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Can infants discriminate between declaratives and interrogatives?

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Can infants discriminate between declaratives and interrogatives?

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Content CAN INFANTS DISCRIMINATE BETWEEN DECLARATIVES
AND INTERROGATIVES?

by
Susan Geffen
________________________________________________________________________

A Thesis Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF ARTS
(PSYCHOLOGY)

December 2010

Copyright 2010 Susan Geffen
ii

Table of Contents
List of Figures iii
Abstract iv
Background 1

Experiment 1: Sentence Discrimination 7
Methods 8
Results 11
Discussion 12

Experiment 2: Sentence-type Discrimination 14
Methods 15
Results 17
Discussion 18

Experiment 3: Effectiveness of Head-turn Preference 22
Procedure at Assessing Sentence-type
Discrimination
Methods 22
Results 24
Discussion 25

General Discussion 25
References 32
Appendices
Appendix A: Sentences Used in Experiments 34
Appendix B: Graphs 35

iii

List of Figures

Figure 1: Mean looking time duration for novel and old trials 35
as a function of habituation group in Experiment 1.

Figure 2. Mean looking time duration for novel and old trials 36
as a function of habituation group in Experiment 2.

Figure 3. Mean looking time duration for novel and old trials 37
as a function of blocks in Experiment 3.
iv

Abstract
Three studies examined typically developing English-learning infants between 7- and 12-
months to determine when they could distinguish between interrogatives and
declaratives. We used two habituation paradigms and measured looking times to
determine whether they were able to make the distinction. Experiments 1 and 2 used a
modification of the Visual Habituation Procedure (Houston et al., 2007). Experiment 1
evaluated infants’ ability to distinguish between two sentences. Experiment 2 assessed
whether infants could distinguish between sentence types (declaratives and
interrogatives). Motivated by the pattern of positive and negative findings in Experiments
1 & 2, Experiment 3 evaluated the effectiveness of the Head-turn Preference Procedure
(HPP) at assessing the sentence-type discrimination ability. Experiment 1 indicated that
9- and 12-month-olds could distinguish between sentences. Experiment 2 found evidence
that infants as young as 7-month-olds could discriminate these broad classes of sentences,
whereas no such evidence was found for 8- and 9-month-olds. Experiment 3 suggests
that HPP may not be the most effective method for assessing sentence-type
discrimination abilities.

1

Can Infants Discriminate Between Declaratives and Interrogatives?

The purpose of this project was to determine whether infants could discriminate
between sentence types, with a particular focus on declaratives and interrogatives. In
English, speakers make distinctions between sentence types based on cues such as word
order and final pitch. Declaratives are characterized by a falling pitch and subject verb
object word order. Interrogatives are often characterized by syntactic properties such as
the use of wh- words (e.g. who, what) and auxiliary inversion (e.g. “Did you clean your
room this morning?”). Although many studies have examined the types of cues adults
and young children use to distinguish between sentence types, little is known about how
the sentence discrimination ability develops in infants and the cues they use to distinguish
sentence types. This study is also unique in that no previous research has examined
sentence-type distinctions in preverbal infants.
Two important aspects of speech that infants use to extract information from
fluent speech are syntax and prosody. Syntax involves learning the structural aspects of
sentences, including word order, which helps infants differentiate between sentence
types. Prosody is a quality of speech that is involved in rhythm, stress, and intonation and
has three key features: fundamental frequency (perceived pitch), duration, and intensity
(perceived loudness). These three aspects of prosody allow speakers to parse fluent
speech and learn rhythmic cues relevant to their native language (Johnson & Jusczyk,
2001; Thiessen & Saffran, 2003).

2

Developmental Aspects
Adult speakers are adept at using the primary features of prosody to distinguish
sentence types. For example, perceptual studies of adults have shown that European
Portuguese speakers rely primarily on fundamental frequency to distinguish sentence
types (Falé & Faria, 2007); Russian and Japanese speakers use final rising intonation
(Makarova, 2001); and Russians speakers are influenced by pitch peak alignment (the
highest pitch in a sound) ( Makarova, 2007). These studies demonstrate that adults are
able to make sentence-type distinctions using the acoustic properties relevant to their
language.
While many studies of adults have focused on their perceptual abilities when it
comes to making sentence-type distinctions, most research on children has examined
their production abilities. Studies of children's early production of prosody in English
showed that with age, their ability to imitate intonation contours improved, and they
began to use different cues to distinguish between sentence types. For example, Patel and
Grigos (2006) found that 4-, 7-, and 11-year olds produced noticeable differences
between sentence types by elongating the final syllable of interrogatives more than
declaratives. However, in perceptual studies, when asked to make a judgment on
sentence-type distinctions, typically, 4-year-olds used syllable duration, whereas 11-year-
olds used fundamental frequency as adults do (Loeb & Allen, 1993; Patel & Grigos,
2006).
Most studies of young language learners have focused on subjects who are
already capable of speech. Therefore, we know a great deal about when children are able
3

to produce this distinction, but not when they begin to become aware of it. Some studies
have shown that infants can make rhythmic distinctions between languages almost from
birth. Infants can discriminate between their native language and a foreign language as
young as two days old (Mehler, Jusczyk, Lambertz, Halsted, Bertoncini, & Amiel-Tison,
1988), and between two non-native languages with different prosody during the first six
months of life as long as the languages come from different rhythmic classes (Moon,
Cooper, & Fifer, 1993). However, if the languages have similar prosody (e.g., English
and Dutch), infants cannot make the distinction (Christophe & Morton, 1998). Between
6- and 9-months, infants begin to perceive the prosodic properties of words in their native
language. The ability to make rhythmic distinctions between languages could provide
infants with a tool for making similar distinctions within their own language.
In general, these studies suggest that there is a developmental sequence that
begins at birth. Typically, infants begin by picking up on language-specific cues, such as
rhythm, which enables them to discriminate between languages. With age, children
develop sensitivities to complex prosodic cues, such as fundamental frequency.
This sensitivity to complex prosodic cues could allow infants to make distinctions
within their own language such as sentence-type distinctions. The current studies aim to
discover when infants develop this prosodic sensitivity and when they can make
sentence-type distinctions.
Measurement
Most studies of speech discrimination abilities in infants have involved cross-
sectional designs that examined group differences. However, a focus on individual
4

