, it becomes practically infeasible quickly.
Moreover, it is also unclear if valuation as an underlying process would be significantly
different from the notion of incentive salience/wanting. Indeed, a half portion paired with
a coupon that gives 50 cents is clearly less desirable than the full portion alone. In other
words, it is likely that consumers would not “want” such an offering. On the other, a half
portion with a $20 or $50 rebate off the next meal is clearly desirable for consumers but
highly undesirable from a business perspective. In summary, it can be expected that
valuation is not behaviorally inseparable from incentive salience/wanting. In other words,
no significant difference in reward substitution should stem from having consumers
engage in trade-off judgments in regard to the value of the half portion paired with a
coupon versus the full portion alone (compared to not having consumer engage in such
valuation). Yet, there may be difference in valuation and incentive salience/wanting at the
brain level. Specifically, recent research has utilized functional magnetic resonance
imaging to show that brain activation in the medial orbitofrontal, rostral anterior
cingulate, and posterior cingulate cortices was associated with valuation but not incentive
salience, whereas activation in the dorsal anterior cingulate, supplementary motor area,
insula, and the precentral and fusiform gyri was associated with incentive salience but not
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valuation (Litt, et al., 2010). Interestingly, the authors found only the ventral striatum and
the cuneus active for both valuation and incentive salience (Litt, et al., 2010); with the
striatum being the crucial for the processing of incentive salience (e.g., Berridge &
Robinson, 1998). This neuroimaging finding supports our notion of the inseparability of
valuation and incentive salience/wanting at the behavioral level. As such, it can be
expected that the reward substitution effect is not affected by valuation.
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Chapter 3.

3.1. Introduction

The aim of Study 1 is to test hypothesis H1, which states that substituting
reinforcers with non-food reinforcers determines smaller portion choice.
builds on the notion of behaviorally intertwined reinforcers, and
monetary lottery tickets can be partially substituted
smaller portions. Figure 7 illustrates the overview of Chapter 3.
THESIS OVERVIEW: CHA
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Chapter 3. Study 1: The Reward Substitution Effect
The aim of Study 1 is to test hypothesis H1, which states that substituting
food reinforcers determines smaller portion choice. This hypothesis
notion of behaviorally intertwined reinforcers, and I expect that food and
can be partially substituted to incentivize consumers to choose
illustrates the overview of Chapter 3.
FIGURE 7
THESIS OVERVIEW: CHAPTER 3
26
The aim of Study 1 is to test hypothesis H1, which states that substituting food
This hypothesis
that food and
ers to choose

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27
To test this proposition, a novel behavioral choice task, called the Fat Or Optimal
Decision (FOOD) task, was used. In this task, participants were presented several different
foods from the typical American fast food diet, including burgers, hot dogs, and tacos.
Participants were shown both the full and the half portion of these foods and asked which
one they would choose. In order to incentivize participants to choose the half portion, it
was paired with a monetary lottery ticket. Participants chose the full portion most often
when the half portion was paired with a zero dollar ticket. However, when the lottery ticket
was worth $10, participants chose the half portion significantly more often. In other words,
there was a significant decrease in the percentage of full portion choices once the half
portion was paired with a $10 lottery ticket. Furthermore, a magnitude effect was observed:
increasing the dollar amount of the lottery from $10 to $50 resulted in an additional
decrease of the full portion choice percentage. However, increasing the dollar amount from
$50 to $100 did not result in a significant additional decrease in full portion choices. This
suggests that the monetary reinforcer does not have to be exorbitantly high in order for the
reward substitution effect to work effectively. As discussed in more detail below, these
insights have potentially vital implications for introducing reward substitution to the actual
marketplace. Restaurants could sell half portions paired with lottery tickets at the same
price as full portions. This line of thought suggests opportunities for implementation. The
following sections detail the data collection and results of Study 1.

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3.2. Method

Sample. A sample of 431 individuals was drawn from an online panel of the
commercial web survey provider Qualtrics (http://www.qualtrics.com) through the
University of Southern California’s account. Participants were offered binary choices
between full-portion meals without a lottery ticket and half-portion meals with a lottery
ticket in a within-subjects, repeated-measures experiment. Once the data collection was
completed, participants who stated that their age was under 18 (five participants) were
excluded from further analyses along with those did not sufficiently respond to the online
task. The filtering is justifiable given the nature of the study, which was conducted over the
Internet with participants likely responding on their home or work computers. Therefore, it
is important to note that the experiment was not conducted in a controlled environment but
is a field study in nature with several participants not being able to satisfactorily respond.
The final dataset contained 217 adult consumers (52% female; M
age
= 43 years), which was
used in the subsequent analyses.
Stimuli. Food pictures were taken at typical American fast food restaurant chains
(e.g., McDonald’s, Burger King, Taco Bell) before a neutral background and included
adult-sized portions of standard fast food meals, including Big Mac, Burrito Supreme,
Quesadilla, Cheeseburger, Chicken Sandwich, Hot Dog, Chicken Taco, Hamburger, Pizza,
Whopper, Footlong Sandwich, and Special Hot Dog. These different foods were
photographed as full portions as they were received over the counter from each restaurant.
Figure 8 displays the full portions. Foods were then cut in half and photographed as half
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portions. The angle of photography, coloration, and the neutral background were kept
constant to ensure that the remaining difference between full and half portion photographs
was the portion size. Figure 9 displays the half portions.
The food photographs were altered by adding a black box at the bottom that
displayed the winning amount of the lottery ticket in white font (for examples, see Figures
8 and 9; black box enlarged here to increase legibility). Each full portion was always paired
with a $0 lottery ticket, which was displayed as “and win $0.” As such, there was zero
monetary winning possibility when choosing a full portion. Each half portion was paired
with one of four different lottery ticket amounts: $0, $10, $50, and $100. Figure 9 displays
the $10 condition. During the online experiment and as described in more detail below, full
and half portions of the same food type were displayed adjacent to each other in a binary
choice task that resulted in 48 trials (equal to 12 foods x 4 lottery ticket amounts).
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Note.—The full portion condition is shown here (i.e., full portion paired with $0 lottery
ticket).
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FIGURE 8
FULL PORTION STIMULI
The full portion condition is shown here (i.e., full portion paired with $0 lottery
30

The full portion condition is shown here (i.e., full portion paired with $0 lottery
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Note.—The $10 lottery ticket condition is shown
$100) are not shown here.
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FIGURE 9
HALF PORTION STIMULI
The $10 lottery ticket condition is shown here. The three other conditions ($0, $50,
31

hree other conditions ($0, $50,
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Online survey and experimental task. Before the experiment, participants reported
liking and occasionally eating the foods presented to them during the experiment.
Participants were also asked to report their self-perceived level of satiety (Wansink,
Painter, & North, 2005), age, gender, height, and weight. Participants also answered survey
items related to preferences, emotional well-being, trait impulsivity, and behavioral
inhibition/activations, as described in more detail below.
After answering the survey items, participants were routed to the experimental task,
which was coded in JavaScript. Participants entered their assigned subject identification
number and then were shown several screens of instructions. The instructions were as
follows: “Welcome to the FOOD TASK! In the following task, you will be offered foods
from well-known restaurant chains. You will always make your choice between two
options. One of the two options will include only a food item, the other option will include a
food item and sometimes the opportunity of a lottery participation. After being presented
with the food options for a few seconds, you will be prompted to choose one of the two
options by pressing "1" for Option 1 OR by pressing "2" for Option 2. The price of the two
options is equal: Option 1 is always $4 and Option 2 is always $4, too. Over the course of
the task, each food will be presented 4 times. After the task, you will receive a coupon for
the two foods you chose most often. I will deduct $8 (2 x $4) from your earnings today.
Thus, your choices are REAL! The maximum number of foods you will actually receive is 2.
If you chose a food together with a lottery, you will also participate in that lottery. I will
then notify you about your winnings after the drawings in a few weeks. Remember: First,
look at the two options. Then, choose one option by pressing 1 OR 2. < The FOOD TASK
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will start now >” Figure 10 exemplifies
their computer screen.
EXEMPLARY TASK VIEW
Participants were intentionally left
probabilities for the lottery, which was crucial
addition, this prevented participants
The experiment aimed to be as
expect (1) actual food coupons for thei
cost of the foods from their reimburs
After the study, participants received full reimbursement.
Once the choice task started
portions of 12 different foods
decision phase,” participants consider
subsequent choice. Next, participants
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exemplifies how participants saw the online experiment on
FIGURE 10
EXEMPLARY TASK VIEW ON COMPUTER SCREEN
were intentionally left in uncertainty by not disclosing winning
probabilities for the lottery, which was crucial for the experiment to mirror reality.
participants from engaging in any winning probability calculations.
to be as incentive compatible as possible by having participants
actual food coupons for their most preferred food choices, (2) a deduct
reimbursements, and (3) inclusion of their name in a lot
After the study, participants received full reimbursement.
Once the choice task started, participants were shown photos of the full and the half
different foods in pseudo-randomized order. During this six-second
participants considered the two different options and anticipate their
subsequent choice. Next, participants were prompted to choose one of the two options by
33
participants saw the online experiment on

in uncertainty by not disclosing winning
reality. In
in any winning probability calculations.
by having participants
deduction the
in a lottery.
photos of the full and the half
second “pre-
the two different options and anticipate their
to choose one of the two options by
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asking them to pick one from the above for
received a two-second confirmation of their
as “you picked 1” or “you picked 2,”
on the keyboard, the message
seconds. Participants saw a white cross
the next trial started (fixation phase).
the online experimental task.
TRIAL STRUCTURE AND

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ick one from the above for four seconds (choice phase), after which they
confirmation of their choice (confirmation phase) that was displayed
as “you picked 1” or “you picked 2,” respectively. If a participant did not press “1” or “2”
the message “no valid response from you!” was displayed for two
saw a white cross for two seconds to maintain their attention before
tion phase). Figure 11 illustrates the trial structure and timing of

FIGURE 11
TRIAL STRUCTURE AND TIMING OF ONLINE EXPERIMENTAL TASK
34
after which they
choice (confirmation phase) that was displayed
a participant did not press “1” or “2”
for two
to maintain their attention before
illustrates the trial structure and timing of
ERIMENTAL TASK

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35
Once the online experimental task was completed, participants were routed back to
the Qualtrics survey and asked to confirm the completion of the online experimental task in
order to receive their reimbursement. The data collection resulted in a usable sample of n =
217 with complete responses.

3.3. Results

Direct effect. The reward substitution effect was observed in a large dataset
obtained from a general population sample of adult consumers. Across the 12 trials per
condition, the mean choice percentage of full portions was calculated for each participant.
Then, the mean choice percentage of full portions was calculated for all 217 participants
per condition, resulting in four mean choice percentages for full portions. Three separate
paired samples t-tests were run for these four conditions. Results showed that the majority
of participants chose the full portions most often when the half portions were offered with
no ticket (mean (M) choice percentage of full portion = .56) but less frequently when the
half portions were paired with either a $10 ticket (M = .13), $50 ticket (M = .08), or $100
ticket (M = .07). The mean choice percentage of full portions decreased significantly when
half portions were paired with a $10 ticket compared to when no ticket was offered with
the half portion (t(216) = 16.59, p < .001, paired samples, effect size r = .75). The mean
choice percentage of full portions dropped even further when the half portions were offered
with a $50 rather than a $10 ticket (t(216) = 2.48, p < .05, paired samples, effect size r =
.17), providing convergent evidence for a magnitude effect. That is, increasing the winning
REWARD SUBSTITUTION

lottery amount from $10 to $50 also
half portion. However, increasing the winning amount from $50 to $100 did not
significantly increase the switch fr
decreasing additional reinforcement value for the ticket.
effect identified of Study 1.
STUDY 1: PERCENTAGE OF FULL P
INCREASING LOTTERY A
REWARD SUBSTITUTION
lottery amount from $10 to $50 also increased the number of switched choices
half portion. However, increasing the winning amount from $50 to $100 did not
significantly increase the switch from full to half portion (p > .1), supporting the
decreasing additional reinforcement value for the ticket. Figure 12 illustrates the
FIGURE 12
PERCENTAGE OF FULL PORTION CHOICE DECREASES WITH
INCREASING LOTTERY AMOUNT
36
switched choices from full to
half portion. However, increasing the winning amount from $50 to $100 did not
the effect of
illustrates the direct
SES WITH

REWARD SUBSTITUTION

37
Moderating effects. Besides analyzing the direct effect of reward substitution on
smaller food portion choice, I investigated whether several different variables moderate
or present a possible boundary condition (i.e., nullify) to the reward substitution effect. In
particular, I suspected different demographic variables (i.e., age, gender, body mass
index), the level of satiety, preference for specific food characteristics, emotional well-
being, trait impulsivity, and behavioral activation/inhibition systems to impact the reward
substitution effect. For most of these variables, I used established scale measures and
procedures to analyze their potential effects.
Further, I applied a generalized linear latent and mixed model (GLLAMM) to the
data (Rabe-Hesketh, Skrondal, & Pickles, 2004) to deal with the repeated-measures
experimental design that for each participant generated a large data file with 48 distinct
food choices. Rabe-Hesketh et al. (2004) wrote that “gllamm is a Stata program to fit
GLLAMMs (Generalized Linear Latent and Mixed Models). GLLAMMs are a class of
multilevel latent variable models for (multivariate) responses of mixed type including
continuous responses, counts, duration/survival data, dichotomous, ordered and
unordered categorical responses and rankings” (p. 1).
The lottery ticket amount (i.e., $0, $10, $50, and $100) was defined as the
independent variable (i.e., $0, $10, $50, and $100) and the actual choice response (i.e.,
full portion choice or half portion choice) was defined as dependent variable. Parts of the
choice responses were recoded from the original keyboard inputs. In particular, while the
original choice response of “1” for the full portion was kept, the original choice response
of “2” for the half portion was recoded into “0” in order for the logistic regression model
REWARD SUBSTITUTION

38
to work. The potential moderating variables were averaged per participant and then kept
as continuous variables. Figure 13 illustrates the different possible moderators, some of
which were found and some of which were not found to have a significant impact on the
relationship between monetary lottery and full food portion choice.
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STUDY 1: MODERATORS OF THE
Note.—The variables displayed in the upper part of the figure were found to
displayed in the lower part of the figure were found to have nonsignificant effects.
FIGURE 13
MODERATORS OF THE REWARD SUBSTITUTION EFFECT
The variables displayed in the upper part of the figure were found to have significant moderating effects; the variables
displayed in the lower part of the figure were found to have nonsignificant effects.
39

have significant moderating effects; the variables
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Age. First, participant age
participants. Results of the logistic regression show
full portion choice was moderated by participant age. There was a significant
interaction between lottery and age (
lottery on full portion choice was
are, the more likely that an increasing lottery ticket amount leads to fewer full portion
choices (Table 1).
AGE MODERATES THE
Note.—The variable “lotteryxage” refers to the interaction term.