differences would provide an opportunity to assess change over time with regard to
typical and atypical developmental patterns. Moreover, examining individual infants’
speech abilities (perception and production) could prove useful to clinicians in assessing
language delays. The current studies examined sentence and sentence-type
discrimination abilities with the eventual goal of assessing individual differences.
Although previous research has taken both prosodic and word order cues into account,
our studies did not make a distinction, focusing instead on global discrimination abilities.
One of the only methods currently available for examining individual differences
is the habituation procedure developed by Houston, Horn, Qi, Ting, and Gao (2007).
Houston et al.’s (2007) habituation procedure is a modification of the Visual Habituation
Paradigm (VHP). Traditionally, the VHP involves manipulating sound and visual
displays. When looking time decreases and infants have reached a habituation criterion,
they are presented with a novel sound and the same visual display. If infants demonstrate
an increase in looking time in response to a novel stimulus, this is taken as evidence that
infants are able to discriminate between the pre- and post-habituation auditory stimuli.
Houston et al. (2007) altered VHP by changing the ratio and spacing of novel and
old trials. Normally, VHP presents trials in an equal ratio, alternating presentation of
novel and old trials. Instead, Houston et al. (2007) presented an uneven ratio with novel
trials pseudo-randomly interspersed between groups of old trials, providing periods of re-
habituation, and thereby increasing the dishabituation effect to each novel stimulus trial.
Houston et al.’s (2007) procedure examined individual differences in infant
speech discrimination abilities using two different audiovisual non-word tokens. Highly
5

contrastive non-words were chosen to make it easier for infants to discriminate between
them. To make the effect of novelty more robust and consistent throughout the test phase,
infants were habituated to one of the two non-word tokens. During the test phase infants
were presented with four novel-alternating trials and 10 old-alternating trials. Novel-
alternating trials consisted of one novel token and one token from the habituation phase.
Old-alternating trials consisted of two tokens from the habituation phase. The first token
in both the old-alternating and novel-alternating trials was the same. The first two trials
in the test phase consisted of one old-alternating and one novel-alternating trial, with the
rest pseudo-randomized so novel trials would not be presented consecutively.
Houston et al. (2007) conducted analyses on both group and individual means.
The group analyses produced typical VHP results, indicating that infants demonstrated
robust looking time differences and a clear novelty preference. When Houston et al.
(2007) compared mean looking times to the first novel trial and the first old trial of the
test phase, there was a significant main effect of trial type, suggesting that when a large
number of participants were tested, this procedure was able to detect discrimination in
infants with only two trials.
To assess individual performance, Houston et al. (2007) performed an auto
regression analysis on individual infant’s data. Auto regression analysis was an
innovative application in VHP. This analysis allows comparisons of novel and old
stimuli, factoring out sequential effects of one trial on the next. It is a more robust
analysis of variables given a long series of test trials.
6

Houston et al. (2007) also examined the test-retest reliability of their measure by
examining infants’ performance across two different sessions separated by one to three
days. The results showed that eight out of 10 infants demonstrated stable performance
across testing sessions.
Houston et al.’s (2007) method differs from previous habituation procedures in
that the ratio of old- to novel-alternating trials provides periods of re-habituation. Re-
habituation renews the novelty effect, providing more data points per subject using the
same material and allowing researchers to conduct individual assessments. The goal of
the current studies was to assess individual differences in sentence-type discrimination
ability. Houston et al.’s (2007) method provides a potential procedure for doing this.
However, since it was originally tested with single nonsense words, the method may not
be effective with more complex stimuli such as sentences. Nevertheless, these efforts
represent an important step in determining whether infants are capable of discriminating
between sentence types.
Given the good test-retest reliability of Houston et al.’s (2007) method, it would
be interesting to test and apply Houston et al.’s (2007) method to more complex stimuli,
such as sentences. The first goal of the current experiments was to determine when
infants can discriminate between sentence types (declarative versus interrogative). The
second goal was to find the best methodology for making this assessment. Three
experiments were designed to address these goals. Experiments 1 and 2 explored the
efficacy of a new habituation procedure, which has only been tested on word
discrimination tasks thus far, to determine if it could detect differences in discrimination
7

abilities with more complex stimuli such as sentences. Experiment 1 tested infants’
ability to discriminate between two sentences to determine whether they could make
simple discriminations. Experiment 2 evaluated whether infants could discriminate
between sentence types when provided with multiple exemplars of each. Experiment 3
evaluated how the Head turn Preference Procedure, a procedure for evaluating infants'
auditory perceptual abilities, compared as a method for assessing infants' sentence-type
discrimination abilities.
Experiment 1
The aim of the first experiment was to determine whether infants could
discriminate between two sentences (“Would you like to play?” (Sent1) and “Let’s use
the blue crayon.” (Sent2)). We also evaluated whether Houston et al.’s (2007) method
was useful for making broad distinctions between sentences with the eventual goal of
looking at individual differences. This experiment was a replication and extension of
Houston et al.’s (2007) Experiment 2 using sentences instead of single non-word tokens.
If infants looked longer at the novel stimuli this would suggest that they were able to
distinguish between sentences and that Houston's procedure was effective at assessing
infants’ discrimination abilities with complex stimuli.
The current study examined typically developing English-learning 9- and 12-
month olds to assess their global sentence discrimination ability. We chose to start with
9-month-olds because research has shown that they can already use prosodic patterns to
segment words from fluent speech and are attuned to the rhythmic pattern of their native
language (Curtin, Mintz & Christiansen, 2005; Johnson & Jusczyk, 2001; Jusczyk, 1993
8

as cited in Gerken & Aslin, 2005). 12-month-olds provided a comparison source,
especially if infants were not demonstrating strong discrimination ability at 9-months.
Methods
Participants:
Forty typically developing English-learning infants [nineteen 9-month-olds (M =
9.22 months, SD = 0.28 months) and twenty-one 12-month-olds (M = 12.22 months, SD
= 0.35 months)] were recruited from county birth records, contacted first by letter, and
then by phone or e-mail to schedule an appointment. Infants only participated at one time
point.
Parents were informed at the beginning of the study that participation was
voluntary and they were free to withdraw from the study at any time.
Apparatus:
Sentences were presented by Habit (Cohen, Atkinson, & Chaput, 2004) on a Mac
computer. A Sony DCR-TRV22 NTSC Handycam was used to provide experimenters
with a visual recording of the child.
Stimuli:
Stimuli were recorded by a female native English speaker in an infant-directed
register, which exaggerates prosodic dimensions and is intrinsically appealing to infants
(Fernald, 1984). Stimuli were matched on number of syllables and duration. Sentences
were five syllables, with final syllable duration averaging 0.25 seconds (Sent1 mean =
0.2865, Sent2 mean = 0.2230). Sentences were adjusted to a mean volume of 53.5
decibels (+ 2.5 decibels) for Sent1 and 53 decibels (+ 3 decibels) for Sent2.
9

Habituation consisted of four tokens of the same sentence (e.g. "Let's use the blue
crayon”) (e.g. Sent2a-Sent2d). There were two types of test trials: novel- and old-
alternating trials. Old-alternating trials consisted of two tokens of the habituation
sentence, one version that had been included in the habituation phase (e.g.Sent2a) and
one new version of the sentence (e.g. Sent2e). Novel-alternating trials consisted of the
same version of the habituation sentence used in the old-alternating trials (e.g. Sent2a)
and the non-habituation sentence (e.g. "Do you want to play?") (e.g. Sent1).
Procedure:
Infants’ sentence discrimination ability was measured using Houston et al.’s
(2007) habituation procedure. They were randomly assigned to one of two habituation
groups, either interrogative (Sent1) or declarative (Sent2) habituation, with random
presentation of old or novel trial first.
Infants were seated in their parent’s lap in a darkened, sound-attenuated room
facing a video monitor during the course of the experiment. A camera under the screen
allowed the experimenter to monitor the child’s preferences throughout the experiment,
and to record these preferences for later reliability testing. The auditory stimuli were
played over the video monitor speakers. The parent wore headphones that played
masking music to prevent the parent from unconsciously influencing the child’s behavior.
The experimenter was not able to hear the audio stimuli through the video monitor and
was blind to the child’s habituation group. Trials ended when the child looked away
from the screen for longer than 2 seconds. Habit recorded the infant’s looking time for
each habituation trial. The experiment took approximately 5-10 minutes.
10

The experiment began with an attention-getter on the screen, a colorful laughing
baby that oriented the child's attention to the screen, and then habituation started.
Habituation lasted until infants met habituation criterion or until they had completed 15
habituation trials. Habit established a habituation baseline by taking the average of the
first two habituation trials and compared this to a moving window of two trials until the
average of two trials was 50% or less than the mean looking time in the first two trials.
Although standard procedure uses a moving window of three trials, pilot data showed that
a window of two trials was more effective. Once the child met habituation criterion,
habituation ended and the test phase began.
Our test phase consisted of 11 trials as opposed to the 14 used in Houston et al.
(2007) because pilot data showed that with up to 15 habituation trials, 14 test trials and a
posttest measure, infants rarely completed the study. Of the 11 trials, three were novel-
alternating trials and eight were old-alternating trials. The first two trials consisted of one
novel-alternating and one old-alternating trial. The other nine trials were pseudo-
randomized so novel trials did not appear consecutively. Standard protocols for
counterbalancing and subject exclusion criteria were followed. Houston et al. (2007)
showed that this kind of testing sequence allows robust and reliable detection of
discrimination in individual subjects, but has only been tested with simple stimuli in
speech discrimination tasks.
Infants’ general arousal level was tested before and after the experiment, with a
computer graphic of a geometric shape (a yellow square on a black background) moving
back and forth across the screen accompanied by a Shepard tone. This is a common
11

method used in habituation studies to determine whether decreased looking time could be
attributed to habituation or general fatigue. To that end, one of the inclusion criteria for
the study was that infants maintain looking time during the posttest trial of at least 50%
of the pretest trial duration. If infants did not maintain at least 50% of their pre-test
looking time, this could suggest that some other factor such as fatigue or fussiness could
account for lack of results, rather than general disinterest in the stimuli. This was not an
issue though, and all subjects met this criterion.
Parents were told that they could expect their child to become disinterested during
the study, and this could translate into wiggly behavior. If this should happen, the best
time to readjust their child was when the laughing baby was on the screen, which
indicated that no data was being collected.
Results
The goal of this experiment was to determine whether infants could discriminate
between two sentences. To establish if infants were making a global distinction between
sentences, we conducted a paired t-test on average looking time data for novel-alternating
versus old-alternating trials. Novel-alternating trials had a mean of 7.74 s (SD = 4.35 s)
and old-alternating trials had a mean of 6.00 s (SD = 2.65 s). A paired t-test found a
significant difference between trial types, t (39) = 2.53, p = 0.015. A cursory analysis of
habituation trials suggested that infants varied considerably in their exposure to the
habituation stimuli before reaching habituation criterion. Since habituation is a crucial
component for determining whether infants can discriminate between stimuli, we
investigated the effects of length of habituation on trial type preferences. We divided
12