Gender. Gender data were available from all 217 participants.
logistic regression show that the negative effect of the lottery on full portion choice is not
moderated by gender. As shown in Table 2,
lottery and gender (p > .4).
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participant age was assessed. Data were available from all 217
participants. Results of the logistic regression show that the negative effect of the lottery on
full portion choice was moderated by participant age. There was a significant negative
interaction between lottery and age (p < .01), suggesting that the negative effect of the
was intensified by age. In other words, the older participants
are, the more likely that an increasing lottery ticket amount leads to fewer full portion
TABLE 1
AGE MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxage” refers to the interaction term.
ata were available from all 217 participants. Results of the
logistic regression show that the negative effect of the lottery on full portion choice is not
As shown in Table 2, here was no significant interaction between
40
Data were available from all 217
the negative effect of the lottery on
negative
< .01), suggesting that the negative effect of the
der participants
are, the more likely that an increasing lottery ticket amount leads to fewer full portion
EFFECT

Results of the
logistic regression show that the negative effect of the lottery on full portion choice is not
here was no significant interaction between
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GENDER DOES NOT MODERATE
Note.—The variable “lotteryxfe

Body mass index. Participants’ height and weight
index (BMI) of each participant
calculated by translating participants’ self
and their self-reported height from feet and inches into meters (m). The following formula
for BMI calculation was used: weight
198 participants, because several participan
Results of the logistic regression show that the negative effect of the lottery on full portion
choice was moderated by participants’ BMI. There was a significant
between lottery and BMI (p < .001), suggesting that the negative effect of the lottery on full
portion choice was alleviated by BMI. In other words, the greater participants’
less likely that an increasing lottery ticket amount leads to fewer full portion choices
3).
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TABLE 2
MODERATE THE REWARD SUBSTITUTION
“lotteryxfe~e” refers to the interaction term.
articipants’ height and weight were assessed, and the body
of each participant was calculated. For each participant, the BMI
calculated by translating participants’ self-reported weight from pounds into kilograms (kg)
reported height from feet and inches into meters (m). The following formula
for BMI calculation was used: weight [kg] / (height [m]
2
). Data were available from only
because several participants did not report their height and/or
Results of the logistic regression show that the negative effect of the lottery on full portion
ted by participants’ BMI. There was a significant positive interaction
< .001), suggesting that the negative effect of the lottery on full
portion choice was alleviated by BMI. In other words, the greater participants’
less likely that an increasing lottery ticket amount leads to fewer full portion choices
41
REWARD SUBSTITUTION EFFECT

and the body mass
was
reported weight from pounds into kilograms (kg)
reported height from feet and inches into meters (m). The following formula
Data were available from only
and/or weight.
Results of the logistic regression show that the negative effect of the lottery on full portion
interaction
< .001), suggesting that the negative effect of the lottery on full
portion choice was alleviated by BMI. In other words, the greater participants’ BMI are, the
less likely that an increasing lottery ticket amount leads to fewer full portion choices (Table
REWARD SUBSTITUTION

BMI MODERATES THE
Note.—The variable “bmi” is the abbreviation for
“lotteryxbmi” refers to the interaction term.

Satiety. The state of hunger is a powerful motivator
satiety level was examined using the self
2005), which contain four items assessed on a nine
little”) to 9 (“A lot”). Items were: “
right now?,” “How nauseated are you right now?
could eat right now?” Items were recoded to reflect the same direction
across the four items was calculated for each participant.
from all 217 participants. Results of the logistic regression show that the negative effect of
the lottery on full portion choice
shows no significant interaction between lottery and self
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TABLE 3
BMI MODERATES THE REWARD SUBSTITUTION EFFECT
is the abbreviation for body-mass -index. The variable
refers to the interaction term.
The state of hunger is a powerful motivator for seeking food. Participants’
using the self-perception of satiety (SPS) scale (Wansink, et al.,
, which contain four items assessed on a nine-point Likert-type scale from 1 (“
”). Items were: “How hungry are you right now?,” “How full are you
How nauseated are you right now?,” and “How much food do you think you
” Items were recoded to reflect the same direction, and the mean
across the four items was calculated for each participant. Averaged data were available
from all 217 participants. Results of the logistic regression show that the negative effect of
the lottery on full portion choice was not moderated by self-perceived satiety.
no significant interaction between lottery and self-perceptions of satiety (
42
EFFECT

The variable
. Participants’
(Wansink, et al.,
type scale from 1 (“A
How full are you
How much food do you think you
and the mean
were available
from all 217 participants. Results of the logistic regression show that the negative effect of
perceived satiety. Table 4
perceptions of satiety (p > .9).
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SATIETY DOES NOT MOD
Note.—The variable “sps” is the abbreviation for self
“lotteryxsps” refers to the interaction term.

Arguably, the choice of different foods is highly subjective and dependent on
specific consumers’ preferences, which may widely vary between consumers. As such,
consumers’ preferences for specific food characteristics
asked about the importance of
terms of preparation). Specifically,
food choice questionnaire developed by Steptoe, Pollard, and Wardle
found that these 36 items load onto nine distinct factors
sensory appeal, natural content, price, weight control, familiarity, and ethical c
(Steptoe, et al., 1995).
Importance of food being healthy
whether “It is important to me that the food I eat on a typical day
following items to be rated on a four
to 4 (“very important”). In the original work of Steptoe et al.
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TABLE 4
SATIETY DOES NOT MODERATE THE REWARD SUBSTITUTION
The variable “sps” is the abbreviation for self-perception of satiety. The variable
“lotteryxsps” refers to the interaction term.
the choice of different foods is highly subjective and dependent on
consumers’ preferences, which may widely vary between consumers. As such,
consumers’ preferences for specific food characteristics were assessed. Participants were
importance of certain food characteristics (e.g., food being convenient in
terms of preparation). Specifically, participants responded to the 36 items of the
food choice questionnaire developed by Steptoe, Pollard, and Wardle (1995). The authors
36 items load onto nine distinct factors: health, mood, convenience,
sensory appeal, natural content, price, weight control, familiarity, and ethical c
being healthy. The food choice questionnaire asks participants
It is important to me that the food I eat on a typical day” and then lists the
following items to be rated on a four-point Likert-type scale from 1 (“not at all important
”). In the original work of Steptoe et al. (1995), the “health”
43
REWARD SUBSTITUTION EFFECT

perception of satiety. The variable
the choice of different foods is highly subjective and dependent on
consumers’ preferences, which may widely vary between consumers. As such,
were assessed. Participants were
being convenient in
items of the so-called
The authors
health, mood, convenience,
sensory appeal, natural content, price, weight control, familiarity, and ethical concern
participants
and then lists the
not at all important”)
, the “health” factor
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consisted of the following items:
healthy,” “is nutritious,” “is high in protein
and “is high in fiber and roughage
data were available from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
food being healthy. There was a significant
importance of food being healthy (
on full portion choice was intensified by the importance of food being healthy. In other
words, the more emphasis participants place on food being healthy, the more likely that an
increasing lottery ticket amount leads to fewer full portion choices
IMPORTANCE OF FOOD B
MODERATES THE
Note.—The variable “lotteryxhe

Importance of food being able to
of the following items: “helps me cope with stress
relax,” “keeps me awake/alert
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the following items: “contains a lot of vitamins and minerals,” “keeps me
is high in protein,” “is good for my skin/teeth/hair/nails etc.
is high in fiber and roughage.” Items were averaged for each participant.
were available from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
here was a significant negative interaction between lottery and the
importance of food being healthy (p < .05), suggesting that the negative effect of the lottery
on full portion choice was intensified by the importance of food being healthy. In other
s, the more emphasis participants place on food being healthy, the more likely that an
increasing lottery ticket amount leads to fewer full portion choices (Table 5).
TABLE 5
IMPORTANCE OF FOOD BEING HEALTHY
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxhe~h” refers to the interaction term.
being able to lead to good mood. The “mood” factor
helps me cope with stress,” helps me to cope with life,” “
awake/alert,” “cheers me up,” and “makes me feel good.” The same
44
keeps me
is good for my skin/teeth/hair/nails etc.,”
. Averaged
were available from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
interaction between lottery and the
< .05), suggesting that the negative effect of the lottery
on full portion choice was intensified by the importance of food being healthy. In other
s, the more emphasis participants place on food being healthy, the more likely that an

factor consisted
,” “helps me
The same
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approach was used to calculate
available from all 217 participants. Results of the logistic regression show that the negative
effect of the lottery on full portion choice was moderated by
able to lead to a good mood. There was a significant
and the importance of food being able to lead to a good mood
the negative effect of the lottery on full portion choice was alleviated by
food being able to lead to a good mood
place on “mood foods,” the less likely that an increasing lottery ticket amount leads to
fewer full portion choices (Table
IMPORTANCE OF FOOD B
MODERATES THE
Note.—The variable “lotteryxmood

Importance of food being convenient
following items: “is easy to prepare
prepare,” “can be bought in shops close to where i live or work
shops and supermarkets.” The same approach for
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was used to calculate the factor’s mean per participant. Averaged data were
participants. Results of the logistic regression show that the negative
effect of the lottery on full portion choice was moderated by the importance of food being
. There was a significant positive interaction between lottery
the importance of food being able to lead to a good mood (p < .001), suggesting that
the negative effect of the lottery on full portion choice was alleviated by the importance of
food being able to lead to a good mood. In other words, the more emphasis participants
the less likely that an increasing lottery ticket amount leads to
Table 6).
TABLE 6
IMPORTANCE OF FOOD BEING ABLE TO LEAD TO GOOD MOOD
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxmood” refers to the interaction term.
food being convenient. The “convenience” factor consisted of the
is easy to prepare,” “can be cooked very simply,” “takes no time to
shops close to where i live or work,” and “is easily available in
The same approach for calculating the factor’s mean per
45
ata were
participants. Results of the logistic regression show that the negative
the importance of food being
interaction between lottery
< .001), suggesting that
the importance of
articipants
the less likely that an increasing lottery ticket amount leads to
GOOD MOOD

consisted of the
takes no time to
is easily available in
s mean per
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participant. Averaged data were available
regression show that the negative effect of the lottery on full portion choice was
moderated by the importance of food being
interaction between lottery and the importance of food being
IMPORTANCE OF FOOD B
DOES NOT MODERATE
Note.—The variable “lotteryxco

Importance of food being sensory
of the following items: “smells nice
good.” Again, the same approach
Averaged data were available
show that the negative effect of the lottery on full portion choice was
importance of food being sensory appealing.
between lottery and the importance of food being
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Averaged data were available from all 217 participants. Results of the logistic
that the negative effect of the lottery on full portion choice was
moderated by the importance of food being convenient. Table 7 reveals no significant
interaction between lottery and the importance of food being convenient (p > .6).
TABLE 7
IMPORTANCE OF FOOD BEING CONVENIENT
DOES NOT MODERATE THE REWARD SUBSTITUTION EFFECT
otteryxco~e” refers to the interaction term.
Importance of food being sensory appealing. The factor “sensory appeal
smells nice,” “looks nice,” “has a pleasant texture,” and “
Again, the same approach was used to calculate the factor’s mean per participant
Averaged data were available from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was not moderated by the
sensory appealing. Table 8 shows no significant interaction
and the importance of food being sensory appealing (p > .6).
46
from all 217 participants. Results of the logistic
that the negative effect of the lottery on full portion choice was not
significant
> .6).
EFFECT

ppeal” consisted
,” and “tastes
s mean per participant.
from all 217 participants. Results of the logistic regression
moderated by the
significant interaction

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IMPORTANCE OF FOOD B
DOES NOT MODERATE
Note.—The variable “lotteryxse

Importance of food being natural
following items: “contains no additives
artificial ingredients.” The factor’s
were available from all 217 participants. Results of the logistic regression show that the
negative effect of the lottery on full portion choice was
food being natural. Table 9 shows
importance of food being natural
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TABLE 8
IMPORTANCE OF FOOD BEING SENSORICALLY APPEALING
DOES NOT MODERATE THE REWARD SUBSTITUTION EFFECT
“lotteryxse~y” refers to the interaction term.
being natural. The “natural content” factor consisted of the
contains no additives,” “contains natural ingredients,” and “
The factor’s mean was calculated per participant. Averaged data
from all 217 participants. Results of the logistic regression show that the
negative effect of the lottery on full portion choice was not moderated by the importance of
Table 9 shows no significant interaction between lottery and the
natural (p > .1).
47
NG
EFFECT

consisted of the
,” and “contains no
Averaged data
from all 217 participants. Results of the logistic regression show that the
moderated by the importance of
significant interaction between lottery and the
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IMPORTANCE OF FOOD B
DOES NOT MODERATE
Note.—The variable “lotteryxna

Importance of food being
the following items: “is not expensive
Averaged data were available
show that the negative effect of the lottery on full portion choice was moderated by the
importance of food being attainable at a low price
interaction between lottery and the importance of food being
.05), suggesting that the negative effect of the lottery on full portion choice was alleviated
by the importance of food being
emphasis participants place on food being
lottery ticket amount leads to fewer full portion choices
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TABLE 9
IMPORTANCE OF FOOD BEING NATURAL
DOES NOT MODERATE THE REWARD SUBSTITUTION EFFECT
“lotteryxna~l” refers to the interaction term.
being attainable at a low price. The “price” factor
is not expensive,” “is cheap,” and “is good value for money
Averaged data were available from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by the
attainable at a low price. There was a significant positive
lottery and the importance of food being attainable at a low price
), suggesting that the negative effect of the lottery on full portion choice was alleviated
by the importance of food being attainable at a low price. In other words, the more
asis participants place on food being inexpensive, the less likely that an increasing
lottery ticket amount leads to fewer full portion choices (Table 10).
48
EFFECT

factor consisted of
is good value for money.”
from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by the
. There was a significant positive
attainable at a low price (p <
), suggesting that the negative effect of the lottery on full portion choice was alleviated
more
, the less likely that an increasing
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IMPORTANCE OF FOOD B
MODERATES THE
Note.—The variable “lotteryxpr