infants into two groups based on their total habituation time, using the median as the
midpoint. To evaluate infants’ sentence discrimination abilities, we compared the mean
looking time data using a repeated-measures ANOVA with Trial Type (old- alternating
vs. novel-alternating) as the within-subjects variable and Habituation Group (long versus
short total habituation time) as the between subjects variable. There was a significant
main effect for Trial Type, F (1, 38) = 10.547, p = 0.002, and Habituation Group, F (1,
38) = 6.538, p = 0.015, and a significant interaction for Trial Type x Habituation Group,
F (1, 38) = 12.146, p = 0.001. For the short habituation group, the novel trials had a
mean of 6.21 s (SD = 3.85 s) and the old trials had a mean of 5.84 s (SD = 2.97 s). For
the long habituation group, the novel trials had a mean of 10.59 s (SD = 3.86 s) and the
old trials had a mean of 6.29 s (SD = 1.99 s). Effects were carried by the long habituation
group. See Figure 1.
To test for age-related differences, we performed a repeated-measures ANOVA
with Trial Type (novel-alternating versus old-alternating) as the within-subject variable
and Age (9 & 12 months) as the between subjects variables, focusing on the long
habituation group. There was a main effect of trial type, F (1, 12) = 12.999, p = 0.004.
There were no other main effects or interactions.
Discussion
The fact that infants looked longer during the novel-alternating trials than during
the old-alternating trials supports our hypothesis and suggests that infants are capable of
discriminating between two sentences. The interaction between Trial Type and
Habituation Group suggests that infants who have a longer exposure to the habituation
13

material show a more reliable dishabituation effect. It could be that longer habituation
times mean that infants are thoroughly familiar and bored with the habituation sentence
and find the novel sentence especially interesting. This also demonstrates that Houston et
al.’s (2007) method is effective with longer stimuli such as sentences, at least as concerns
effects at the group level. Assessment of individual differences using auto regression
analysis has yet to be performed on these data.
The results of the Trial Type x Age ANOVA suggest that both groups of infants
are capable of distinguishing between sentences.
Since infants were able to differentiate between two sentences, the next step was
to evaluate whether they could discriminate between sentence types in addition to
individual sentences.
14

Experiment 2
Given the results of Experiment 1, we wanted to evaluate infants' ability to
discriminate between sentence-types (declaratives and interrogatives) when given
multiple exemplars of each type. The current study examined typically developing
English-learning infants starting at 7-months with follow-ups at 8- and 9-months using
Houston et al.’s (2007) habituation procedure to determine when infants begin to acquire
the ability to make the distinction between declaratives and interrogatives.
We incorporated follow-ups at 8- and 9-months to assess test-retest reliability and
to study the development of infants’ ability to distinguish between sentence types,
particularly if their ability was not strong at 7-months. (At present, too few infants have
participated at all ages, so test-retest analyses have not yet been performed.) A secondary
goal was to determine whether Houston et al.’s (2007) habituation procedure was
effective at evaluating infants’ sentence-type discrimination ability. We predicted that
infants would be able to use prosodic and word order cues to distinguish between two
sentence types, with an increase in performance over time. Since no one has previously
examined this issue, we were unsure of what to expect and so tested a range of ages under
one year at points where it is known that infants can use prosody to make various
distinctions. This was one of the reasons participants were asked to come in for three
sessions, to assess their developing abilities. Due to a small number of subjects who
came in for multiple assessments, we also recruited several 9-months-olds who had not
participated at an earlier time point, to assess general differences and similarities across
age groups cross-sectionally.
15

Methods
Participants:
Twenty-four typically developing, English-learning infants were recruited
[twenty-one 7-month olds (M = 7.24 months, SD = 0.20 months), eight 8-month-olds (M
= 8.36 months, SD = 0.12), and eight 9-month-olds (M = 9.33 months, SD = 0.31)]. (Due
to the small number of returning subjects and inclusion of the cross-sectional component,
analysis treated age as a between-subjects variable. Many of the subjects participated at
2 or sometimes 3 time-points, which accounts for why the age breakdown does not equal
the total number of subjects.) Infants were examined over three consecutive months,
beginning at 7 months, with follow-ups at 8 and 9 months. Eight of the 24 subjects
returned for the 8-month assessment. Eight infants came in for the 9-month assessment;
3 of the 8 infants participated at all three time points, two came in for the 7- and 9-month
assessments and three only came in for the 9-month assessment. Five participants were
removed from analysis due to experimenter error (n=3) and failure to complete the study
(n=2). They were recruited from county birth records, contacted first by letter, and then
by phone or e-mail to schedule an appointment.
Apparatus:
The experimental setup was the same as used in Experiment 1.
Stimuli:
Stimuli were recorded by a female native English speaker in infant-directed
speech, and matched on length in syllables and duration. Stimuli were relatively short
because previous studies reported failure with stimuli that are too long due to auditory
16