Importance of food being
of the following items: “is low in calories
fat.” The same approach was used to calculate
data were available from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
food being weight-controlling
and the importance of food being
negative effect of the lottery on full portion choice was intensified by the importance of
food being weight-controlling
food being able to help them to control weight
ticket amount leads to fewer full portion choices
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TABLE 10
IMPORTANCE OF FOOD BEING ATTAINABLE AT A LOW PRICE
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxpr~e” refers to the interaction term.
Importance of food being weight-controlling. The “weight control” factor
is low in calories,” “helps me control my weight,” and “
was used to calculate the factor’s mean per participant
from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
controlling. There was a significant negative interaction between lotter
and the importance of food being weight-controlling (p < .001), suggesting that the
negative effect of the lottery on full portion choice was intensified by the importance of
controlling. In other words, the more emphasis participants p
them to control weight, the more likely that an increasing lottery
ticket amount leads to fewer full portion choices (Table 11).
49
PRICE

factor consisted
,” and “is low in
s mean per participant. Averaged
from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by the importance of
. There was a significant negative interaction between lottery
), suggesting that the
negative effect of the lottery on full portion choice was intensified by the importance of
. In other words, the more emphasis participants place on
, the more likely that an increasing lottery
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IMPORTANCE OF FOOD B
MODERATES THE
Note.—The variable “lotteryxew

Importance of food being familiar
following items: “is what i usually eat
was a child.” The factor’s mean
available from all 217 participants. Results of the logistic regression show that the negative
effect of the lottery on full portion choice was moderated by the importance of food bei
familiar. There was a significant positive interaction between lottery and the importance of
food being familiar (p < .01), suggesting that the negative effect of the lottery on full
portion choice was alleviated by the importance of food being
more emphasis participants place on food being
ticket amount leads to fewer full portion choices
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TABLE 11
IMPORTANCE OF FOOD BEING WEIGHT-CONTROLLING
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxew~t” refers to the interaction term.
being familiar. The “familiarity” factor consisted of the
is what i usually eat,” “is familiar,” and” “is like the food i ate when i
mean was calculated per participant, and averaged data were
from all 217 participants. Results of the logistic regression show that the negative
effect of the lottery on full portion choice was moderated by the importance of food bei
. There was a significant positive interaction between lottery and the importance of
1), suggesting that the negative effect of the lottery on full
portion choice was alleviated by the importance of food being familiar. In other words,
more emphasis participants place on food being familiar, the less that an increasing lottery
ticket amount leads to fewer full portion choices (Table 12).
50
CONTROLLING

consisted of the
is like the food i ate when i
veraged data were
from all 217 participants. Results of the logistic regression show that the negative
effect of the lottery on full portion choice was moderated by the importance of food being
. There was a significant positive interaction between lottery and the importance of
1), suggesting that the negative effect of the lottery on full
. In other words, the
, the less that an increasing lottery
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IMPORTANCE OF FOOD B
MODERATES THE
Note.—The variable “lotteryxfa

Importance of food being ethical
following items: “comes from countries i approve of politically
clearly marked,” and “is packaged in an environmentally friendly way
was calculated for each participant,
participants. Results of the logistic regression show that the negative effect of the lottery
full portion choice was not moderated by the importance of food being
shows no significant interaction between lottery and the importance of food being
> .3).
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TABLE 12
IMPORTANCE OF FOOD BEING FAMILIAR
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxfa~y” refers to the interaction term.
being ethical. The “ethical concern” factor consisted of the
comes from countries i approve of politically,” “has the country of origin
is packaged in an environmentally friendly way.” Again, the mean
participant, and averaged data were available from all 217
participants. Results of the logistic regression show that the negative effect of the lottery
moderated by the importance of food being ethical.
significant interaction between lottery and the importance of food being
51

consisted of the
has the country of origin
Again, the mean
from all 217
participants. Results of the logistic regression show that the negative effect of the lottery on
ethical. Table 13
significant interaction between lottery and the importance of food being ethical (p
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IMPORTANCE OF FOOD B
DOES NOT MODERATE
Note.—The variable “lotteryxet

Positive vs. negative emotion.
Watson and Clark’s (1999) expanded form of the positive and negative affect schedule
(PANAS-X). The goal was to identify the current
to investigate whether the reward substitution
negative affect, two factors that have emerged consistently as the core dimensions of
people’s emotional experience
Participants read the following statement
phrases that describe different feelings and emotions. Read each item and then mark the
appropriate answer in the space next to that word. Indicate to what extent you feel this way
right now.” Following the instructions, participants rated
point Likert-type scale from 1 (“
(2) disgusted, (3) attentive, (4)
(9) scornful, (10) relaxed, (11)
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TABLE 13
IMPORTANCE OF FOOD BEING ETHICAL
DOES NOT MODERATE THE REWARD SUBSTITUTION EFFECT
“lotteryxet~l” refers to the interaction term.
Positive vs. negative emotion. Participants’ emotional states was assessed using
expanded form of the positive and negative affect schedule
The goal was to identify the current basic emotional state of participants
reward substitution effect is moderated by positive and/or
negative affect, two factors that have emerged consistently as the core dimensions of
people’s emotional experience (Watson & Clark, 1999; Watson, Clark, & Tellegen, 1988)
the following statement: “This scale consists of a number of words and
phrases that describe different feelings and emotions. Read each item and then mark the
appropriate answer in the space next to that word. Indicate to what extent you feel this way
Following the instructions, participants rated the following 60 items on a
type scale from 1 (“very slightly”) to 5 (“extremely or not at all”):
, (4) bashful, (5) sluggish, (6) daring, (7) surprised, (8)
, (11) irritable, (12) delighted, (13) inspired, (14) fearless
52
EFFECT

was assessed using
expanded form of the positive and negative affect schedule
state of participants and
positive and/or
negative affect, two factors that have emerged consistently as the core dimensions of
(Watson & Clark, 1999; Watson, Clark, & Tellegen, 1988).
This scale consists of a number of words and
phrases that describe different feelings and emotions. Read each item and then mark the
appropriate answer in the space next to that word. Indicate to what extent you feel this way
60 items on a five-
: (1) cheerful,
, (8) strong,
fearless, (15)
REWARD SUBSTITUTION

53
disgusted with self, (16) sad, (17) calm, (18) afraid, (19) tired, (20) amazed, (21) shaky,
(22) happy, (23) timid, (24) alone, (25) alert, (26) upset, (27) angry, (28) bold, (29) blue,
(30) shy, (31) active, (32) guilty, (33) joyful, (34) nervous, (35) lonely, (36) sleepy, (37)
excited, (38) hostile, (39) proud, (40) jittery, (41) lively, (42) ashamed, (43) at ease, (44)
scared, (45) drowsy, (46) angry at self, (47) enthusiastic, (48) downhearted, (49) sheepish,
(50) distressed, (51) blameworthy, (52) determined, (53) frightened, (54) astonished, (55)
interested, (56) loathing, (57) confident, (58) energetic, (59) concentrating, and (60)
dissatisfied with self. The focus was on the two core dimensions of affect: basic negative
affect, which includes the sub-dimensions of fear, hostility, guilt, and sadness, and positive
negative affect, which includes the sub-dimensions joviality, self-assurance, and
attentiveness.
Positive affect. Following the approach of Watson and Clark (1999), basic positive
affect was calculated as the average of joviality (i.e., happy, joyful, delighted, cheerful,
excited, enthusiastic, lively, energetic), self-assurance (i.e., proud, strong, confident, bold,
daring, fearless), and attentiveness (i.e., alert, attentive, concentrating, determined).
Averaged data were available from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by basic
positive affect. There was a significant negative interaction between lottery and positive
affect (p < .01), suggesting that the negative effect of the lottery on full portion choice was
intensified by positive affect. In other words, the more positive affect that participants
experience prior to making their food choices, the more likely that an increasing lottery
ticket amount leads to fewer full portion choices (Table 14).
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POSITIVE AFFECT MODE
Note.—The variable “lotteryx

Negative affect. Following Watson and Clark
calculated as the average of fear
hostility (i.e., angry, hostile, irritable, scornful, disgusted, loathing),
ashamed, blameworthy, angry at self, disgusted w
sadness (i.e., sad, blue, downhearted, alone, lonely).
participant, and averaged data were available
logistic regression show that the negative ef
moderated by basic negative affect
lottery and negative affect (p < .0
portion choice was alleviated by
participants experience prior to making their food choices
lottery ticket amount leads to fewer full portion choices. Table
REWARD SUBSTITUTION
TABLE 14
POSITIVE AFFECT MODERATES THE REWARD SUBSTITUTION
xba~s” refers to the interaction term.
Following Watson and Clark (1999), basic negative affect was
fear (i.e., afraid, scared, frightened, nervous, jittery, shaky),
angry, hostile, irritable, scornful, disgusted, loathing), guilt (i.e.,
ashamed, blameworthy, angry at self, disgusted with self, dissatisfied with self), and
sad, blue, downhearted, alone, lonely). Items were averaged for each
veraged data were available from all 217 participants. Results of the
logistic regression show that the negative effect of the lottery on full portion choice was
basic negative affect. There was a significant positive interaction between
< .01), suggesting that the negative effect of the lottery on full
portion choice was alleviated by negative affect. In other words, the more negative affect
participants experience prior to making their food choices, the less likely that an increasing
ticket amount leads to fewer full portion choices. Table 15 summarizes the results.
54
EFFECT

tive affect was
afraid, scared, frightened, nervous, jittery, shaky),
i.e., guilty,
ith self, dissatisfied with self), and
Items were averaged for each
from all 217 participants. Results of the
fect of the lottery on full portion choice was
. There was a significant positive interaction between
1), suggesting that the negative effect of the lottery on full
the more negative affect
, the less likely that an increasing
summarizes the results.
REWARD SUBSTITUTION

NEGATIVE AFFECT MODERATES THE
Note.—The variable “lotteryxba

Satisfaction with life. While the PANAS
states, life satisfaction was assessed
developed by Diener, Emmons, Larsen, and Griffin
“choose the extent to which you disagree or agree with the following statements about
life:” Items were rated on a five
(“totally agree”) and included
ideal,” “The conditions of my life are excellent
have gotten the important things I want in my life
change almost nothing.” During the actual online survey, the SWLS was administered after
participants responded to items on BIS/BAS (reported later).
from all 217 participants. Results of the logistic regression show that the negative effect of
the lottery on full portion choice was moderated by satisfaction with life. There was a
significant negative interaction between lottery and
suggesting that the negative effect of the lottery on full portion choice was intensified by
REWARD SUBSTITUTION
TABLE 15
MODERATES THE REWARD SUBSTITUTION
The variable “lotteryxba~g” refers to the interaction term.
While the PANAS-X schedule assessed current emotional
was assessed by means of the Satisfaction with Life Scale
developed by Diener, Emmons, Larsen, and Griffin (1985). Participants were instructed to
the extent to which you disagree or agree with the following statements about
” Items were rated on a five-point Likert-type scale from 1 (“totally disagree
”) and included the following statement: “In most ways my life is close to
The conditions of my life are excellent,” “I am satisfied with my life”, “
have gotten the important things I want in my life,” and “If I could live my life over, I would
uring the actual online survey, the SWLS was administered after
participants responded to items on BIS/BAS (reported later). Averaged data were available
from all 217 participants. Results of the logistic regression show that the negative effect of
tery on full portion choice was moderated by satisfaction with life. There was a
significant negative interaction between lottery and satisfaction with life (p < .05),
suggesting that the negative effect of the lottery on full portion choice was intensified by
55
REWARD SUBSTITUTION EFFECT

schedule assessed current emotional
Life Scale (SWLS)
Participants were instructed to
the extent to which you disagree or agree with the following statements about
totally disagree”) to 5
In most ways my life is close to
”, “So far I
If I could live my life over, I would
uring the actual online survey, the SWLS was administered after
Averaged data were available
from all 217 participants. Results of the logistic regression show that the negative effect of
tery on full portion choice was moderated by satisfaction with life. There was a
.05),
suggesting that the negative effect of the lottery on full portion choice was intensified by
REWARD SUBSTITUTION

life satisfaction. In other words, the
likely that an increasing lottery ticket amount leads to f
provides additional support to the earlier finding that
impacts the reward substitution
MODERATES THE
Note.—The variable “swls” is the abbreviation for “satisfaction with life scale.” The
variable “lotteryxswls” refers to the interaction term.

Overall impulsivity. D
item measure that was developed
Barratt (1995). Participants were given
ways they act and think in different situations. This is a test to measure some of the ways in
which you act and think. Read each statement and choose the appropriate answer in the
space next to that statement. Do not spend too muc
and honestly.” Impulsivity was assessed
“occasionally,” “often,” and “
REWARD SUBSTITUTION
. In other words, the more satisfied participants are with their lives
likely that an increasing lottery ticket amount leads to fewer full portion choices.
provides additional support to the earlier finding that states of positive affect negatively
reward substitution effect (Table 16).
TABLE 16
SATISFACTION WITH LIFE
MODERATES THE REWARD SUBSTITUTION EFFECT
The variable “swls” is the abbreviation for “satisfaction with life scale.” The
variable “lotteryxswls” refers to the interaction term.
Data on participants’ impulsivity were assessed using the 30
that was developed by Barratt (1959) and honed by Patton, Stanford, and
were given the following instructions: “People differ in the
ways they act and think in different situations. This is a test to measure some of the ways in
which you act and think. Read each statement and choose the appropriate answer in the
space next to that statement. Do not spend too much time on any statement. Answer quickly
was assessed on a four-point scale (“rarely/never,”
,” and “almost always/always”). Items were: (1) “I plan tasks
56
lives, the more
ewer full portion choices. This
negatively

The variable “swls” is the abbreviation for “satisfaction with life scale.” The
using the 30-
and honed by Patton, Stanford, and
People differ in the
ways they act and think in different situations. This is a test to measure some of the ways in
which you act and think. Read each statement and choose the appropriate answer in the
h time on any statement. Answer quickly
,”
plan tasks
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57
carefully,” (2) “I do things without thinking,” (3) “I make-up my mind quickly,” (4) “I am
happy-go-lucky,” (5) “I don’t “pay attention”,” (6) “I have “racing” thoughts,” (7) “I plan
trips well ahead of time,” (8) “I am self controlled,” (9) “I concentrate easily,” (10) “I save
regularly,” (11) “I ‘squirm’ at plays or lectures,” (12) “I am a careful thinker,” (13) “I plan
for job security,” (14) “I say things without thinking,” (15) “I like to think about complex
problems,” (16) “I change jobs,” (17) “I act ‘on impulse’,” (18) “I get easily bored when
solving thought problems,” (19) “I act on the spur of the moment,” (20) “I am a steady
thinker,” (21) “I change residences,” (22) “I buy things on impulse,” (23) “I can only think
about one thing at a time,” (24) “I change hobbies,” (25) “I spend or charge more than I
earn,” (26) “I often have extraneous thoughts when thinking,” (27) “I am more interested
in the present than the future,” (28) “I am restless at the theater or lectures,” (29) “I like
puzzles,” and (30) “I am future oriented.” Items were averaged for each participant, and
averaged data were available from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by overall
impulsivity. There was a significant positive interaction between lottery and overall
impulsivity (p < .001), suggesting that the negative effect of the lottery on full portion
choice was alleviated by overall impulsivity. In other words, the more impulsive
participants are, the less likely that an increasing lottery ticket amount leads to fewer full
portion choices (Table 17).
REWARD SUBSTITUTION

MODERATES THE
Note.—The variable “first_orde
referred to as the first-order factor of impulsivity
“lotteryxmood” refers to the interaction term.

In their revised version of the Barratt impulsivity scale, Patton, Stanford, and
Barratt (1995) investigated the
authors identified six distinct
cognitive complexity, perseverance, and cognitive instability.
Attention. The “attention”
(32) and refers to “focusing on the task at hand”
data were available from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by
FOOD task. There was a significant positive interaction betwee
.05), suggesting that the negative effect of the lottery on full portion choice was alleviated
REWARD SUBSTITUTION
TABLE 17
OVERALL IMPULSIVITY
MODERATES THE REWARD SUBSTITUTION EFFECT
“first_orde~r” refers to overall impulsivity, which is sometimes
order factor of impulsivity (Patton, et al., 1995). The variable
refers to the interaction term.
In their revised version of the Barratt impulsivity scale, Patton, Stanford, and
d the sub-factor structure of the overall impulsivity measure. The
authors identified six distinct sub-factors: attention, motor impulsiveness, self-
perseverance, and cognitive instability.
. The “attention” factor was measured by items (5), (9), (11), (21)
(32) and refers to “focusing on the task at hand” (Patton, et al., 1995, p. 770). Averaged
from all 217 participants. Results of the logistic regression show that
the negative effect of the lottery on full portion choice was moderated by attention on the
. There was a significant positive interaction between lottery and attention
), suggesting that the negative effect of the lottery on full portion choice was alleviated
58

r” refers to overall impulsivity, which is sometimes
The variable
In their revised version of the Barratt impulsivity scale, Patton, Stanford, and
factor structure of the overall impulsivity measure. The
-control,
(9), (11), (21), and
Averaged
from all 217 participants. Results of the logistic regression show that
attention on the
attention (p <
), suggesting that the negative effect of the lottery on full portion choice was alleviated
REWARD SUBSTITUTION

by attention. In other words, the
increasing lottery ticket amount leads to
ATTENTION MODERATES THE
Note.—The variable “lotteryxat

Motor impulsiveness. The “motor
(3), (4), (17), (20), (23), and (28) and
(Patton, et al., 1995, p. 770). Averaged data we
Results of the logistic regression show that the negative effect of the lottery on full portion
choice was moderated by motor impulsiveness
interaction between lottery and
negative effect of the lottery on full portion choice was alleviated by motor impulsiveness.
In other words, the more motor
lottery ticket amount leads to fewer full portion choices
REWARD SUBSTITUTION
the more attention participants pay, the less likely that an
increasing lottery ticket amount leads to fewer full portion choices (Table 18).
TABLE 18
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxat~n” refers to the interaction term.
. The “motor impulsiveness” factor was measured by
(3), (4), (17), (20), (23), and (28) and defined as “acting on the spur of the moment”
Averaged data were available from all 217 participants.
Results of the logistic regression show that the negative effect of the lottery on full portion
motor impulsiveness. There was a marginally significant
interaction between lottery and motor impulsiveness (p = .065), suggesting that the
negative effect of the lottery on full portion choice was alleviated by motor impulsiveness.
In other words, the more motor-impulsive participants are, the less likely that an increasing
lottery ticket amount leads to fewer full portion choices (Table 19).
59
, the less likely that an

EFFECT

was measured by items (2),
as “acting on the spur of the moment”
from all 217 participants.
Results of the logistic regression show that the negative effect of the lottery on full portion
significant positive
, suggesting that the
negative effect of the lottery on full portion choice was alleviated by motor impulsiveness.
t an increasing
REWARD SUBSTITUTION

MOTOR IMPULSIVITY
THE REWARD SUBSTITUTION
Note.—The variable “lotteryxmo
that motor impulsivity’s effect is marginally significant at a

Self-control. The factor “self
(13), and (14) and refers to “planning and thinking carefully”
Averaged data were available
show that the negative effect of the lottery on full portion choice was moderated by
control. There was a significant positive interaction between lottery and
.001), suggesting that the negative effect of the lottery on full port
by self-control. In other words, more
increasing lottery ticket amount leads to fewer full portion choices
REWARD SUBSTITUTION
TABLE 19
MOTOR IMPULSIVITY MODERATES
REWARD SUBSTITUTION EFFECT
“lotteryxmo~r” refers to the interaction term. It is important to note
that motor impulsivity’s effect is marginally significant at a p-level of .065.
. The factor “self-control” was measured by items (1), (7), (8), (12),
(13), and (14) and refers to “planning and thinking carefully” (Patton, et al., 1995, p. 770)
Averaged data were available from all 217 participants. Results of the logistic regression
ative effect of the lottery on full portion choice was moderated by
. There was a significant positive interaction between lottery and self-control
.001), suggesting that the negative effect of the lottery on full portion choice was
. In other words, more self-controlled participants are, the less likely that an
increasing lottery ticket amount leads to fewer full portion choices (Table 20).
60

It is important to note
(1), (7), (8), (12),
(Patton, et al., 1995, p. 770).
from all 217 participants. Results of the logistic regression
ative effect of the lottery on full portion choice was moderated by self-
control (p <
ion choice was alleviated
, the less likely that an

REWARD SUBSTITUTION

SELF-CONTROL MODERATES THE
Note.—The variable “lotteryxself

Cognitive complexity. The “cognitive complexity”
(10), (15), (18), (31), and (33) and
et al., 1995, p. 770). Averaged data were available
logistic regression show that the negative effect of the lottery on full portion choice was
moderated by cognitive complexity
lottery and cognitive complexity
lottery on full portion choice was alleviated by
participants enjoy challenging mental tasks with high cognitive complexity
that an increasing lottery ticket amount leads to fewer full portion choices
REWARD SUBSTITUTION
TABLE 20
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxself” refers to the interaction term.
. The “cognitive complexity” factor was measured by items
(33) and defined as enjoying “challenging mental tasks”
Averaged data were available from all 217 participants. Results of the
logistic regression show that the negative effect of the lottery on full portion choice was
cognitive complexity. There was a significant positive interaction between
cognitive complexity (p < .001), suggesting that the negative effect of the
lottery on full portion choice was alleviated by cognitive complexity. In other words,
participants enjoy challenging mental tasks with high cognitive complexity, the less likely
lottery ticket amount leads to fewer full portion choices (Table
61
EFFECT

was measured by items
as enjoying “challenging mental tasks” (Patton,
from all 217 participants. Results of the
logistic regression show that the negative effect of the lottery on full portion choice was
. There was a significant positive interaction between
< .001), suggesting that the negative effect of the
. In other words, the
, the less likely
Table 21).
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MODERATES THE
Note.—The variable “lotteryxco

Perseverance. The “perseverance”
and (34) and refers to “a consistent life style”
were available from all 217 participants. Results of the logistic regression show that the
negative effect of the lottery on full portion choice was moderated by
was a significant positive interaction between lottery and
suggesting that the negative effect of the lottery on full portion choice was alleviated by
perseverance. In other words,
increasing lottery ticket amount leads to fewer full portion choic
REWARD SUBSTITUTION
TABLE 21
COGNITIVE COMPLEXITY
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxco~x” refers to the interaction term.
. The “perseverance” factor was measured by items (16),
(34) and refers to “a consistent life style” (Patton, et al., 1995, p. 770). Averaged data
from all 217 participants. Results of the logistic regression show that the
negative effect of the lottery on full portion choice was moderated by perseverance
was a significant positive interaction between lottery and perseverance (p < .001),
suggesting that the negative effect of the lottery on full portion choice was alleviated by
. In other words, the more perseverant participants are, the less likely that an
increasing lottery ticket amount leads to fewer full portion choices (Table 22).
62

, (22), (24),
Averaged data
from all 217 participants. Results of the logistic regression show that the
perseverance. There
01),
suggesting that the negative effect of the lottery on full portion choice was alleviated by
, the less likely that an

REWARD SUBSTITUTION

PERSEVERANCE MODERATES THE
Note.—The variable “lotteryxpe~

Cognitive instability. The “cognitive instability”
(25), and (30) and refers to “thought insertions and racing thoughts”
770). Averaged data were available
regression show that the negative effect of the lottery on full portion choice was moderated
by cognitive instability. There was a significant negative interaction between lottery and
cognitive instability (p < .05), suggesting that the negative effect of the lottery on full
portion choice was intensified by
instable participants are, the more likely that an increasing lottery ticket amount leads to
fewer full portion choices (Table
REWARD SUBSTITUTION
TABLE 22
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxpe~e” refers to the interaction term.
. The “cognitive instability” factor was measured by items
(30) and refers to “thought insertions and racing thoughts” (Patton, et al., 1995, p.
Averaged data were available from all 217 participants. Results of the logistic
regression show that the negative effect of the lottery on full portion choice was moderated
. There was a significant negative interaction between lottery and
.05), suggesting that the negative effect of the lottery on full
portion choice was intensified by cognitive instability. In other words, the cognitively
, the more likely that an increasing lottery ticket amount leads to
Table 23).
63
EFFECT

was measured by items (6),
(Patton, et al., 1995, p.
cipants. Results of the logistic
regression show that the negative effect of the lottery on full portion choice was moderated
. There was a significant negative interaction between lottery and
.05), suggesting that the negative effect of the lottery on full
cognitively
, the more likely that an increasing lottery ticket amount leads to
REWARD SUBSTITUTION

MODERATES THE
Note.—The variable “lotteryxco

Behavioral inhibition and behavioral activation
argues that two generic motivational systems underlie behavior:
system (BIS) and a behavioral activation system (BAS)
referred to as behavioral approach system
BIS is an aversive motivational system that is sensitive to punishment, non
novelty, the BAS is a appetitive motivational system
punishment, and escape from punishment
Both the BIS and the BAS
Carver and White (1994). First, participants
of this section of the questionnaire is a statement that a person may either agree with or
disagree with. For each item, indicate how much you agree or disagree with what the item
says. Please respond to all the items; do not lea
each statement. Please be as accurate and honest as you can be. Respond to each item as if
REWARD SUBSTITUTION
TABLE 23
COGNITIVE INSTABILITY
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxco~b” refers to the interaction term.
Behavioral inhibition and behavioral activation. Extensive research on motivation
argues that two generic motivational systems underlie behavior: a behavioral inhibition
system (BIS) and a behavioral activation system (BAS). The latter is sometimes also
referred to as behavioral approach system (Carver & White, 1994; Gray, 1981)
BIS is an aversive motivational system that is sensitive to punishment, non-reward, and
etitive motivational system that is sensitive to reward, non
punishment, and escape from punishment (Carver & White, 1994).
the BAS were examined using a 24-item scale developed
. First, participants received the following instructions
of this section of the questionnaire is a statement that a person may either agree with or
disagree with. For each item, indicate how much you agree or disagree with what the item
says. Please respond to all the items; do not leave any blank. Choose only one response to
each statement. Please be as accurate and honest as you can be. Respond to each item as if
64

Extensive research on motivation
behavioral inhibition
sometimes also
(Carver & White, 1994; Gray, 1981). While the
reward, and
is sensitive to reward, non-
developed by
instructions: “Each item
of this section of the questionnaire is a statement that a person may either agree with or
disagree with. For each item, indicate how much you agree or disagree with what the item
ve any blank. Choose only one response to
each statement. Please be as accurate and honest as you can be. Respond to each item as if
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65
it were the only item. That is, don't worry about being "consistent" in your responses.”
Next, participants rated the following 24 items on a four-point Likert-type scale from 1
(“very true for me”) to 4 (“very false for me”). Items were: (1) “A person’s family is the
most important thing in life,” (2) “Even if something bad is about to happen to me, I rarely
experience fear or nervousness,” (3) “I go out of my way to get things I want,” (4) “When
I'm doing well at something I love to keep at it,” (5) “I’m always willing to try something
new if I think it will be fun,” (6) “How I dress is important to me,” (7) “When I get
something I want, I feel excited and energized,” (8) “Criticism or scolding hurts me quite a
bit,” (9) “When I want something I usually go all-out to get it,” (10) “I will often do things
for no other reason than that they might be fun,” (11) “It’s hard for me to find the time to
do things such as get a haircut,” (12) “If I see a chance to get something I want I move on it
right away,” (13) “I feel pretty worried or upset when I think or know somebody is angry at
me,” (14) “When I see an opportunity for something I like I get excited right away,” (15) “I
often act on the spur of the moment,” (16) “If I think something unpleasant is going to
happen I usually get pretty ‘worked up’,” (17) “I often wonder why people act the way they
do,” (18) “When good things happen to me, it affects me strongly,” (19) “I feel worried
when I think I have done poorly at something important,” (20) “I crave excitement and new
sensations,” (21) “When I go after something I use a ‘no holds barred’ approach, (22) “I
have very few fears compared to my friends,” (23) “It would excite me to win a contest,”
and (24) “I worry about making mistakes.” Items were averaged for each participant.
Carver and White (1994) identified four different factors: BIS, BAS reward responsiveness,
BAS drive, and BAS fun seeking.
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BIS. The “BIS” factor
(24). Averaged data were available
regression show that the negative effect of the lottery on full portion choice was moderated
by the BIS. There was a significant positive interaction bet
.05), suggesting that the negative effect of the lottery on full portion choice was alleviated
by the BIS. In other words, more
an increasing lottery ticket amount leads to fewer full portion choices
BIS MODERATES THE
Note.—The variable “lotteryxbis

BAS reward responsiveness
measured by items (4), (7), (14), (18), and (23).
participants. Results of the logistic regression show that the negative effect of the lottery on
full portion choice was not moderated by
significant negative interaction between lottery and
REWARD SUBSTITUTION
factor was measured by items (2), (8), (13), (16), (19), (22), and
Averaged data were available from all 217 participants. Results of the logistic
regression show that the negative effect of the lottery on full portion choice was moderated
. There was a significant positive interaction between lottery and the
), suggesting that the negative effect of the lottery on full portion choice was alleviated
. In other words, more behaviorally inhibited participants are, the less likely that
an increasing lottery ticket amount leads to fewer full portion choices (Table 24
TABLE 24
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxbis” refers to the interaction term.
BAS reward responsiveness. The factor “BAS reward responsiveness” was
measured by items (4), (7), (14), (18), and (23). Averaged data were available
participants. Results of the logistic regression show that the negative effect of the lottery on
moderated by reward responsiveness. Table 25 shows
significant negative interaction between lottery and reward responsiveness (p > .0
66
(19), (22), and
from all 217 participants. Results of the logistic
regression show that the negative effect of the lottery on full portion choice was moderated
the BIS (p <
), suggesting that the negative effect of the lottery on full portion choice was alleviated
, the less likely that
24).
EFFECT