memory limitations (Massaro, 1987). Sentences were eight syllables, with final syllable
duration averaging 0.20 seconds (0.1079-0.3550). A full list of stimuli can be found in
the Appendix.
Forty-eight sentences (24 declaratives and 24 interrogatives) were recorded three
times each and the clearest version with the correct intonation contour was selected. This
was then narrowed down to nine sentences the author felt best represented the desired
intonation contours. Volume was adjusted so that all sentences had a mean of 58 decibels
(+ 11.3 decibels).
Habituation consisted of eight sentences of one sentence type (e.g. interrogative).
There were two types of test trials: novel- and old-alternating trials. Novel-alternating
trials presented pairs of sentences, one of the habituation type (e.g., an interrogative) and
one of the non-habituation type (e.g., a declarative).These sentences were completely
novel; infants heard them for the first time during the testing phase. Old-alternating trials
presented pairs of sentences, both of the habituation type (e.g., two interrogatives). The
old-alternating trials shared their first sentence, which infants heard in the habituation
phase. The second sentence in each pair was the habituation type, but infants heard it for
the first time during the testing phase. Each subject heard two sets each of novel-
alternating sentences and old-alternating sentences.
Procedure:
The procedure was the same as Experiment 1.

17

Results
The goal of this experiment was to determine whether infants could distinguish
between declaratives and interrogatives. To determine whether infants were making the
sentence-type distinction, we conducted a paired t-test on average looking time data for
novel-alternating versus old-alternating trials. Novel-alternating trials had a mean of 5.69
s (SD =3.60 s) and old-alternating trials had a mean of 6.30 s (SD = 2.91 s). A paired t-
test failed to find a significant difference, t (37) = -1.42, p = 0.16. Given the differences
found in Experiment 1 between infants based on habituation time, we divided infants into
two groups, based on length of habituation, and compared mean looking times to the
novel-alternating and old-alternating trials within these habituation groups. For the short
habituation group, novel trials had a mean of 5.30 s (SD = 3.38 s) and old trials had a
mean of 5.56 s (SD = 2.65 s). For the long habituation group, novel trials had a mean of
6.09 s (SD = 3.86 s) and old trials had a mean of 7.05 s (SD = 3.04 s). See Figure 2. We
performed a repeated-measures ANOVA with Trial Type (novel-alternating versus old-
alternating) as the within-subject variable and Habituation Group (long versus short
habituation time) as the between subjects variables. There were no significant main
effects or interactions.
To determine if there were any significant differences between trial types, we
conducted paired t-tests on average looking time data for 7-, 8- and 9-month-olds. For 7-
month-olds, novel-alternating trials had a mean of 5.10 s (SD = 2.03 s) and old-
alternating trials had a mean of 6.30 s (SD = 2.36 s). For 8-month-olds, novel-alternating
trials had a mean of 6.19 s (SD = 5.36 s) and old-alternating trials had a mean of 7.34 s
18

(SD = 3.97 s). For 9-month-olds, novel-alternating trials had a mean of 6.68 s (SD =
4.64 s) and old-alternating trials had a mean of 5.16 s (SD = 2.83 s). There was a
significant effect for 7-month-olds, t (20) = -2.22, p = 0.038, a marginal trend towards
significance for 9-month-olds, t (7) = 1.82, p = 0.11, but not for 8-month-olds, t (7) = -
1.04, p = 0.33.
Discussion
The results of Experiment 2 show age-related differences in sensitivity to
differences between interrogatives and declaratives, as assessed by the modified VHP
procedure. Seven-month-olds showed a significant difference in looking times, whereas
9-month-olds showed a marginal trend towards significance and 8-month-olds did not
show a significant difference. These differences in trial type preferences suggest that
Houston et al.’s (2007) method may not be effective for all groups using the same
stimuli. It also suggests that how information is processed changes over time, perhaps as
infants learn to integrate prosodic and syntactic cues.
Concerning the direction of the response in 7-month-olds, although the preference
for old vs. novel stimuli was unexpected, it is not unexplainable. One possibility is that
although infants are meeting the 50% or less habituation criterion, they are not fully
habituating, causing them to fixate on familiar rather than novel stimuli. (Recall that
standard habituation procedures use a window of three trials as a habituation criterion,
but our pilot data found that three trials were too long for 7-month-olds. Perhaps a longer
habituation time would yield a novelty, rather than a familiarity preference). Another
possibility is that infants recognize a particular property of the stimuli, which generates a
19

familiarity response that is stronger than the novelty effect (Aslin, 2007). A third
alternative is that infants are attending to different acoustic properties during habituation
and the test phase causing them to prefer the familiar trials rather than the novel trials.
In contrast, 9-month-olds demonstrated a marginal trend towards a novelty
preference, which may be supported by a larger sample. Assuming that a larger sample
of 9-month-olds would demonstrate a significant novelty preference, this shift from a
familiarity to a novelty preference could indicate that the way infants process sentences
changes between 7- and 9-months.
Previous research has found that infants preferentially attend to different cues at
different stages of development (Curtin et al, 2005; Johnson & Jusczyk, 2001; Thiessen
& Saffran, 2003), which could imply that a seeming lack of response to a novel stimuli
may in fact indicate infants' greater attention to other cues, or more complex processing
of cues. For example, in the domain of word segmentation, at 7-months, although infants
are sensitive to both prosodic and statistical cues, they preferentially attend to prosodic
cues such as stress (Curtin et al, 2005; Johnson & Jusczyk, 2001). By 9-months, infants
treat cues differently as they are learning the correlation of prosodic cues and statistical
cues in a more complex manner of processing (Thiessen & Saffran, 2003).
Perhaps that is what is happening here: infants around 8- to 9-months might be
starting to integrate the prosodic and syntactic cues that correlate with the
interrogative/declarative distinction in English, and thus may treat those cues differently
than 7-month-olds. Seven-month-olds’ strong familiarity preference indicates that they
are capable of discriminating between sentence types, even if it is in an unexpected
20

direction. It seems likely that 8- and 9- month-olds should be similarly capable of
making the sentence-type distinction. Perhaps these older infants are focusing on other
properties of the sentence, giving the impression that they cannot make the distinction. It
may be that Houston et al.’s (2007) method is not effective with older infants. It is also
possible that since infants are starting to integrate prosodic and syntactic cues around 8-
to 9-months, it may require a different combination of cues to demonstrate discrimination
in these older infants.
Nevertheless, it is clear is that 7-month-olds can discriminate between sentence
types. However, this study was unable to answer the question of whether 9-month-olds
were unable to discriminate between sentence types (which seems unlikely) or whether
Houston et al.’s (2007) method was the most effective for assessing this ability. One way
to test this hypothesis would be to evaluate subjects of the same age with a different
methodology.
There is the additional possibility that the small sample size could have caused the
lack of results. We were only able to recruit eight 9-month-olds and only three of those
subjects participated at all three time points with two more only participating at 7- and 9-
months. Having such uneven groups makes it difficult to draw comparisons between the
two groups. It is also unfortunate that more 7-month-olds were not able to come back for
one or both of the follow-up visits, and thus we were unable to track the development of
the sentence-type discrimination ability over a three-month period.
To rule out methodology as the possible cause of the lack of results, Experiment 3
explored the use of the Head-turn Preference Procedure (HPP) (Kemler Nelson, Jusczyk,
21

Mandel, Myers, Turk & Gerken, 1995), to determine if this method was more capable of
assessing infants’ sentence-type discrimination abilities.
22

Experiment 3
It was unclear from Experiments 1 and 2 whether 9-month-olds were unable to
discriminate between declaratives and interrogatives due to their age, or whether Houston
et al.’s (2007) methodology was unsuitable for older infants.
The aim of this experiment was to discover whether the Head-turn Preference
Procedure (HPP) was more effective at assessing infants’ sentence-type discrimination
ability than Houston et al.’s (2007) method. While Houston et al.'s (2007) method
demonstrated that 7-month-olds could discriminate between sentence types, the method
may not be effective using the same stimuli for every age group. HPP might be better
suited for longer stimuli and/or for initial exposure durations that might not lead to
habituation. If HPP demonstrates a novelty preference that was not found with Houston
et al.’s (2007) method, this would suggest that it was a methodological issue.
Methods
Participants:
Twenty-three typically developing English-learning 9-month-old infants were
recruited from county birth records, contacted first by letter, and then by phone or e-mail
to schedule an appointment. Eleven participants were removed from analysis due to
experimenter error (n=6), failure to complete the study (n=1), and exclusion criteria
(three or more trials shorter than 2000 ms or two SD above the trial mean; n=2).
Apparatus:
Sentences were presented by a PC computer.
Stimuli:
23

This study used the same stimuli as Experiment 1.
Habituation consisted of eight sentences of one sentence type (e.g. interrogative).
There were two types of test trials: novel and old trials. Novel trials presented a pair of
novel non-habituation type sentences (e.g., declaratives) subjects heard for the first time
during the test phase. Old trials presented a pair of habituation type sentences (e.g., two
interrogatives). The first sentence in the old trial was a new sentence of the habituation
type while the second was a sentence infants heard during the habituation phase. Each
subject heard one set of novel sentences and one set of old sentences.
Procedure:
Infants were assessed with a version of HPP to evaluate their ability to distinguish
between sentence types. Infants were randomly assigned to one of two habituation
groups, either declarative or interrogative habituation, with random presentation of old or
novel trial first.
Infants were seated in their parent’s lap in a darkened, sound-attenuated room
during the course of the experiment. Infants were initially facing forward and looking at a
red flashing light with the opportunity to look at either of two yellow lights, one on either
side of the room. The auditory stimuli were played through speakers positioned beneath
the yellow lights. Trials ended when the child looked away from the light for longer than
2000 ms. The computer recorded infants looking time during each trial. The experiment
took approximately 5-10 minutes.
When the child was settled and facing the red light, the red light was extinguished
and the experiment began with habituation. Infants were habituated to several examples
24

of one sentence type (e.g. interrogative) for approximately 80 seconds. This was
followed by a series of contingency trials, which used a tone to demonstrate that when the
child looked at one of the side lights, a sound would play until they looked away for 2000
ms or until the entire stimulus had been played. The contingency phase was immediately
followed by the test phase, which consisted of eight trials: four novel trials and four old
trials. The first two trials consisted of one novel and one old trial. The computer
randomly presented the other six trials ensuring that each stimuli was heard from both
speakers and that the order of stimuli and order of location were independent of the
infant’s behavior. Standard protocols for counterbalancing and subject exclusion criteria
were followed.
Parents were told that if their child should become wiggly, the best time to
readjust their child was when the red light was flashing, which indicated that no data was
being collected.
Results
The goal of this experiment was to determine whether methodology or age
accounted for the lack of results in Experiments 1 and 2. To establish if HPP was a more
effective procedure than Houston et al.’s (2007) procedure for assessing infants’
sentence-type discrimination ability, we conducted a paired t-test on average looking time
data for novel versus old trials. Novel trials had a mean of 11.96 s (SD = 6.76 s) and old
trials had a mean of 12.34 s (SD = 8.44 s). A paired t-test failed to find a significant
difference, t (22) = -0.232, p = 0.818. To determine the effectiveness of HPP, we
compared the mean looking time data using a repeated-measures ANOVA with Trial
25