. The factor “BAS reward responsiveness” was
from all 217
participants. Results of the logistic regression show that the negative effect of the lottery on
Table 25 shows no
> .02).
REWARD SUBSTITUTION

BAS REWARD RESPONSIV
MODERATE
Note.—The variable “lotteryxba

BAS drive. The “BAS drive”
Averaged data were available
show that the negative effect of the lottery on full portion choice was moderated by
drive factor of the BAS. There was a significant negative interaction between lottery and
BAS drive (p < .01), suggesting that the negative effect of the lottery on full portion choice
was intensified by BAS drive. In other words, the more
likely that an increasing lottery ticket amount leads to fewer full portion choices
REWARD SUBSTITUTION
TABLE 25
BAS REWARD RESPONSIVENESS DOES NOT
MODERATE THE REWARD SUBSTITUTION EFFECT
“lotteryxba~d” refers to the interaction term.
. The “BAS drive” factor was measured by items (3), (9), (12), and (21).
Averaged data were available from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by
. There was a significant negative interaction between lottery and
), suggesting that the negative effect of the lottery on full portion choice
. In other words, the more “drive” participants have
likely that an increasing lottery ticket amount leads to fewer full portion choices
67

was measured by items (3), (9), (12), and (21).
from all 217 participants. Results of the logistic regression
show that the negative effect of the lottery on full portion choice was moderated by the
. There was a significant negative interaction between lottery and
), suggesting that the negative effect of the lottery on full portion choice
“drive” participants have, the more
likely that an increasing lottery ticket amount leads to fewer full portion choices (Table 26).
REWARD SUBSTITUTION

BAS DRIVE MODERATES THE
Note.—The variable “lotteryxba

BAS fun seeking. The “BAS fun seeking”
(15), and (20). Results of the logistic regression showed that the likelihood of choosing the
half food portion is 0.8 times smaller for
are more fun-seeking (z = 5.2,
participants. Results of the logistic regression show that the negative effect of the lottery on
full portion choice is not moderated by
interaction between lottery and
REWARD SUBSTITUTION
TABLE 26
MODERATES THE REWARD SUBSTITUTION EFFECT
“lotteryxba~e” refers to the interaction term.
. The “BAS fun seeking” factor was measured by items (5), (10),
the logistic regression showed that the likelihood of choosing the
times smaller for less fun-seeking participants than for those that
, p < .001). Averaged data were available from all 217
s. Results of the logistic regression show that the negative effect of the lottery on
full portion choice is not moderated by BAS fun-seeking. Table 27 shows no significant
interaction between lottery and BAS fun seeking (p > .2).
68
EFFECT

was measured by items (5), (10),
the logistic regression showed that the likelihood of choosing the
than for those that
from all 217
s. Results of the logistic regression show that the negative effect of the lottery on
no significant
REWARD SUBSTITUTION

BAS FUN
THE REWARD SUBSTITUTION
Note.—The variable “lotteryxba

3.4. Discussion

Study 1 provides initial behavioral
Consumers switched from choosing the full portion without a non
half portion was offered with such a reinforcer. Results show that the mean choice
percentage of choosing the half portion increases significantly with increa
amount (from $10 to $50) but not beyond (from $50 to $100), suggesting that restaurants
do not have to offer exorbitant lottery amounts to incentivize consumers to choose the
smaller portion.
Besides uncovering the direct effect of
choice, another goal of Study
effect and to put it into perspective regarding
As such, besides the behavioral task,
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TABLE 27
FUN SEEKING DOES NOT MODERATE
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“lotteryxba~n” refers to the interaction term.
initial behavioral evidence for the reward substitution
Consumers switched from choosing the full portion without a non-food reinforcer once the
half portion was offered with such a reinforcer. Results show that the mean choice
percentage of choosing the half portion increases significantly with increasing lottery
amount (from $10 to $50) but not beyond (from $50 to $100), suggesting that restaurants
do not have to offer exorbitant lottery amounts to incentivize consumers to choose the
Besides uncovering the direct effect of reward substitution on consumers’ food
Study 1 was to investigate the robustness of the reward substitution
into perspective regarding possible moderating or nullifying
besides the behavioral task, a large-scale survey was conducted among
69

reward substitution effect:
food reinforcer once the
half portion was offered with such a reinforcer. Results show that the mean choice
sing lottery
amount (from $10 to $50) but not beyond (from $50 to $100), suggesting that restaurants
do not have to offer exorbitant lottery amounts to incentivize consumers to choose the
on consumers’ food
reward substitution
or nullifying variables.
among
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70
participants in Study 1 to determine whether their age, gender, body mass index, satiety,
preferences, emotional well-being, trait impulsivity, and behavioral inhibition/activation
affect the reward substitution effect. As a result, Study 1 offers compelling evidence that
the reward substitution effect is robust against powerful motivational conditions such as
hunger. Despite hypothesizing that these conditions could represent strong boundary
conditions, neither hunger nor body mass index nullified the reward substitution effect.
Instead, results show that body mass index alleviates the negative effect of the lottery on
full portion choice but does not cancel out this effect. Furthermore, hunger (measured as
self-perceived satiety) did not moderate the reward substitution effect.
Study 1 provides further insights into the moderating impact of these variables.
First, Study 1 shows that consumer preference indeed matters for the effectiveness of the
reward substitution effect. Consumer preference for foods being healthy and helping with
weight-control intensified the negative effect of the lottery on full portion choice; in other
words, if consumers are health- and weight-conscious, the effectiveness of reward
substitution increases. On the contrary, for those that prefer foods that lead to good mood,
are inexpensive, and are familiar, the negative effect of the lottery on full portion choice is
alleviated; in other words, if consumers prefer well-known “feel-good” foods, the
effectiveness of reward substitution decreases.
Study 1 showed that the reward substitution effect is dependent on consumers’
emotional well-being. In particular, for consumers’ experiencing both positive affect and/or
satisfaction with their lives, the effectiveness of reward substitution increased. However,
for consumers’ experiencing negative affect, the effectiveness of reward substitution
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71
decreased. This suggests that the monetary lottery symbolizes a more effective incentive
stimulus for choosing less food for those participants that feel positively and are happy with
themselves, but less so for those consumers that feel negatively. This finding may imply
that consumers experiencing negative effect resort to larger portions to get rewarded, more
so than playing the lottery and eating less.
Furthermore, trait impulsivity exerted a profound impact on the reward substitution
effect: While the effectiveness of reward substitution increased for participants that
exhibited greater cognitive instability, it decreased for participants that exhibited greater
overall impulsivity, motor impulsiveness, self-control, cognitive complexity, and
perseverance. It would be interesting to explore further why impulsivity and self-control
both decreased the effectiveness of reward substitution. Why did participants who scored
higher on impulsivity choose the full portion more often and not the lottery? Did those
participants who scored higher on self-control chose the larger meal in order prevent
themselves from gambling? While this research does not answer these questions, it
provides implications for future studies to investigate trait impulsivity and their influence
on reward substitution.
Finally, the moderating impact of both the behavioral inhibition system (BIS) and
the “drive” factor of the behavioral activation system (BAS) raise additional questions.
Both variables increased the effectiveness of reward substitution. Did the inhibition refer to
an inhibition to choose the larger meal, while the “drive” activation referred to an urge to
choose the lottery? Again, the design of this research does not allow for satisfactorily
answering these important questions but provides opportunities for future research.
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72
Despite the fact that Study 1 provided convincing initial evidence for reward
substitution and its effectiveness to lower food portion size, Study 2 was conducted for two
imperative reasons. First, Study 2 was set-up to be run in the lab and replicate the
behavioral effect of Study 1, which was run in a more uncontrolled field setting over the
Internet. Second, Study 1 did not shed light on the underlying psychological and
physiological processes. For this reason, Study 2 was conducted while participants were
undergoing functional magnetic resonance imaging, which allowed for investigating the
underlying neurophysiological mechanisms associated with choosing the half-sized meal
with the non-food reinforcer compared to choosing regular full-sized meals without such
non-food reinforcers. The hypothesis was that the combination of a small food portion and
a non-food reinforcer would add up in terms of striatal activation (or, indirectly,
mesolimbic dopamine) to the striatal activation of a large food portion alone. This account
builds on the notion of a common dopamine currency (Montague & Berns, 2002; Schultz,
et al., 1997; Wise, 1978), but also adds to previous research. While extant work has
investigated overlapping activation in the mesolimbic dopamine system for food and
money (Kim, et al., 2011), it has not extended this idea to smaller food portion choice. In
Study 2, overlapping activation in the striatum is expected to explain the link between
portion size/lottery ticket on portion choice.

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Chapter 4. Study 2: The Underlying Neurophysiological Mechanisms
of the Reward Substitution Effect

4.1. Introduction

Besides replicating the behavioral results from Study 1, the main aim of Study 2
is to test hypotheses H2a and H2b, which state that (1) a combination of a small food
portion and a non-food reinforcer adds up in terms of striatal activation (or, indirectly,
mesolimbic dopamine) to the striatal activation of a large food portion alone, which
becomes evident in overlapping activation in the striatum, and (2) that this effect extends to
choice. These hypotheses build on contemporary neuroimaging research, which find that
the striatum is involved when wanting incentive-salient stimuli, including food (Berridge,
1996, 2009), money (Kim, et al., 2011; Knutson, et al., 2001; Valentin & O'Doherty, 2009),
beautiful faces (Aharon, et al., 2001), preferred products (Knutson, et al., 2007), and
aesthetic products (Reimann, et al., 2010).
Based on this evidence, blood oxygen level dependent (or BOLD) responses in the
striatum prior to choosing full food portions without a non-food reinforcer are expected to
significantly “overlap” with brain activation prior to choosing half portions with such a
reinforcer. Figure 14 provides the overview of Chapter 4.
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THESIS OVERVIEW: CHA

4.2. Method

Sample. A sample of 45
psychology subject pool of the
informed consent to the protocol of the university’s Institutional Review Board,
checked for medical eligibility to participate in a functio
study. They engaged in a binary food choice task while undergoing
Dornsife Neuroimaging Center
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FIGURE 14
THESIS OVERVIEW: CHAPTER 4
45 adult individuals was obtained from the campus and the
the University of Southern California. Participants
informed consent to the protocol of the university’s Institutional Review Board,
checked for medical eligibility to participate in a functional magnetic resonance imaging
in a binary food choice task while undergoing neuroimaging
Dornsife Neuroimaging Center at the University of Southern California and received $20
74

campus and the
. Participants gave written
informed consent to the protocol of the university’s Institutional Review Board, were
nal magnetic resonance imaging
neuroimaging at the
and received $20
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75
and course credit for their participation. Similar to Study 1, participants were offered binary
choices between full-portion meals without a lottery ticket and half-portion meals with a
lottery ticket in a within-subjects, repeated-measures experiment. Once the data collection
was completed, the first participant was removed from the dataset, since this participant
helped test the validity of the behavioral task within the scanner, after which a few
adjustments were made to the task and scanner timing. In accordance with Study 1’s
procedures, individuals who did not sufficiently respond to the behavioral task were
excluded from further analyses. Specifically, participants who did not make choices in the
repeated-measures experiment in all choice categories (i.e., full portion choice, half portion
choice with $0 lottery ticket, half portion choice with $10 lottery ticket, half portion choice
with $50 lottery ticket, and half portion choice with $100 lottery ticket) were excluded. The
filtering resulted in a valid dataset of n = 23 (57% female; M
age
= 22 years).
Stimuli. The same stimuli were used as for Study 1. As described in more detail in
Study 1, food pictures were taken at typical American fast food restaurant chains (e.g.,
McDonald’s, Burger King, Taco Bell) before a neutral background and included adult-
sized portions of standard fast food meals, including Big Mac, Burrito Supreme,
Quesadilla, Cheeseburger, Chicken Sandwich, Hot Dog, Chicken Taco, Hamburger, Pizza,
Whopper, Footlong Sandwich, and Special Hot Dog.
Experimental task. The experimental task was designed in E-Prime 2.0 (E-Studio
Professional, version 2.0.8.22, manufactured by Psychological Software Tools, Inc.,
Sharpsburg, Pennsylvania), which allowed for recording of the behavioral button presses
on a four-button response box. Similar to the approach in Study 1, participants were
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76
instructed to press the “1” button on the far left for the “1” choices (i.e., full portion
choices) and the “2” button on the response box for the “2” choices (i.e., half portion
choices).
Scanning procedure. Before the fMRI experiment, participants were guided to a
preparation room where they gave written informed consent and were checked for
neuroimaging eligibility. They were asked to answer several different questions survey
displayed on a computer; the survey was administered through the Qualtrics account of the
University of Southern California. Participants reported liking and occasionally eating the
foods presented to them during the experiment. After answering the survey items,
participants were guided to the fMRI scanner room, engaged in a short training version of
the FOOD task, and asked to place all loose, metallic objects into a locker before lying
down supine on a stretcher.
Once inside the brain scanner, participants were shown the following instructions.
All visual stimuli were presented through the E-Prime 2.0 software and projected onto a
mirror directly in front of participants. They received the following instructions: “In the
following task, you will be offered foods from well-known restaurant chains. You will
always make your choice between two options. One of the two options will include only a
food item, the other option will include a food item and sometimes the opportunity of a
lottery participation. After being presented with the food options for a few seconds, you will
be prompted to choose one of the two options by pressing "1" for Option 1 OR by pressing
"2" for Option 2. The price of the two options is equal: Option 1 is always $4 and Option 2
is always $4, too. Over the course of the task, each food will be presented 4 times. After the
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task, you will receive a coupon for the two foods you chose most often.
$4) from your earnings today.
foods you will actually receive is
participate in that lottery. I will then notify you about your winnings after the drawings in a
few weeks. Remember: First, look at the two options. Then, choose one option by pressing
1 OR 2. < The FOOD TASK will start now >.
the instructions of the E-Prime task.
EXEMPLARY VIEW

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task, you will receive a coupon for the two foods you chose most often. I will deduct $8 (2 x
$4) from your earnings today. Thus, your choices are REAL! The maximum number of
foods you will actually receive is 2. If you chose a food together with a lottery, you will also
will then notify you about your winnings after the drawings in a
few weeks. Remember: First, look at the two options. Then, choose one option by pressing
< The FOOD TASK will start now >.” Figure 15 illustrates how participants saw
Prime task.
FIGURE 15
EXEMPLARY VIEW OF E-PRIME TASK
77
will deduct $8 (2 x
The maximum number of
If you chose a food together with a lottery, you will also
will then notify you about your winnings after the drawings in a
few weeks. Remember: First, look at the two options. Then, choose one option by pressing
illustrates how participants saw

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78

As in Study 1, participants were intentionally left in uncertainty by not disclosing
winning probabilities for the lottery, which was crucial for the experiment to mirror reality.
This also prevented participants from engaging in any winning probability calculations.
The experiment was incentive compatible, following Study 1.
Once the choice task started, participants were shown photos of the full and the half
portion of 12 different foods in pseudo-randomized order. During this six-second pre-
decision phase, participants considered the two different options and anticipated their
subsequent choice. Next, participants were prompted to choose one of the two options from
the message “Choose One,” which was displayed for four seconds (choice phase), followed
by a two-second confirmation of their choice (confirmation phase). Finally, participants
saw a white cross for two seconds to maintain their attention before the next trial started
(fixation phase). Figure 16 illustrates the trial structure and timing of the E-Prime-version
of the FOOD task. One of 48 trials (equal to 12 different foods x 4 different lottery ticket
amounts) is shown. Specifically, the figure shows the trial with a Big Mac and a $10 lottery
ticket.
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TRIAL STRUCTURE AND
After the scanning session
monetary reimbursement. The money
deducted from their reimbursement.
collection resulted in a usable sample of n =
FMRI data collection.
conducted using a full-body 3.0 Tesla Magnetom scanner (
Erlangen, Germany) fitted with a 12
was run, followed by the shimming sequence and the functional scan.
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FIGURE 16
TRIAL STRUCTURE AND TIMING OF EXPERIMENTAL TASK
IN THE FMRI STUDY
session, participants collected their belongings and received
he money that they paid for their food choices was not
from their reimbursement. Participants also received course credit. The data
collection resulted in a usable sample of n = 23 with complete responses.
ollection. Functional magnetic resonance imaging (fMRI)
body 3.0 Tesla Magnetom scanner (manufactured by Siemens,
tted with a 12-channel matrix head coil. First, a short localizer scan
the shimming sequence and the functional scan.
79
AL TASK

and received
was not
The data
Functional magnetic resonance imaging (fMRI) was
Siemens,
First, a short localizer scan
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80
For functional imaging, a time series of 261 volumes with 41 slices in the
transverse plane was obtained using single shot gradient-echo planar imaging (repetition
time (TR) = 2,000ms, echo time (TE) = 25ms, flip angle = 90°, resolution = 3.0mm x
3.0mm x 2.5mm, and FOV = 192mm). For structural imaging, a high-resolution image of
the brain was acquired with a 3D T1-weighted MPRAGE sequence (echo time (TE) /
repetition time (TR) / inversion time = 3.1 / 2,530 / 800ms, flip angle = 10°, matrix = 256 x
256, field of view (FOV) = 256mm, slice thickness = 1mm without gap).
FMRI data analyses. Imaging data were preprocessed and analyzed using
BrainVoyager QX 2.20 (Goebel, Esposito, & Formisano, 2006). For each participant, linear
image realignment, co-registration, piecewise linear normalization to stereotactic
anatomical space (Talairach & Tournoux, 1988), slice-scan time correction, motion
correction, spatial smoothing with a three-dimensional Gaussian kernel, 4mm full-width at
half maximum, and temporal high-pass filtering were performed. Changes in the BOLD
response were assessed for each voxel using the volume map (i.e., the map of brain
function over the course of the experiment) of each subject.
First, for each subject, individual time course protocols were created, defining each
volume of the task. The dataset was then subdivided into ten two-second intervals, starting
at the onset of each trial. For each two-second interval, eight unique predictors were
created: (1) the instructions of the task (“Front”), (2) the pre-decision phase of choosing the
full portion when the half portion was paired with a $0 lottery (“FullChoice_Half$0”), (3)
the pre-decision phase of choosing the full portion when the half portion was paired with a
$10 lottery (“FullChoice_Half$10”), (4) the pre-decision phase of choosing the half portion
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81
when the half portion was paired with a $10 lottery (“HalfChoice_Half$10”), (5) the pre-
decision phase of choosing the half portion when the half portion was paired with a $50
lottery (“HalfChoice_Half$50”), (6) the pre-decision phase of choosing the half portion
when the half portion was paired with a $100 lottery (“HalfChoice_Half$100”), (7) the
actual choice phase (“Choice”), and (8) the confirmation phase (“Confirmation”). This
procedure resulted in a total of 80 predictors (equal to 10 two-second time intervals x 8
task-specific predictors). The onset of each predictor was convolved with a finite impulse
response function (FIRF) and modeled to identify voxels with blood flow that correlated
with the predictors, resulting in a single-design matrix for each subject. This FIRF
approach makes no assumptions about the specific details of the hemodynamic response
function (HRF). It is significantly more sensitive than the HRF approach and particularly
suitable for event-related fMRI (Glover, 1999).
Next, a multi-subject-design matrix was created, which included all 23 single-
subject design matrices, and data were submitted to a random-effects, z-transformed,
deconvoluted general linear model (GLM) with motion predictor. In line with previous
decision neuroscience research finding that the brain responds in anticipation of a
subsequent choice (Bechara, 2005; Bechara, Damasio, Tranel, & Damasio, 1997; Ernst &
Paulus, 2005; Knutson & Greer, 2008), the analyses focused on the comparison of the six-
second pre-decision phases leading up to one of four specific choices:
• (1) the pre-decision phase before making a full portion choice when the half
portion is paired with $0 lottery ticket (“FullChoice_Half$0”);
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82
• (2) the pre-decision phase before making a half portion choice when the half
portion is paired with $10 lottery ticket (“HalfChoice_Half$10”);
• (3) the pre-decision phase before making a half portion choice when the half
portion is paired with $50 lottery ticket (“HalfChoice_Half$50”); and
• (4) the pre-decision phase before making a half portion choice when the half
portion is paired with $100 lottery ticket (“HalfChoice_Half$100”).
Note that the data were sorted according to each participant’s actual choice. As
such, it can be assumed that the identified changes in the BOLD responses preceded and
possibly triggered the subsequent behavioral choice. Because the pre-decision phase
spanned a total of six seconds, contrasts were ran for the first, second, and third two-second
intervals (D0, D1, and D2, respectively) of the pre-decision phase for the aforementioned
four predictors to determine any differences in the BOLD responses between the two-
second intervals.
This resulted in twelve specific contrasts (equal to 4 conditions x 3 time intervals).
These contrasts were ran against the baseline condition, which BrainVoyager automatically
models based on all volumes of the run by subtracting the effect of all model predictors
(Goebel, 2010). Conceptually speaking, the decision to run the contrasts against the
baseline condition is reasonable to examine the BOLD response changes for each specific
condition. As such, conditions were not compared directly but rather with baseline
condition. The global statistical threshold was p < .05, and the cluster threshold was four
continuous voxels, which represents a default setting in BrainVoyager when enabling the
cluster threshold.
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83
Finally, based on the notion of a common reward currency, I was interested whether
there was a significant “overlap” (Kim, et al., 2011), in BOLD responses between the four
experimental conditions (i.e., overlapping BOLD activation between “FullChoice_Half$0,”
“HalfChoice_Half$10,” “HalfChoice_Half$50,” and “HalfChoice_Half$100.” In order to
analyze the overlapping BOLD responses between the four conditions, I created three
probabilistic maps for each of the three time intervals (i.e., one for D0, one for D1, and one
for D2). Once these probabilistic maps were created, I converted the voxel clusters to
volumes of interest in BrainVoyager. A small-cluster-suppression threshold of 300 was
applied, which represents a default setting in BrainVoyager. Subsequently, the peak
activation voxels of each volume of interests were summarized in a table, resulting in a
total of three tables for each of the three different time intervals. Each table was then used
as an input file in the Talairach client (Lancaster et al., 2000), and the nearest gray matter
was looked up for each peak activation voxel (Tables 28, 29, and 30 summarize these
results below).

4.3. Results

Behavioral results. Replicating the reward substitution effect that was identified in
Study 1, participants in Study 2 also chose the full portion most often when the half
portions were offered without a lottery ticket (mean (M) choice percentage of full portion =
.73), but less frequently when the half portions were paired with either a $10 ticket (M =
.35), $50 ticket (M = .09), or $100 ticket (M = .07). Specifically, the mean choice
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84
percentage of full portions was significantly lower when half portions were paired with a
$10 ticket than when no ticket was offered (t(22) = 5.82, p = .001, paired samples, effect
size r = .78). The mean choice percentage of full portions dropped significantly when the
half portions were offered with a $50 ticket compared to $10 (t(22) = 4.48, p = .001, paired
samples, effect size r = .69) but not between $100 and $50 (p > .1).
Figure 17 illustrates the behavioral results of Study 2. This figure shows a
replicated pattern of results from Study 1: First, a significant drop in the percentage of full
portion choice is shown once the $10 lottery ticket is introduced with the half portion.
Second, increasing the lottery ticket amount from $10 to $50 results in a further significant
decrease in the percentage of full portion choice. Third, as shown in Study 1 and replicated
in Study 2, further increasing the lottery ticket amount from $50 to $100 did not result in an
additional significant decrease in the percentage of full portion choice. This implies that the
optimal lottery ticket amount in terms of decreased full portion choice percentage is
somewhere between $10 and $50.
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STUDY 2: PERCENTAGE
INCREASING LOTTERY A
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FIGURE 17
STUDY 2: PERCENTAGE OF FULL PORTION CHOICE DECREASES WITH
INCREASING LOTTERY AMOUNT
85
CE DECREASES WITH

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Neuroimaging results.
activation in the dorsal parts of the striatum
and caudate tail, during the first two time intervals (
i.e., after participants were confronted with the incentive
made their choices. Figure 18 shows a significant increase in BOLD response in the
striatum (here, caudate head) compared to the baseline condition during the
interval. The figure shows three
and coronal .
SIGNIFICANT INCREASE IN BOLD RESPONSE IN THE
Note.—Increased activation in the
between six and four seconds (interval “
portion was paired with a $50 lottery ticket. The Talairach coordinate
marked with crosshairs.

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. Results of the neuroimaging study show increased BOLD
dorsal parts of the striatum, specifically the caudate head, caudate
, during the first two time intervals (D0 and D1) of the pre-decision phase,
participants were confronted with the incentive-salient stimuli and before
their choices. Figure 18 shows a significant increase in BOLD response in the
striatum (here, caudate head) compared to the baseline condition during the D0
nterval. The figure shows three views of the brain (from left to right): saggital, traverse ,
FIGURE 18
SIGNIFICANT INCREASE IN BOLD RESPONSE IN THE DORSAL STRIATUM
COMPARED TO BASELINE
Increased activation in the dorsal striatum is shown for the “pre-decision phase”
between six and four seconds (interval “D0”) before making half portion choice when half
portion was paired with a $50 lottery ticket. The Talairach coordinates of -18, 19, 9 were
86
increased BOLD
caudate body,
decision phase,
before they
their choices. Figure 18 shows a significant increase in BOLD response in the dorsal
D0 time
saggital, traverse ,
STRIATUM

decision phase”
”) before making half portion choice when half
18, 19, 9 were
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Besides differences in the BOLD responses during the time interval “
identified differences are also identified
decision phase.” As Figure 19 shows, a
striatum (here, caudate body) compared to the baseline condition during the time interval
“D0” occurs prior to making choices
SIGNIFICANT INCREASE IN BOLD RESPONSE IN THE
Note.—Increased activation in the caudate
between four and two seconds (interval “
portion was paired with a $0 lottery ticket. The Talairach coordinate
marked with crosshairs.

More importantly, results also revealed overlapping
striatum—in the caudate head, body, and tail
the four different experimental conditions “
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erences in the BOLD responses during the time interval “D0
are also identified during the D1 time interval “D1” of the “pre
decision phase.” As Figure 19 shows, another significant increase in BOLD response in the
) compared to the baseline condition during the time interval
occurs prior to making choices.
FIGURE 19
SIGNIFICANT INCREASE IN BOLD RESPONSE IN THE DORSAL STRIATUM
COMPARED TO BASELINE
Increased activation in the caudate body is shown for the “pre-decision phase”
between four and two seconds (interval “D1”) before making full portion choice when half
portion was paired with a $0 lottery ticket. The Talairach coordinates of 23, -12, 30 were
ortantly, results also revealed overlapping BOLD responses in the
in the caudate head, body, and tail—when overlaying the activation from each of
experimental conditions “FullChoice_Half$0,” “HalfChoice_Half$10
87
D0,” I also
” of the “pre-
significant increase in BOLD response in the
) compared to the baseline condition during the time interval
STRIATUM

decision phase”
”) before making full portion choice when half
12, 30 were
BOLD responses in the dorsal
overlaying the activation from each of
HalfChoice_Half$10,”
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88
“HalfChoice_Half$50,” and “HalfChoice_Half$100.” As described in detail above, I
created three probabilistic maps for each of the three time intervals (i.e., one for D0, one for
D1, and one for D2). For each of these three time intervals, I summarized the peak
activation voxels of each volume of interests in Tables 28, 29, and 30. For the time interval
“D0” of the six-second “pre-decision” phase prior to participants’ actual choice, Table 28
shows the overlapping brain activation in the dorsal striatum at and around Talairach
coordinates of x: 20, y: -18, and z: 30 in the right hemisphere, x: 8, y: 23, and z: 0 in the
right hemisphere, and x: -18, y: 19, and z: 9 in the left hemisphere.
Next, for the time interval “D1” of the six-second “pre-decision” phase prior to
participants’ actual choice, Table 29 shows the overlapping brain activation in the dorsal
striatum at and around Talairach coordinates of x: 23, y: -12, and z: 30 in the right
hemisphere, x: -8, y: 1, and z: 21 in the left hemisphere, x: -19, y: -8, and z: 23 in the left
hemisphere, and x: -37, y: -38, and z: -3 in the left hemisphere.
Further, because no significant differences in BOLD responses at the striatal level
for the time interval “D2” of the six-second “pre-decision” phase prior to participants’
actual choice were identified during the whole-brain analyses, no overlap was found in the
probabilistic map for time interval “D2,” accordingly. Table 30 summarizes those brain
areas for which overlapping activation was identified during time interval “D2,” none of
which are at the striatal level.
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TABLE 28
OVERLAPPING BOLD RESPONSES IN FIRST TIME INTERVAL

Note.—An asterix (*) indicates that this category is not applicable.
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90
TABLE 29
OVERLAPPING BOLD RESPONSES IN SECOND TIME INTERVAL

Note.—An asterix (*) indicates that this category is not applicable.
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91
TABLE 30
OVERLAPPING BOLD RESPONSES IN THIRD TIME INTERVAL

Note.—An asterix (*) indicates that this category is not applicable.
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To further illustrate the overlapping BOLD responses between the four different
conditions, I created Figures 20 and 21. Figure 20 shows a significant overlap in BOLD
activation in the dorsal striatum, particularly the caudate head. The color bar indicates
percentage in overlapping activation
SIGNIFICANTLY OVERLAPPING BOLD RESPONSES
STRIATUM FOR THE FOUR EXPERIMENTAL CONDITIONS
Note.—Overlapping activation in the caudate head is shown for the “pre
between six and four seconds (interval “
“FullChoice_Half$0,” “HalfChoice_Half$10
“HalfChoice_Half$100.”. The Talairach coordinate
crosshairs.
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To further illustrate the overlapping BOLD responses between the four different
conditions, I created Figures 20 and 21. Figure 20 shows a significant overlap in BOLD
striatum, particularly the caudate head. The color bar indicates
ping activation.