Type (old vs. novel) as the within-subjects variable and Block (1, 2, 3 & 4) as the
between subjects variable (See Figure 3). There were no significant main effects or
interactions.
Discussion
These results suggest that either infants cannot distinguish between sentence types
at 9-months or that HPP is not sensitive enough to assess the sentence-type
discrimination ability. Given that the purpose of this experiment was to determine if HPP
was more effective at evaluating sentence-type distinctions, the lack of significant results
suggests that it was not more effective.
These results, combined with the results of Experiment 2, imply that age may be
responsible for the lack of results. However, without any data to support this, we cannot
completely rule out methodology.
General Discussion
The results of these three experiments suggest one of two things: 1) even though
7-month-olds are clearly discriminating between sentence types, 9-months have lost the
ability to distinguish between declaratives and interrogative (which seems highly
unlikely) or 2) these methodologies are not effective for all age groups with the current
stimuli.
The results of Experiments 1 suggest that Houston et al.’s (2007) methodology
can assess individual sentence discrimination ability in infants at 9- and 12-months and is
effective with more complex stimuli, such as sentences. Experiments 2 and 3 found that
sentence-type discrimination ability was correlated with age, such that 7-month-olds
26

demonstrated a familiarity preference and 9-month-olds demonstrated a marginal trend
towards a novelty preference. These results suggest that Houston et al.’s (2007)
methodology may not be effective for assessing sentence-type discrimination abilities
with the same stimuli for all age groups.
We assessed 9-month-olds’ abilities in Experiment 3 in an attempt to explain the
results of Experiment 2, which found that 7-month-olds could discriminate between
sentence types but 9-month-olds were not demonstrating this ability. Previous research
has shown that 9-month-olds are capable of making a number of prosodic distinctions.
By 9-months, infants have begun to recognize the stress and rhythmic patterns found in
their language (Jusczyk, 1993 as cited in Gerken & Aslin, 2005). This includes a
preference for their native stress pattern (Jusczyk, Cutler & Redanz, 1993 as cited in
Gerken & Aslin, 2005) including preferring stress (prosodic) cues to statistical cues for
segmenting words from fluent speech at 8-months (Johnson & Jusczyk, 2001). Infants
have also shown a preference for phrase boundary stimuli when pauses occur at phrase
boundaries rather than within the phrase, but only when produced in infant directed
speech (Jusczyk, Hirsh-Pasek, Kemler Nelson, Kennedy, Woodward & Piwoz, 1992 as
cited in Gerken & Aslin, 2005). Clearly they are picking up on other prosodic cues and
can use them to make a variety of distinctions. Why shouldn't they be able to distinguish
declaratives from interrogatives?
As infants begin integrating syntactic and prosodic cues between 7- and 9-months,
this could influence their preference for novel or old stimuli as they attempt to reconcile
27

syntactic and prosodic cues. It may also have an impact on the types of stimuli and
methodology most suitable for each age group.
This lack of sensitivity to novel stimuli could indicate two things: 1) Houston et
al.’s (2007) procedure is not an effective method for assessing sentence-type
discrimination in 9-month-olds or 2) 9-month-olds may be in the process of integrating
prosodic and syntactic cues and thus may require a different combination of cues within a
sentence to evoke a novelty effect.
The 7-month-olds demonstrated very promising results, albeit in the opposite
direction from our predictions. Given the large sample size and robust effect, they are
clearly discriminating between sentence types. The fact that they are discriminating and
the older infants were not suggests that this methodology may not be suitable for older
infants.
Limitations:
One potential limitation is the fact that infants hear more interrogatives (40%)
than declaratives (30%) (Newport, 1977) in daily speech and could be more sensitive to
them, which could bias their perception. This does not seem to have been born out in our
results. While infants may not have demonstrated a novelty preference in Experiments 2
and 3, 7-month-olds are definitely showing a familiarity preference, indicating that they
can make a distinction between sentence types even if it did go against our predictions.
Another concern is that infants may require visual as well as acoustic cues (such
as facial expressions) to be able to distinguish acoustically between sentence types. A
28

future study could provide video of the speaker as well as audio cues to determine if both
are necessary for sentence-type discrimination.
A further concern is that although we sent out brochures to a large number of
potential subjects, we had a response rate of 1-2% who chose to participate in the study.
Our sample may not be generalizable to the larger population.
Applications and implications:
These studies were designed to address gaps in the literature, and could have
implications for theories of syntax, children's early representations of language, and
abnormal language development. These studies could add significant new knowledge to
the types of distinctions pre-verbal infants can make about grammatically different
sentence types. It could have broader impacts in theories of child language acquisition. It
could also affect our understanding of early language perception for individuals with
language impairments, by examining the course of development and sensitivity to
prosodic features in infants at risk for language impairments.
At present, there are few available methods for assessing individual infants’
speech abilities (perception and production), a tool that clinicians could use to assess
language delays. A reliable measure for assessing individual differences could help us
determine the timeline for typically developing individuals, who could then serve as a
comparison for assessing atypical individuals. This is important because if we can
determine when typically developing infants are able to make a distinction, it could help
clinicians identify children with abnormal language development and offer them services
that could help them lead more normal lives.
29

Future research:
The current goal of these studies was to determine whether infants were making
global acoustic distinctions between sentences types. The next step is to evaluate
individual differences in sentence discrimination abilities. We did not explore the use of
auto regression analysis to examine individual differences in the sentence discrimination
ability. It might be informative to examine 9-month-olds data using this technique, as
they showed considerable variability. In addition, our studies were not specific enough to
determine if infants were responding to prosodic or word order cues within the sentences,
to help them discriminate sentence-types. Future research could examine which cues
infants are using to discriminate between sentence types.
Given 7-month-olds familiarity preference, our best next step would be to attempt
to replicate this result with a different methodology (perhaps HPP). We could also
evaluate which cues (prosodic or syntactic) 7-month-olds are using to distinguish
between sentence types. To assess word-order cues, we could present infants with
sentences that have flat intonation and different word order. Infants would be
familiarized to one sentence (e.g. declarative), then tested with a second with different
word order (e.g. interrogative). If they were focusing on prosodic cues, they would not
discriminate based on word order. However, if they were attending to word order, they
should demonstrate the ability to discriminate between sentences. We could assess
prosodic cues using low-pass filtered sentences that remove the speech signals that make
speech comprehensible, leaving only the prosodic contours. Infants would be
familiarized to a sentence with one intonation pattern (e.g. interrogative) then tested with
30

a sentence with the other intonation pattern (e.g. declarative). If infants were attending to
prosodic cues, they should discriminate between the two sentences.
Once we have established a developmental timeline, this will provide a
foundation for detecting groups with language disabilities. Knowing when infants should
be reaching certain milestones will allow pediatricians to potentially catch early signs of
language delays and recommend intervention.
Once normative measures are established, and in particular, a method for
assessing individual differences, future research will evaluate the use of prosody as an
early indicator of autism, since prosodic deficits are common in autism. Prosody is
involved in signaling the difference between types of sentences such as declaratives and
interrogatives (McCann, Peppé, Gibbon, O'Hare & Rutherford, 2006). Since prosody is a
part of speech, we should be able to detect it almost as soon as children begin to speak.
Prosody may even be detectable in preverbal infants’ ability to identify sentence-type
contrasts. Given that siblings of children with autism have a 5-8% greater risk for having
autism and a 10-20% chance of some milder impairment including language delays
(Zwaigenbaum, Thurm, Stone, Baranek, Bryson, Iverson, Kau, Klin, Lord, Landa, Rogers
& Sigman, 2007), any sign of prosodic delays could serve as an early indicator of autism.
Based on the 7-month-olds results, the sentence-type discrimination ability could provide
a diagnostic tool for the early assessment of autism.
In summary, the current studies have provided us with new information about
infants’ sentence discrimination abilities. First, 7-month-olds can discriminate between
sentence types, although the cues they use to make this distinction remain a mystery. If
31

7-month-olds can discriminate, this implies that older infants can as well, and it simply
remains to figure out which cues they are attending to, and what method is best for
assessing the sentence-type discrimination ability. Second, we have found that while
Houston et al.’s (2007) method is effective with 7-month-olds, it seems unsuitable for use
with older infants. It remains to be seen whether a change of methodology or stimuli will
demonstrate discrimination with 9-month-olds. The best course of action for the future is
to further evaluate 7-month-olds sentence type discrimination abilities and the cues they
are using to distinguish between sentences assuming that this will provide a foundation
for evaluating the abilities of older infants and atypical language populations.
32

References
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34

Appendix A
Sentences Used in Experiments

Sentences Used In Experiment 1

1. Do you want to play?
2. Let’s use the blue crayon.

Sentences Used In Experiments 2 & 3

Declaratives
1. Sally bought a green dress and scarf.
2. The spotted brown dog chased his tail.
3. The merry go round broke down today.
4. We’re having French toast for breakfast.
5. I saw Jake yesterday evening.
6. The pink lemonade was too sweet.
7. We planted daffodils today.
8. The cake had red and blue sprinkles.
9. They served steak and mashed potatoes.

Interrogatives
1. Does school start September 18
th
?
2. Did you see a scary movie?
3. The last batter hit a home run?
4. Has the gray house been empty long?
5. Were the flowers on the wall blue?
6. Did you clean your room this morning?
7. What are we having for breakfast?
8. What kind of salad did mom make?
9. What is the brown puppy chewing?
35

Appendix B
Graphs

Figure 1: Mean looking time duration for novel and old trials as a function of
habituation group in Experiment 1.

36

Figure 2: Mean looking time duration for novel and old trials as a function of habituation
group in Experiment 2.
37

Figure 3: Mean looking time duration for novel and old trials as a function of blocks in
Experiment 3.

Abstract (if available)

Abstract Three studies examined typically developing English-learning infants between 7- and 12-months to determine when they could distinguish between interrogatives and declaratives. We used two habituation paradigms and measured looking times to determine whether they were able to make the distinction. Experiments 1 and 2 used a modification of the Visual Habituation Procedure (Houston et al., 2007). Experiment 1 evaluated infants’ ability to distinguish between two sentences. Experiment 2 assessed whether infants could distinguish between sentence types (declaratives and interrogatives). Motivated by the pattern of positive and negative findings in Experiments 1 & 2, Experiment 3 evaluated the effectiveness of the Head-turn Preference Procedure (HPP) at assessing the sentence-type discrimination ability. Experiment 1 indicated that 9- and 12-month-olds could distinguish between sentences. Experiment 2 found evidence that infants as young as 7-month-olds could discriminate these broad classes of sentences, whereas no such evidence was found for 8- and 9-month-olds. Experiment 3 suggests that HPP may not be the most effective method for assessing sentence-type discrimination abilities.

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Asset Metadata

Creator Geffen, Susan (author)

Core Title Can infants discriminate between declaratives and interrogatives?

School College of Letters, Arts and Sciences

Degree Master of Arts

Degree Program Psychology

Publication Date 10/29/2010

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

Tag declaratives,Infants,interrogatives,OAI-PMH Harvest,sentence-type discrimination

Place Name USA (countries)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Mintz, Toben (committee chair), Farver, Jo Ann M. (committee member), Manis, Franklin R. (committee member)

Creator Email sgeffen@usc.edu,Swingchicla@aol.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m3515

Unique identifier UC1276368

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

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