FIGURE 20
SIGNIFICANTLY OVERLAPPING BOLD RESPONSES IN THE DORSAL
FOR THE FOUR EXPERIMENTAL CONDITIONS
Overlapping activation in the caudate head is shown for the “pre-decision phase”
and four seconds (interval “D0”) before the actual choice, between
HalfChoice_Half$10,” “HalfChoice_Half$50,” and
.”. The Talairach coordinates of -18, 19, 9 were marked with
92
To further illustrate the overlapping BOLD responses between the four different
conditions, I created Figures 20 and 21. Figure 20 shows a significant overlap in BOLD
striatum, particularly the caudate head. The color bar indicates the
THE DORSAL
FOR THE FOUR EXPERIMENTAL CONDITIONS

decision phase”
”) before the actual choice, between
18, 19, 9 were marked with
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Similarly, Figure 21 shows a significant overlap in BOLD activation in the
striatum, particularly the caudate body. Again, the color bar indicates the percent
overlap.
SIGNIFICANTLY OVERLAPPING
STRIATUM FOR THE FOUR EXPERIMENTAL CONDITIONS
Note.—Overlapping activation in the caudate body is shown for the “pre
between four and two seconds (interval “
“FullChoice_Half$0,” “HalfChoice_Half$10
“HalfChoice_Half$100.”. The Talairach coordinate
crosshairs.

On the basis of these results, this neuroimaging experiment provides ample
empirical support for hypotheses H2a and H2b. In particular, in hypothesis H2a, I predicted
that state that a combination of a small food portion and a non
terms of striatal activation (or, indirectly, mesolimbic dopamine) to the striatal activation of
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Similarly, Figure 21 shows a significant overlap in BOLD activation in the
striatum, particularly the caudate body. Again, the color bar indicates the percent
FIGURE 21
SIGNIFICANTLY OVERLAPPING BOLD RESPONSES IN THE DORSAL
FOR THE FOUR EXPERIMENTAL CONDITIONS
Overlapping activation in the caudate body is shown for the “pre-decision phase”
between four and two seconds (interval “D1”) before the actual choice, between
HalfChoice_Half$10,” “HalfChoice_Half$50,” and
.”. The Talairach coordinates of 23, -12, 30 were marked with
On the basis of these results, this neuroimaging experiment provides ample
empirical support for hypotheses H2a and H2b. In particular, in hypothesis H2a, I predicted
combination of a small food portion and a non-food reinforcer adds up i
terms of striatal activation (or, indirectly, mesolimbic dopamine) to the striatal activation of
93
Similarly, Figure 21 shows a significant overlap in BOLD activation in the dorsal
striatum, particularly the caudate body. Again, the color bar indicates the percent-wise
DORSAL
FOR THE FOUR EXPERIMENTAL CONDITIONS

decision phase”
between
12, 30 were marked with
On the basis of these results, this neuroimaging experiment provides ample
empirical support for hypotheses H2a and H2b. In particular, in hypothesis H2a, I predicted
food reinforcer adds up in
terms of striatal activation (or, indirectly, mesolimbic dopamine) to the striatal activation of
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a large food portion alone. Tables 28 and 29 as well as Figure 20 and 21 all show support
for this notion. Specifically, results suggest that overlapping BOLD activation in the
striatum occurs in the dorsal parts of this brain structure and during the first two time
intervals of the pre-decision phase (i.e., onset at second 0 and end at second 5) but not in
the last time interval of that same trial phase (i.e., onset at second 5 and end at second 7).
This latter finding suggests that the dopaminergic response happens relatively fast, after the
incentive-salient decision options are presented, and before the actual choice.
In summary, as predicted by hypothesis H2, whole-brain analyses showed that
increased activation in the dorsal striatum precedes not only the choice of full portions
when no ticket is offered with the half portion but also choices of half portions paired with
either a $10, $50, or $100 ticket. Importantly, an analysis of the extent of overlapping brain
activation between the four conditions illustrates significant overlap. Results show that
increased striatal activation preceding full-portion choices when no ticket is offered with
the half portion significantly overlaps with increased striatal activation preceding half-
portion choices when the winning amount of the ticket is either $10, $50, or $100.
Like most prior cognitive neuroscience research, the present functional magnetic
resonance imaging study relies on reverse inference in that activation of a particular brain
area (e.g., dorsal striatum) is interpreted as support for engagement of a particular
psychological process (e.g., reward). In dealing with this controversial issue, pertinent
recommendations (Poldrack, 2006) are closely followed. First, rather than pursuing an
exploratory approach that would rely on post-hoc explanation of a particular result, Study 2
was set up to test a very specific prediction pertaining to activation in the striatum that prior
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research has linked to the related concepts of reward, reinforcement, and incentive salience.
Second, I obtained an estimate for the degree to which the overlapping brain areas
identified in the present research are activated by “reward.” If selectivity was relatively
high, one can infer with greater confidence that reward are involved given activation in the
striatum. Using the neurosynth.org database (Yarkoni, et al., 2011), I found that activation
of the dorsal striatum, and revealed significant reverse inference z-scores for reward, which
means that taking brain activation into account makes an improvement to one’s prior
estimate of whether a reward process was involved. In particular, of the striatal regions
found in the present research, the brain regions at Talairach coordinatess of x: 8 (8), y: 23
(24), and z: 0 (0) as well as x: -18 (-16), y: 19 (20), and z: 9 (8), respectively, appeared to be
the most selective for processing reward (the numbers in brackets refer to the nearest
coordinates in the neurosynth.org database). These meta-analytic results indicate the two
regions as most appropriate regions of interest for my purposes (cf. Young & Saxe, 2009).
Table 31 summarizes the results of the meta-analysis and the aforementioned two brain
regions are highlighted in bold.
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TABLE 31
META-ANALYTIC RESULTS ON THE BASIS OF THE NEUROSYNTH.ORG DATABASE
(YARKONI, ET AL., 2011)
Brain area Functional processes implied
(keyword entered in
database)
Talairach coordinates of the region
of interest (nearest in database)

Reverse
inference z-
score
Posterior
probability
x

y z
Striatum

Reward

20 (20) -18 (-16) 30 (32) n/a n/a
Reward

8 (8) 23 (24) 0 (0) 6.37 .77
Reward

-18 (-16) 19 (20) 9 (8) 3.52 .69
Reward

23 (24) -12 (-12) 30 (32) n/a n/a
Reward

-8 (-8) 1 (0) 21 (20) 1.57 .62
Reward

-19 (-20) -8 (-8) 23 (24) .30 .56
Reward

-37 (-36) -38 (-36) -3 (-4) .24 .54
Note.—Brain areas were ordered as they appear in Tables 28 and 29. “n/a” stands for “not applicable” and refers to the fact
that no data was found for this location in the neurosynth.org database as of November 13, 2012 when the meta-analysis was
last conducted.
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Besides overlapping activation in the striatum, several other regions overlapped
significantly, as summarized in Tables 28, 29, and 30 as well as in Figures 20 and 21. For
example, I identified overlapping BOLD responses in the medial frontal lobe (particularly,
Brodmann area 10), the anterior and posterior cingulate cortex (particularly, Brodmann area’s
32 and 30), and the insula (particularly, Brodmann area 13). Further, overlapping activation
in the occipital lobe—the primary vision cortex (Clarke & Miklossy, 1990)—was found,
which supports the fact that participants engaged in visual perceptual activities when being
presented with the different food choice options.
Although I did not derive any a-priori hypotheses on these overlapping areas, the
extant literature provides some insight into the psychological functions that these areas may
subscribe to. These insights in turn offer opportunities for future research. As a word of
caution, however, I am entering speculative terrain here, by trying to conceptually link
possible psychological functions of these brain areas to the concept of reward substitution.
Such an approach bears a higher risk of reverse inference, as discussed above (Poldrack,
2006), especially because these brain areas ascribe to different and often unrelated
psychological functions.
Reward substitution and overlapping activation in the medial frontal lobe. The
overlapping activation in the prefrontal cortex for the different reinforcer types could be
explained by the role of the medial prefrontal cortex in processing judgments (Dubé et al.,
2008; Kober et al., 2010) and modulating self-control (Bechara, 2005; Bechara, Damasio,
Damasio, & Anderson, 1994; Bechara, Damasio, Damasio, & Lee, 1999; Bechara,
Damasio, Tranel, & Anderson, 1998; Bechara, et al., 1997; H. Damasio, Grabowski, Frank,
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Galaburda, & Damasio, 1994; Hare, Camerer, & Rangel, 2009; Tabibnia et al., 2011). This
effect may be rooted in increased dopaminergic projections to the prefrontal cortex,
because the ventral tegmental area projects not only to striatal areas but also to prefrontal
regions (Carr, O'Donnell, Card, & Sesack, 1999; Wise, 1978, 2002), leading to a
dopamine-induced disinhibition of this higher-order control region while processing these
self-regulatory judgments (Bechara, 2005).
Reward substitution and overlapping activation in the anterior cingulate cortex. The
anterior cingulate cortex is located on the medial surfaces of the brain’s frontal lobe and
includes subdivisions that are crucial for cognitive, motor, and emotional processing (Bush,
Luu, & Posner, 2000). The anterior cingulate cortex has also been associated with reward,
specifically reward-based decision making. Recent neuroimaging research differentiated cells
in the anterior cingulate cortex sensitive to reward-based decision making tasks from those
cells sensitive to reward reduction (Bush et al., 2002).
Overlapping activation in the posterior cingulate cortex. The posterior cingulate
cortex, located toward the back of the brain, has also been associated with reward and
reinforcement. For example, it has been correlated with the value of delayed rewards (Peters
& Buechel, 2009), action-based choice (Wunderlich, Rangel, & O'Doherty, 2009), and
responses to risks (Christopoulos, Tobler, Bossaerts, Dolan, & Schultz, 2009).
Reward substitution and overlapping activation in the insular cortex. Overlapping
activation was identified for the insular cortex, which is a translator of sensations that
arise in the body (Mesulam & Mufson, 1982a, 1982b). The insula has been proposed to
function in conscious urges through its role in the representation of bodily states, both
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negative states such as physical pain and addiction (ADB Craig, 2002, 2003a, 2003b; A.
R. Damasio, 1999) and positive ones such as love (Bartels & Zeki, 2000). For example,
researchers studying patients with insula damage found that the patients’ yearning for
smoking cigarettes was disrupted (Naqvi, Rudrauf, Damasio, & Bechara, 2007). In the
context of decision making, prior studies suggest that insular activation increases as
uncertainty increases (Huettel, Song, & McCarthy, 2005; Paulus, Rogalsky, Simmons,
Feinstein, & Stein, 2003; Preuschoff, Quartz, & Bossaerts, 2008). Taken together,
because participants were offered novel food options (i.e., half portions paired with a
lottery ticket), the insula may have processed the “fear of the unknown” (Camerer,
Loewenstein, & Prelec, 2004, p. 19), as it is a common substrate for feelings in the realm
of uncertainty (Singer, Critchley, & Preuschoff, 2009).
Reward substitution and overlapping activation in the temporal lobe. Decision
neuroscience studies have argued that areas of the temporal lobe exert a profound role in
emotional processing and decision making (Naqvi, Shiv, & Bechara, 2006), which may
explain overlapping activation in the decision making task (i.e., the FOOD task) used in the
present research.
Despite these important findings in extant decision neuroscience and their possible
conceptual relationship to the reward substitution concept, I would like to acknowledge that
these areas may also process other psychological functions that are conceptually unrelated to
reward substitution. As such, future research may further investigate the underlying
psychological functions of these brain areas in relationship to reward substitution in more
detail.
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4.4. Discussion
Study 2 replicates the behavioral part of the reward substitution effect within a
controlled lab setting. Study 2 provides convergent behavioral evidence that consumers
switched from choosing the full portion without a non-food reinforcer once the half portion
was offered with such a reinforcer. Results show that the mean choice percentage of
choosing the half portion increased significantly with increasing the lottery amount from
$10 to $50 but not from $50 to $100. This provides added support that restaurants do not
have to offer exorbitant lottery amounts to incentivize consumers to choose smaller
portions.
Study 2 was conducted while participants were undergoing neuroimaging,
allowing analyses of the underlying neurophysiological mechanisms associated with
choosing the half-sized meal with the non-food reinforcer compared to choosing regular
full-sized meals without such non-food reinforcers. As argued above in more detail, the
combination of a small food portion and a non-food reinforcer was hypothesized to add up
in terms of striatal activation to the striatal activation of a large food portion alone, building
on the idea of a common dopamine currency (Montague & Berns, 2002; Schultz, et al.,
1997; Wise, 1978). In support of hypotheses H2a and H2b, Study 2 found overlapping
activation in the striatum, particularly within the caudate, that explained the link between
portion size/lottery ticket on portion choice. Such overlapping striatal activation was found
after participants were offered the different food choice options and before they carried out
the behavioral act of choosing either a full portion or a half portion paired with either $10,
$50, or $100 in lottery tickets. In addition, another brain region of the mesolimbic
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dopamine system, the prefrontal cortex
what was found at striatal levels.
ventral tegmental area to the prefrontal cortex.
THE DOPAMINERGIC LIN
AND THE PREFRONTAL C
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the prefrontal cortex, exhibited overlap in BOLD responses
found at striatal levels. Figure 22 illustrates the projection of dopamine from the
ventral tegmental area to the prefrontal cortex.
FIGURE 22
THE DOPAMINERGIC LINK BETWEEN THE VENTRAL TEGMENTAL
AND THE PREFRONTAL CORTEX
101
exhibited overlap in BOLD responses similar to
Figure 22 illustrates the projection of dopamine from the
L TEGMENTAL AREA

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While some investigators have associated the prefrontal cortex with the concept of
reward valuation—that is, the cognitive assessment of the incentive-salient stimulus or
experience—(e.g., Chib, Rangel, Shimojo, & O'Doherty, 2009; Plassmann, O'Doherty, &
Rangel, 2007; Plassmann, O'Doherty, Shiv, & Rangel, 2008), an alternative explanation
could be that the induction of the neurotransmitter dopamine—a disinhibitor, per se—leads
to a disinhibition of the inhibiting (e.g., self-controlling or disciplining) function of the
prefrontal cortex (Bechara, 2005). As such, anticipating the choice of a food option
(independent of whether the food was a full or a half portion paired with a lottery ticket)
involves prefrontal structures to a similar extent as with striatal brain regions.
A prominent incident in medical history underscores the relationship between the
prefrontal cortex and self-control: the case of a nineteenth-century railroad worker,
Phineas Gage (see A. R. Damasio, 1994; H. Damasio, et al., 1994; Reimann & Zimbardo,
2011 for detailed descriptions of the case). Gage is best remembered for surviving an
accident in which an iron rod was driven through his head, damaging large sections of his
frontal lobe. After this accident, Gage’s physician noted dramatic changes in his
personality, social conduct, judgment, and decision making (Harlow, 1848, 1868). Gage
refused to show respect for social conventions, offended others with profanities, and
became uncontrolled and even aggressive in his behavior (Harlow, 1868).
While previous researchers investigating Gage’s case had to rely on Harlow’s
notes to draw conclusions, developments in technology have allowed recent researchers
to obtain evidence confirming that Gage’s uncontrolled behavior was linked to specific
frontal lobe damages. Using neuroimaging techniques to examine Gage’s preserved skull,
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investigators found that the lesion Gage experienced affected the prefrontal cortex (H.
Damasio, et al., 1994). Additionally, research in lesion patients as well as healthy
individuals undergoing neuroimaging has confirmed the relationship between frontal lobe
damage and self-control. Studies have shown that patients with prefrontal cortex lesions
can exhibit disinhibited behavior such as being socially inappropriate (e.g., E. Rolls,
Hornak, Wade, & McGrath, 1994). This evidence provides support to the notion that the
prefrontal cortex exerts a profound role in self-control when needed. When not needed—
for example, right before choosing an indulgent food option or anticipating a lottery
participating—the neurotransmitter dopamine disinhibits the proper functioning of this
executive control organ.

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Chapter 5

5.1. Introduction

This chapter presents the theoretical and empirical contribution
research. It also highlights limitations of this research, which in turn provide avenues for
future research, both behaviorally in nature and using neuroimaging technology. Finall
implications for practice and public policy
of this chapter.
THESIS OVERVIEW:
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Chapter 5. General Discussion
the theoretical and empirical contributions of the
limitations of this research, which in turn provide avenues for
future research, both behaviorally in nature and using neuroimaging technology. Finall
implications for practice and public policy are discussed. Figure 23 provides an overview
FIGURE 23
THESIS OVERVIEW: CHAPTER 5
104
of the present
limitations of this research, which in turn provide avenues for
future research, both behaviorally in nature and using neuroimaging technology. Finally,
an overview

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105
Taken together, this investigation provides convergent evidence that offering non-
food reinforcers bundled with smaller food portions as an alternative to full-portion meals
can substantially decrease chosen portion sizes (shown in both Study 1 and Study 2). This
effect is called “reward substitution,” that is, partially substituting a food reward with a
non-food reward in order to incentivize consumers to choose smaller portion. This effect
remains robust when considering the potential influences of hunger/satiety and body mass
index, which did not represent boundary conditions to the reward substitution effect. As
reported in Study 1, several important additional factors moderate the reward substitution
effect. These factors can be broadly categorized into preference-related factors and factors
related to emotional well-being, trait impulsivity, and behavioral activation/inhibition.
The results of the neuroimaging experiment (Study 2) show the position that BOLD
responses in the mesolimbic dopamine system prior to choosing full portions without a
non-food reinforcer significantly overlap with BOLD responses prior to choosing half
portions with such a reinforcer. Choosing a half-sized meal in combination with a non-food
reinforcer not only carries BOLD responses in the striatum similar to those when choosing
the full portion without such a reinforcer (evident in overlapping increased activation in the
dorsal striatum) but also similar overlapping BOLD responses in the prefrontal cortex
(evident in overlapping functional activation at several different medial prefrontal cortex
regions, including Brodmann area 10). These findings imply comparable increases in
dopamine in the dorsal striatum and thus similar levels of dopaminergic reward for both the
full-portion choices without non-food reinforcer and the half-portion choices with non-food
reinforcer.
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However, no increased overlapping activation was found in the ventral striatum,
which has previously been implicated in reward processing (e.g., Knutson, et al., 2001;
Knutson, et al., 2007). Previous neuroimaging studies show that much like the ventral
striatum (Balleine, Delgado, & Hikosaka, 2007), the dorsal striatum is also implicated in
both monetary (Koepp et al., 1998; Zald et al., 2004) and food rewards (O'Doherty,
Deichmann, Critchley, & Dolan, 2002; Volkow et al., 2002). This discrepancy suggests
that future studies should consider a more fine-grained analysis of the differential role of
the dorsal striatum and the ventral striatum in reward processing. At the same time, results
revealed comparable levels of overlapping activation in the prefrontal cortex, suggesting
that a dopamine surge may have resulted in a disinhibition of this higher-order control
region (Bechara, 2005). This result is in line with previous research on the case of Phineas
Gage and on lesion patients showing a lack of self-control (Bechara, et al., 1997; H.
Damasio, et al., 1994).
It is important to note that neuroimaging studies are not without problems when
inferring psychological function from brain activation, because these brain regions do not
possess very high levels of selectivity (see the discussion of reverse inference above).
While the highlighted Bayes factors reported in Table 31 (above) suggest a positive
increase in confidence that reward processes are involved, this increase is comparatively
fragile (Poldrack, 2006). As such, established knowledge from neuroscientific methods
other than neuroimaging—such as animal and lesion studies—are particularly helpful to
corroborate my account of reward valuation being engaged. I reviewed central parts of
these literatures throughout this thesis.
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5.2. Contributions

The present research makes contributions on several fronts. First, it provides
empirical evidence that attempts to promote the choice of smaller food portions can be
behaviorally effective, can involve similar levels of reward value at the striatal level, and
do not engage higher-order processing at prefrontal levels if non-food reinforcers are
offered as partial substitutes. Applying these findings in clinical intervention programs for
lowering food intake could have a significant impact for implementing healthier lifestyles.
Whereas many attempts to lower food intake fail because they require tapping into self-
regulatory resources which deplete over time (Vohs & Heatherton, 2000), the present effect
does not seem to depend on these resources. Furthermore, many weight loss programs
leave impulsive needs unsatisfied and can lead to backlash due to consumers’ difficulty to
resist temptations (Nordgren & Chou, 2011). The present approach provides a solution to
this dilemma by introducing non-food temptations (e.g., lottery, toy) that can provide
immediate reward.
Second, these findings have implications for motivational theories in psychology.
Most traditional theories on motivation depict a hierarchical structure of needs in the sense
that lower-order needs (e.g., food) must be satisfied before higher-order needs (e.g., play)
can arise (Kenrick, et al., 2010; Maslow, 1943). However, the current results provide
evidence that reinforcer interchangeability can work across need hierarchy levels,
supporting an alternative characterization of needs that has long been neglected (Alderfer,
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1969). As the present research shows, even hungry consumers may switch from larger to
smaller portions if the latter were paired with a non-food reinforcer.
Third, the present research also has important implications for economic theory.
The canonical economic model assumes that money is a simple counter and valued only for
the goods or services it can buy. Accordingly, the reward from food and the reward from
money are viewed as incommensurable—a perspective that has recently been criticized by
neuroeconomists (Camerer, et al., 2005). This research therefore contributes to
understanding the complicated issue of making seemingly incommensurable products
commensurable (Karpik, 2010). The present research highlights intrapersonal processes
that allow consumers to evaluate different types of products on a singular dimension, thus
establishing a personal preference order which represents the basis of cross-category choice
(Karpik, 2010). These findings provide relevant evidence that both monetary and non-
monetary reinforcers are not only processed similarly, suggesting that common utilities
exist at the brain level, but can also partially substitute each other.
Fourth, this research also speaks to somatic marker theory (Bechara & Damasio,
2005; A. R. Damasio, 1994, 1996; A. R. Damasio, Tranel, & Damasio, 1991). As
reviewed in detail elsewhere (Reimann & Bechara, 2010), somatic marker theory
provides the theoretical basis of the relationship between the ventromedial prefrontal
cortex and other brain areas, which include both brain stem structures (i.e., hypothalamus
and periaqueductal grey) and the amygdala. According to this theory, emotion-related
signals (i.e., somatic markers, which are sometimes also called bodily markers), which
are indexed changes in the visceral state (e.g., changes in heart rate, blood pressure, gut
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motility, and glandular secretion), interact with cognitive processes. These changes in the
visceral state can be considered as an expectation of the bodily impact of events in the
world that allows an organism to maximize the survival value of particular situations.
Somatic marker theory also proposes several neural structures that studies have
shown to be key components of the neural circuitry underlying somatic state activation.
Specifically, the amygdala and the ventromedial prefrontal cortex region (i.e., medial
frontal and orbitofrontal cortex) are vital structures for triggering somatic states. While
the amygdala seems to be more important for triggering somatic states from emotional
events that occur in the external environment, the ventromedial prefrontal cortex region
appears more vital for triggering somatic states from the internal cortical environment of
memories and knowledge (Bechara & Damasio, 2005; Reimann & Bechara, 2010).
Although not directly measured here, the motivation that comes from getting food or
playing the lottery arguably involves somatic states that interact with activation changes
at the brain level and impact downstream behaviors. The present research adds to somatic
marker theory by highlighting the dopaminergic link involved in food decision making
and specifically points out the dorsal striatum as an additional brain area to consider in
this neuroeconomic framework of decision making.

5.3. Limitations and Implications for Future Research

Clearly, this research has its methodological limitations, as already discussed. In
turn, these limitations provide avenues for future behavioral and neuroimaging research.
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First, research still needs to investigate the effect over longer time periods. While some
fallback to full portions may occur, frequently exchanging non-food reinforcers may keep
the offer of the smaller food portion exciting. Clues for making and keeping the non-food
reinforcers interesting for consumers are offered by marketing research on reward loyalty
programs (e.g., Bolton, Kannan, & Bramlett, 2000; Yi & Jeon, 2003). Additionally, prior
research on habitual consumption (Ji & Wood, 2007; W. Wood & Neal, 2009) and how to
break and change consumer habits (W. Wood & Neal, 2009) offer ideas for implementing
reward substitution in consumers’ daily food choices.
Second, the whole-brain analyses revealed activation in a number of other brain
areas, which should be explored in relationship to the concept of reward substitution.
Because a-priori hypotheses were not made about these brain areas, the interpretation of
these regions is limited. Future research could focus more specifically on these other
brain areas to investigate their neurophysiological role in processing reward substitution.
For example, additional research could manipulate the food reward delivery mode (e.g.,
immediate vs. delayed) to see whether the posterior cingulate is involved—an area that was
found to be active in the whole-brain analysis of the present research (Table 29) and which
has been linked to delayed reward valuation in extant research (e.g., Peters & Buechel, 2009).
Third, future research could hone the FOOD task to gain access to other brain
areas possibly related to reward and reinforcement but that were not identified in the
present analysis. For example, the ventral striatum (specifically, the nucleus accumbens),
is generally involved in the anticipation of reward; that is, an individual’s expectation
related to a positive object, behavior, or internal state (Knutson, et al., 2001).
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Fourth, three alternative process mechanisms have been suggested: mere
categorization, thrill-based uncertainty, and valuation. While future research will have to
test these potential mechanisms more systematically, the only “superior” mechanism
from a practical perspective is likely to be the lottery-based mechanism because
restaurants and food manufacturers would not have to pay out consumers every single
time or provide a more complex system of reward categories. More specifically, to test
for the possibility that the reward substitution effect is based on mere categorization,
future research could manipulate the number of categories offered, by comparing the
percentage of chosen full portion sizes when either two non-food reward categories (e.g.,
one lottery ticket and one card gamble, or one souvenir pen and one souvenir t-shirt) or
three non-food rewards are offered. Following the logic of the mere categorization effect
(Mogilner, et al., 2008), two additional non-food rewards (from two separate categories)
should lead to more pleasure than just one, and three should lead to more pleasure than
just two. Furthermore, to test for the possibility that the reward substitution effect is
based on the pleasure of the lottery’s uncertainty, future research could manipulate the
level of uncertainty by comparing the percentage of chosen full portion sizes when either
uncertain non-food rewards (e.g., lottery ticket, card gamble) or certain non-food rewards
(e.g., reward points similar to the airlines’ frequent travel miles) are offered.

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5.4. Practical Implementation and Public Policy Implications

This research also provides some practical implications and suggestions for public
policy making. First, the findings can help restaurants and food manufacturers to keep
smaller portion sizes and packages on their menus and shelves. Recently, restaurants and
producers have eliminated smaller portion sizes due to decreased demand (Sharpe, et al.,
2008). Introducing smaller food packages to the marketplace has been shown to be only
profitable for firms under very specific circumstances (Jain, 2012). This raises the question
of whether firms should actively offer such smaller packages and risk losing profitability.
Based on the present results, the answer is yes. Smaller portion options benefit consumers
by providing healthier alternatives, and restaurants are able to charge the same price for the
half portion if paired with a non-food reinforcer such as lottery tickets or reward points.
Second, this research suggests that public policy makers do not have to extend laws
and regulations drastically, for instance, prohibiting restaurants from selling high energy-
dense, large-portion meals as in San Francisco. The city stopped McDonalds from selling
Happy Meals (Bernstein, 2010), arguably a large portion for its target group of children.
However, a “reverse Happy Meal,” for example, using a toy (a non-food reinforcer) to sell
smaller portions, could help kids make better” food choices. Restaurants could offer a kids
meal with a toy and a smaller burger versus a kids meal with a regular, bigger burger but no
toy. I expect that children (and some adults) will choose the former.

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Asset Metadata

Creator Reimann, Martin (author)

Core Title Reward substitution: how consumers can be incentivized to choose smaller food portions

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Psychology

Publication Date 03/29/2015

Defense Date 02/25/2013

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag consumer neuroscience,fMRI,incentive saliance,mesolimbic dopamine system,neuromarketing,OAI-PMH Harvest,reward and positive reinforcement,smaller food portion choice,striatum,Wanting

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Bechara, Antoine (committee chair), Dawson, Michael Edward (committee member), MacInnis, Deborah J. (committee member), Monterosso, John (committee member), Wood, Wendy (committee member)

Creator Email mreimann@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-228495

Unique identifier UC11295185

Identifier usctheses-c3-228495 (legacy record id)

Legacy Identifier etd-ReimannMar-1493.pdf

Dmrecord 228495

Document Type Dissertation

Rights Reimann, Martin

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA