Journal of Memory and Language 40, 62– 82 (1999)
Article ID jmla.1998.2605, available online at http://www.idealibrary.com on
Nine-Month-Olds’ Attention to Sound Similarities in Syllables
Peter W. Jusczyk
Departments of Psychology and Department of Cognitive Science, Johns Hopkins University
Mara B. Goodman
State University of New York at Buffalo
and
Angela Baumann
Department of Communicative Disorders, San Diego State University
Nine-month-old English-learners’ sensitivity to intrasyllabic constituents was explored in seven
experiments using the Headturn Preference Procedure. In each experiment, the infants were exposed
to two types of lists of CVC syllables. Items in the experimental lists shared a particular phonetic
property, whereas items in the control lists were unrelated. The findings indicated that 9-month-olds
are sensitive to shared features that occur at the beginnings, but not at the ends of syllables.
Specifically, the infants had significant listening preferences for lists in which the items shared either
initial CV’s, initial C’s, or the same manner of articulation at syllable onsets. The findings suggest
that infants may first develop sensitivity to internal commonalties that occur at the beginnings of
syllables. © 1999 Academic Press
cabulary, such as an ability to adjust to variability in the production of words that occurs as a
result of differences in talkers (Jusczyk, Pisoni,
& Mullennix, 1992; Kuhl, 1979; Kuhl, 1983) or
in speaking rates (Eimas & Miller, 1980; Miller
& Eimas, 1983). More recently, research has
focused on infants’ capacities for segmenting
fluent speech into word-sized units (Echols,
Crowhurst, & Childers, 1997; Jusczyk & Aslin,
1995; Morgan, 1996; Newsome & Jusczyk,
1995; Saffran, Aslin, & Newport, 1996). What
these studies show is that within their first year,
infants already possess many of the abilities that
are required for learning words and building a
lexicon (Aslin, Jusczyk, & Pisoni, 1997).
Of course, in addition to the knowledge and
capacities that are required for learning and
distinguishing among different words, the mature language learner has also acquired a great
deal of information about the sound structure of
the native language. For instance, a native
speaker-hearer has knowledge of the kinds of
phonetic elements that can appear in words, as
well as what sequences of these elements are
Much of the research on infant speech perception has focused on the skills that learners
need to acquire a lexicon in their native language. Early studies were mostly directed at
examining the kinds of phonetic distinctions
that infants are capable of perceiving (Eimas,
1975; Eimas, Siqueland, Jusczyk, & Vigorito,
1971; Moffitt, 1971; Morse, 1972; Streeter,
1976; Trehub, 1973). The ability to perceive
such distinctions is required for discriminating
one word from another. Subsequently, investigators began exploring other capacities that are
pertinent to learning words and building a voPreparation of this manuscript and support for research
reported here was facilitated by a Research Grant from
NICHD (No. 15795) and a Senior Scientist Award from
NIMH (No. 01490) to PWJ. In addition, MBG received
support from an NIDCD Training Grant (No. 00036). We
thank Thierry Nazzi, Ruth Tincoff, Ann Marie Jusczyk,
Luigi Burzio, Paul Luce, Deborah Kemler Nelson, and an
anonymous reviewer for helpful comments on a previous
version of this manuscript. In addition, we are grateful to
Ann Marie Jusczyk, Amy Gambon-Dennis, Aileen Warden,
and Debra Dombrowski for assistance in recruiting and
testing infants.
0749-596X/99 $30.00
Copyright © 1999 by Academic Press
All rights of reproduction in any form reserved.
62
ATTENTION TO SOUND SIMILARITIES
likely to appear (Pertz & Bever, 1975; Whorf,
1956). In general, investigations of how and
when infants learn about these kinds of properties of native language sound structure have not
received as much attention as those features
more closely related to word learning. A notable
exception to this generalization is the investigation of infants’ perception of nonnative language speech contrasts. Ever since Werker and
Tees (1984) documented a decline in sensitivity
to nonnative contrasts toward the end of the first
year, there has been considerable interest in this
phenomenon and the factors responsible for it
(Best, 1993; Best, Lafleur, & McRoberts, 1995;
Best, McRoberts, & Sithole, 1988; Polka &
Werker, 1994; Werker, 1994b; Werker & Desjardins, 1995; Werker & Lalonde, 1988). However, the decline in sensitivity to non-native
contrasts is not universal (Best et al., 1988), and
declines for nonnative consonant and vowel
contrasts may occur at different points in development (Polka & Werker, 1994).
The decline in sensitivity to certain nonnative
contrasts is generally thought to reflect infants’
increasing experience with and knowledge of
native language sound structure (Best,
19931955; Jusczyk, 1993; Werker, 1994a;
Werker & Pegg, 1992). Indeed, there is growing
evidence that during the latter half of the first
year infants are becoming more closely attuned
to the phonological structure and organization
of their language. For instance, evidence from
several sources suggests that infants are beginning to organize phonological categories. Kuhl,
Williams, Lacerda, Stevens, and Lindblom
(1992) found evidence that 6-month-olds appear to have developed some knowledge of the
internal structure of some native language
vowel categories. Pegg & Werker (1997) report
that although 6- to 8-month-old English learners
distinguish among certain allophones from the
same stop consonant category, 10- to 12-montholds do not. They interpret this finding as an
indication that the older infants are beginning to
form phonemic categories.
Other findings show that between 6 and 9
months of age, infants are developing sensitivity to the prosodic and phonotactic organization
of their language. Jusczyk, Cutler, and Redanz
63
(1993) explored when English-learning infants
first display sensitivity to the predominant stress
pattern of English words (i.e., strong/weak).
They presented infants with two types of lists of
bisyllabic words. All the words on a particular
list had a particular stress pattern. They were
either strong/weak or weak/strong. Six-montholds listened about equally long to both types of
lists. However, 9-month-olds listened significantly longer to the lists of words with the
predominant English stress pattern (see also
Turk, Jusczyk, & Gerken, 1995). Infants at this
same age have also been observed to show some
sensitivity to native language phonotactic patterns. Jusczyk, Friederici, Wessels, Svenkerud,
and Jusczyk (1993) presented infants with lists
of unfamiliar Dutch or English words. The
words from each language were chosen so as to
violate the phonotactics (i.e., constraints on the
ordering of phonetic segments) in the other language. At 6 months, infants displayed no significant preferences for either the English or
Dutch lists. However, at 9 months, Englishlearning infants listened significantly longer to
the English lists, whereas Dutch-learning infants showed similar listening preferences for
the Dutch lists. In a subsequent investigation,
Friederici and Wessels (1993) found that Dutch
9-month-olds listened significantly longer to
lists of items containing phonotactically permissible onset and offset clusters for Dutch than
they did to comparable lists containing impermissible onset and offset clusters. Finally, Jusczyk, Luce, and Charles-Luce (1994) demonstrated that English-learning 9-month-olds, but
not 6-month-olds, appear to be sensitive to the
frequency with which certain phonotactic sequences recur within words in the language.
Specifically, the older infants listened significantly longer to lists of CVC’s containing phonotactic patterns that occur frequently within
English words than to lists with infrequently
occurring phonotactic patterns. The 9-montholds’ listening preference for frequently occurring phonotactic patterns is comparable to the
one that Jusczyk, Cutler, and Redanz (1993)
found for items with the predominant word
stress patterns.
Clearly, the latter half of the first year is a
64
JUSCZYK, GOODMAN, AND BAUMANN
period when infants are picking up much information about the sound organization of their
native language. Many questions remain about
the kinds of units and details that infants are
extracting and encoding from speech input. For
example, there is considerable evidence that
syllables are important processing units for infants (Eimas, 1994; Jusczyk, 1985; Mehler,
Segui, & Frauenfelder, 1981). During the first
few months of life, infants (1) track the occurrence of the same syllable in different utterances
(Jusczyk, Jusczyk, Kennedy, Schomberg, &
Koenig, 1995); (2) show better discrimination
of speech stimuli conforming to syllabic (i.e.,
CVC) than to nonsyllabic (i.e., CCC) structures
(Bertoncini & Mehler, 1982); (3) are attentive
to the numbers of syllables in utterances (Bertoncini, Floccia, Nazzi, & Mehler, 1995; Bijeljac-Babic, Bertoncini, & Mehler, 1993); and (4)
benefit from syllabic organization in remembering speech information (Jusczyk et al., 1995).
Although these findings suggest that syllables
are salient units for young infants, there is also
evidence that infants’ representations become
more fine-grained during the latter half of the
first year. As infants begin to identify those
properties that are characteristic of native language sound patterns, some differentiation of
syllabic representations seems likely. Work by
Hillenbrand (1983) suggests that 6- to 8-montholds may begin to perceive some segmental or
featural organization within syllables. Also, as
noted above, one interpretation of decreases in
sensitivity to nonnative contrasts is that infants
are beginning to develop phonemic categories
(Werker & Lalonde, 1988).
If infants are beginning to respond to elements within syllables, what kind of internal
organization might they perceive? One possibility is that infants simply break syllables down
into a set of units corresponding to their component phonemes. However, a number of linguists have posited that syllables are hierarchically organized into constituents consisting of
an onset (one or more initial consonants) and
rime which in turn consists of a nucleus (usually
a vowel) and a coda which includes one or more
consonants (Fudge, 1969; Fudge, 1988; Goldsmith, 1990; Kenstowicz, 1994; Selkirk, 1982;
Treiman, 1989). Kessler and Treiman (1997)
have shown that the association between vowels
and coda consonants in English syllables is significantly greater than that between vowels and
onsets. Moreover, in a variety of psycholinguistic tasks, Treiman and her colleagues have
found that adult listeners tend to break syllables
into onsets and rimes (Treiman, 1983, 1986;
Treiman & Danis, 1988; Treiman, Straub, &
Lavery, 1994). In addition, there is evidence
that preschool children seem to divide syllables
into the same constituents (Treiman, 1985,
1995; Treiman & Zukowski, 1991, 1996).
Although it seems clear that preschool children have developed some sensitivity to onset
and rime constituents of syllables, little is
known about the origins of this sensitivity to
intrasyllabic structure. When infants first display sensitivity to intrasyllabic components
are they actually responding to onsets and
rimes?
The present study explored 9-month-olds’
sensitivity to intrasyllabic information by examining their responses to commonalties
present in different syllables. For each experiment, lists of CVC items were constructed so
that experimental lists contained items that
shared a common element (such as an initial
consonant). The control lists were composed
of CVC items which were unrelated (i.e.,
there were no elements that were common to
all the items on the lists). In previous experiments in our laboratory (Jusczyk et al.,
1993a,b; Turk et al., 1995), infants have
shown a significant tendency to listen longer
to lists that embodied some regularly occurring sound pattern of the native language.
Given this background, we hypothesized that
if infants detected a regularity among the
items in the experimental lists, such as common subsyllabic elements, they would listen
longer to these lists than to the control lists.
Experiments 1– 4 investigated 9-month-olds’
sensitivity to common VC’s (i.e., shared
rimes), common CV’s, common initial C’s
(i.e., shared onsets), and common V’s. Experiments 5–7 provide a closer examination of
the kind of intrasyllabic information to which
the infants are responding.
65
ATTENTION TO SOUND SIMILARITIES
EXPERIMENT 1
Traditionally, developmental psycholinguists
have hypothesized that word endings are especially important for young language learners
(Blasdell & Jensen, 1970; Echols & Newport,
1992; Peters, 1983; Rayman & Zaidel, 1991). In
his classic paper describing operating principles
for language acquisition, Slobin (1973) enumerates “Pay attention to the ends of words!” as one
of the basic principles. More recently, Echols
(1993) has stressed the importance of attention
to word endings in the early stages of language
acquisition.
Sensitivity to the ends of words has also been
cited as an important step in the development of
language-related activities such as reading (Jusczyk, 1977; Liberman, Shankweiler, Fisher, &
Carter, 1974; Rozin & Gleitman, 1977). Indeed,
there have been a number of investigations suggesting that preschoolers’ sensitivity to rhyme
is a good predictor of success at learning how to
read (Bradley & Bryant, 1983, 1997; Bryant,
Maclean, Bradley, & Crossland, 1990; Stuart,
1995). In addition, studies of young children’s
poetic productions have documented the prevalence of rhyming, even across ages and nationalities (Dowker & Pinto, 1993). Moreover, the
popularity of nursery rhymes and rhyming
books for young children across a wide range of
cultures (Burling, 1966), supports the view that
children are often interested in rhymes. Consequently, we began our investigation of infants’
attention to intrasyllabic structure by examining
whether they are sensitive to the occurrence of
a common rime in a list of different syllables.
In order to explore this question, we used the
Headturn Preference Procedure (HPP) to test
infants with lists of monosyllabic nonsense
words. Nine-month-olds were chosen for the
present study because of previous work indicating that infants at this age have begun to display
sensitivity to language-specific sound properties
(Jusczyk et al., 1993b, 1994; Morgan, 1994).
During the course of the experiment, the infants
heard two types of lists. Half of the lists (Rhyming lists) contained repetitions of syllable rimes
whereas the other half (Control lists) contained
unrelated foils. We hypothesized that if infants
attend to the presence of a common rime element in the items, then they should show significant listening preference for the Rhyming
lists over the Control lists.
Method
Participants
The participants were 24 American infants
(12 males and 12 females). Each of the infants
in this experiment, and in all succeeding ones,
was an American infant from monolingual English-speaking homes. The infants were approximately 9 months old, with a mean age of 39
weeks, 3 days (range 5 37 weeks, 2 days to 41
weeks, 4 days). To obtain the 24 subjects for the
study, it was necessary to test 28. Infants were
excluded for the following reasons: crying (1),
parental interference (2), and unresponsiveness
to the flashing lights (1).
Stimuli
A female, native American English speaker
recorded 16 lists of 12 monosyllabic nonsense
words, all following a CVC pattern. Eight of
these were Rhyming lists containing repetitions
of syllable rimes (VC’s) while the remaining 8
were Control lists containing unrelated foils.
The shared rimes for the 6 test lists were [om],
[ad], [Ut], [eyf], [Ik], and [æb]. With respect to
their frequency of occurrence in English syllables, none of these rimes came from the infrequent vowel– coda combinations reported in
Kessler & Treiman (1997). Examples of rhyming and control lists are shown in Table 1.
The stimuli were recorded in a sound-attenuated room with a Shure microphone. The lists
were digitized on a VAXStation Model 3176
computer at a sampling rate of 10 kHz via a
12-bit analog-to-digital converter. The average
duration of the lists was 20 s (ranging from 19.9
to 21.1 s) and the rms amplitude of the stimuli
was 72. After editing, the lists were transferred
to a PDP 11/73 computer and prepared for presentation.
Design
Each infant was seen for one experimental
session. Each infant heard the same set of four
66
JUSCZYK, GOODMAN, AND BAUMANN
TABLE 1
Examples of Rhyming and Control Lists
Rhyming list
Control list
[bad]
[Tad]
[pad]
[Dad]
[lad]
[mad]
[tad]
[vad]
[jad]
[zad]
[ʃad]
[fad]
[vib]
[deyb]
[töp]
[fæd]
[v«p]
[zut]
[Dim]
[seyk]
[mog]
[jɔp]
[moyf]
[Dat]
stimulus lists during the practice phase. The
order of presentation for the 12 test lists was
randomized for each subject, as was the side of
presentation for each list. A session was completed when the infant received all 12 test lists.
Apparatus
A PDP 11/73 controlled the presentation of
the stimuli and recorded the observers’ coding
of the infants’ headturn responses. The audio
output for the experiment was generated from
the digitized waveforms of the samples. A 12bit D/A converter was used to recreate the audio
signal. The output was fed through anti-aliasing
filters and a Kenwood audio amplifier (KA
5700) to one of the two 7-inch Advent loudspeakers mounted on the side walls of the testing booth.
Procedure
The experiment was conducted in a threesided test booth constructed out of 4 3 6 ft
pegboard panels on three sides and open at the
back. An observer looked through one of the
existing pegboard holes in the front panel to
monitor the infant’s head turns. Except for a
small section for viewing the infant, the remainder of the pegboard panels were backed with
white cardboard to guard against the possibility
that the infant might respond to movements
behind the panel. The test booth had a red light
and a loudspeaker mounted at eye level on each
of the side panels and a green light mounted on
the center panel. Directly below the center light
a 5-cm hole accommodated the lens of a video
camera used to record each test session. A white
curtain suspended around the top of the booth
shielded the infant’s view of the rest of the
room. A computer terminal and response box
were located behind the center panel, out of
view of the infant. The response box, which was
connected to the computer, was equipped with a
series of buttons that started and stopped the
flashing center and side lights, recorded the
direction and duration of head turns, and terminated a trial when the infant looked away for
more than 2 s. Information about the direction
and duration of head turns and the total trial
were stored in a data file on the computer.
Computer software was responsible for the selection and randomization of the stimuli and for
the termination of the test trials. The average
listening times for the rhyming and control lists
were calculated by the computer following the
completion of each session.
A version of the headturn preference procedure was used (for an extensive discussion of
this procedure and its reliability, see Jusczyk, in
press; Kemler Nelson et al., 1995; Polka, Jusczyk, & Rvachew, 1995). Each infant was held
on a caregiver’s lap. The caregiver was seated
in a chair in the center of the test booth. Each
trial was begun by blinking the green light on
the center panel until the infant had oriented in
that direction. Then, the center light was extinguished and the red light above the loudspeaker
on one of the side panels began to flash. When
the infant made a head turn of at least 30° in the
direction of the loudspeaker, the stimulus for
that trial began to play and continued until its
completion or until the infant failed to maintain
the 30° head turn for 2 consecutive s (e.g., if the
infant turned back to the center or the other side,
or looked at the mother, the floor, or the ceiling). If the infant turned briefly away from the
target by 30° in any direction, but for less than
2 s and then looked back again, the time spent
looking away was not included in the orientation time. Thus, the maximum orientation time
for a given trial was the duration of the entire
ATTENTION TO SOUND SIMILARITIES
sample. The flashing red light remained on for
the entire duration of the trial.
Each experimental session began with four
practice trials, two from each blinking light.
Infants’ responses during practice trials were
not recorded and were used only to get the
infants comfortable with responding to the
lights. The same four stimulus lists (2 Rhyming
and 2 Control) were used as practice trials for
all subjects. The test phase began immediately
following the four practice trials and consisted
of the presentation of 12 test lists. An observer
hidden behind the center panel looked through
the peephole and recorded the direction and
duration of the infant’s head turns using a response box. The observer was not informed as
to which side the lists would be playing. In
addition, both the observer and the infant’s
caregiver wore foam earplugs and listened to
masking music over tight-fitting closed headphones (SONY MDR-V600). The masker consisted of loud instrumental music, which had
been recorded with few silent periods. Caregivers and observers reported that with this masker
they were unaware of either the location or the
nature of the stimulus on the trial. Reliability
checks between the live observer and observers
of the videotapes of each session are high, with
correlations ranging from .92 to .96 (see Kemler
Nelson et al., 1995).
Results and Discussion
Mean listening times to the Rhyming and the
Control lists were calculated for each of the 24
subjects. The mean listening times were averaged for the Rhyming lists and the Control lists.
Across all subjects, the average listening times
were 9.85 s (SD 5 3.71 s) for the Rhyming lists
and 9.93 s (SD 5 3.03 s) for the Control lists. A
paired t test indicated that this difference in
average listening times was not significant
[t(23) 5 .191, p . .85]. The lack of a significant
rhyme effect was also evident in an analysis
with lists as a random factor [t(10) 5 0.13, p .
.90].1 Thus, the results indicate that 9-month1
The number of lists is small in this experiment and the
succeeding ones. Hence, the sensitivity of this analysis is
not great. However, the list analysis does provide some
67
olds did not listen significantly longer to the
Rhyming than to the Control lists.
Thus, in contrast to the reports about the
sensitivity of older language learners to rhyme
and word endings, there is no indication that
9-month-olds in the present study were attentive
to the occurrence of a common rime across
different items in a list. Of course, there are a
number of possible explanations for this fact.
Many of the earlier claims about sensitivity to
ends of words dealt mostly with attention to
morphological endings (Peters, 1983; Slobin,
1973) or to word-final syllables. Attention to
these features at a later age may not involve any
special sensitivity to final elements within a
syllable at 9 months.
Another possible explanation for the pattern
observed in the present study (suggested by one
of the reviewers) is that detecting the common
rimes was easy for the infants. Thus, during the
test period, the infants may have become bored
with the Rhyming lists sooner than with the
Control lists. To investigate this possibility, we
examined performance during the first and second half of the test period. These data were
submitted to a repeated-measures ANOVA of a
2 (list type) 3 2 (test period) design. There was
a significant main effect of test period [F(1,23)
5 30.88, p , .0001], indicating that listening
times were longer during the first half of the test
period. However, neither the main effect of list
type [F(1,23) , 1.00] nor the interaction between list type and test period [F(1,23) , 1.00]
was significant. Hence, there was no statistical
support for the view that infants detected the
rimes, but became bored with the Rhyming lists
during the test period.
Accordingly, we decided to consider another
possible explanation for the lack of a significant
preference for the common rimes, namely, that
infants at this age may not yet respond to any
intrasyllabic similarities. To explore this possibility, we decided to investigate 9-month-olds’
sensitivity to other kinds of intrasyllabic similarities.
indication of whether any significant effects observed for
the experimental lists were carried by only one or two lists,
rather than the lists in general.
68
JUSCZYK, GOODMAN, AND BAUMANN
EXPERIMENT 2
TABLE 2
As noted earlier, the salience of word endings for language learners has often been emphasized in the language acquisition literature
(Echols, 1988; Peters, 1983; Slobin, 1973). At
the same time, there have been suggestions
that the beginning of words might also be
particularly salient for language learners
(e.g., Peters, 1983; Slobin, 1973). With regard
to their speech production capacities,
9-month-olds are often said to be in the canonical (Oller, 1980) or reduplicated (Koopmans van Beinum & van der Stelt, 1986;
Roug, Landberg, & Lundberg, 1989; Stark,
1980) babbling stage. During this time, their
vocalizations are usually characterized as taking the form of a true consonant and a fully
resonant nucleus or vowel. In other words,
these productions tend to be sequences of
CV’s. The notion that CV’s might be particularly salient structures for language learners
actually fits with the views of many phonologists who have argued that CV’s constitute
the unmarked forms of syllable structures in
the world’s languages (Clements & Keyser,
1983; Prince & Smolensky, 1996). Finally, it
has sometimes been suggested that because
speech sounds are often coarticulated, adult
listeners may process speech in terms of units
corresponding to demisyllables (Fujimura,
1976, 1979; Fujimura & Lovins, 1982) or
diphones (Klatt, 1979, 1986).
Given this background, we decided to investigate whether 9-month-olds might detect
similarities involving the initial CV portions
of CVC syllables. As in the previous experiments, two types of CVC lists were constructed. Half of these (Shared CV lists) contained items that shared their initial CV
portions but differed in their final consonants,
whereas the other half (Control lists) contained CVC’s that were unrelated to each
other. Once again, we expected that if
9-month-olds are attentive to similarities involving the initial CV portions of the syllables, then they should prefer the Shared CV
lists to the Control lists.
Examples of Shared CV and Control Lists
Shared CV list
Control list
[f«t]
[f«m]
[f«D]
[f«n]
[f«g]
[f«b]
[f«ɵ]
[f«ʃ]
[f«z]
[f«v]
[f«s]
[f«k]
[vik]
[fuv]
[geyD]
[zuk]
[fat]
[zut]
[vöp]
[zob]
[dɔT]
[Doyf]
[fID]
[Days]
Method
Participants
The participants were 24 American infants
(14 males and 10 females), approximately 9
months of age, with a mean age of 39 weeks, 6
days (range 5 38 weeks, 2 days to 42 weeks, 1
day). To obtain the 24 infants, it was necessary
to test 25. The additional infant was excluded
due to failure to respond to the lights.
Stimuli
The same female speaker as Experiment 1
recorded the stimuli for this experiment. Once
again, she recorded 16 lists of 12 monosyllabic
nonsense words, all following a CVC pattern.
Eight of the lists (Shared CV lists) contained
repetitions of the initial CV portions of the
items while the remaining lists (Control lists)
contained unrelated foils. The six common
CV’s used in the test lists were [bo], [nu], [vö],
[gI], [f«], and [Dey]. The stimulus lists were
comparable in duration (ranging from 19.9 to
21.1 s) and rms amplitude (72) to those in
Experiment 1. Examples of the Shared CV and
Control lists are displayed in Table 2.
Design, Apparatus, and Procedure
These were identical to those in Experiment 1.
ATTENTION TO SOUND SIMILARITIES
Results and Discussion
As in Experiment 1, mean listening times to
the Shared CV lists and the Control lists were
calculated and averaged for each of the 24 subjects. Across all subjects, the average listening
times were 11.80 s (SD 5 2.85 s) for the Shared
CV lists and 9.86 s (SD 5 3.2 s) for the Control
lists. A paired t test indicated that this difference
in average listening times was statistically significant [t(23) 5 3.665, p 5 .0013]. The same
tendency was observed in the analysis with lists
as a random factor [t(10) 5 3.01, p , .02].
Thus, these results indicate that 9-month-olds
listened significantly longer to lists with an initial shared CV element.
Taken together with the results of Experiment 1, the present results suggest that
9-month-olds are more attentive to sound similarities at the beginnings of syllables than at the
ends of syllables. With respect to their productions of speech at this age, 9-month-olds often
utter CV’s in their babbling. Moreover, they are
approaching the point when they will begin to
utter their first words. Perhaps, then, it is not
surprising that in listening to speech they might
focus on the initial portions of utterances. The
first step for the infant in trying to reproduce
what he or she hears might well be to attempt to
produce the initial portion of the utterance. In
this sense, infants might attend most closely to
the beginnings of utterances.
What is somewhat surprising about the
present results is the kind of unit to which
infants responded, the initial CV of a CVC
syllable. According to the view that the natural
constituents of syllables are onsets and rimes
(Fudge, 1969; Goldsmith, 1990; Selkirk, 1982;
Treiman, 1989), the infants appear to have responded to an ill-formed constituent. However,
it is premature to draw such a conclusion without further information about whether infants
actually were attending to the whole CV or just
to a particular portion of it. Since CV’s by
definition contain both an onset consonant and a
vowel, we need to further clarify the exact focus
of infants’ attention. In the next two experiments, we probed whether infants direct their
attention toward information corresponding to
69
both onsets and vowels or whether information
corresponding to one of these elements is significantly more salient than the other. In Experiment 3, we examine infants’ sensitivity to
shared initial consonants (Alliteration), whereas
in Experiment 4, we investigate their sensitivity
to shared vowels (Assonance).
EXPERIMENT 3
Our first objective was to examine whether
9-month-olds attend to similarities in syllables
involving shared initial consonants. As noted
earlier, infants at this age are close to making
their first attempts at uttering words and engage
in reduplicative babbling in which initial consonant sounds are often repeated in sequences in
utterances (Vihman, 1996). In fact, alliteration
has been observed to occur frequently in soundbased language play by very young children
(Dowker, 1986,1989; Dowker & Pinto, 1993;
Sutton-Smith, 1981; Weir, 1962). There is also
evidence from a variety of sources that suggests
that 9-month-olds are beginning to comprehend
some words (Benedict, 1979; Huttenlocher,
1974) and build a lexicon (Jusczyk, 1997; Jusczyk & Aslin, 1995; Jusczyk & Hohne, 1997).
Although relatively little is known about how
the organization of the lexicon actually develops, there is some reason to believe that the
initial sounds of words are a factor in how
lexical entries are related. For example, the notion that the initial sounds of words play an
important role in recognizing them in fluent
speech figures prominently in some models of
adult word recognition (Cole & Jakimik, 1980;
Marslen-Wilson, 1987, 1990; Marslen-Wilson
& Zwitzerlood, 1989). Hence, it would not be
surprising if the differentiation of syllables into
subsyllabic constituents begins with attention to
the onsets of syllables.
To examine infants’ sensitivity to similarities
in syllable onsets, we created a new set of CVC
materials organized into two types of lists. For
half of these (Alliterative lists), the items within
a list all began with the same initial consonant;
for the other half (Control lists), there was no
shared phonetic property among the items in a
particular list. Once again, we hypothesized that
if infants attend to similarities relating to the
70
JUSCZYK, GOODMAN, AND BAUMANN
initial consonants of the items in the lists, they
should listen significantly longer to the Alliterative than to the Control lists. However, even if
9-month-olds are sensitive to similarities in the
onsets of the syllables in the Alliterative lists,
there are several reasons why these similarities
may be more difficult to detect with the present
materials than those used in the previous experiment. The first reason has to do with the fact
that the CVC’s in Shared CV lists in Experiment 2 have more shared material than do the
CVC’s in the Alliterative lists. Of course, the
import of this fact depends on the extent to
which the infants really attend to information
corresponding to shared vowels. The second,
and perhaps more important, reason why the
similarities may be harder to detect in the
present experiment has to do with variability in
the acoustic realization of the initial consonants.
Because the following vowel context for the
items in a Shared CV list was always the same,
variability in the production of the initial consonant was minimized. By contrast, the vowel
context for the items in the Alliterative lists
were varied. Consequently, owing to the effects
of coarticulation, there is much greater acoustic
variability in the production of the initial consonants (Liberman, Cooper, Shankweiler, &
Studdert-Kennedy, 1967), which may influence
whether infants perceive them to be similar.
Method
Participants
The participants were 24 American infants
(12 males and 12 females), approximately 9
months of age, with a mean age of 38 weeks
(range 5 36 weeks, 5 days to 40 weeks, 5 days).
To obtain the 24 subjects, it was necessary to
test 27. Infants were excluded for the following
reasons: crying (2) and experimenter error (1).
Stimuli
Once again, 16 lists of 12 monosyllabic nonsense words, all following a CVC pattern, were
used. Eight of these (Alliterative lists) contained
repetitions of syllable onsets (C), whereas the
remaining ones (Control lists) contained unrelated foils. The shared consonants for the 6 test
TABLE 3
Examples of Alliterative and Control Lists
Alliterative list
Control list
[mod]
[mib]
[mön]
[mug]
[mɔf]
[mIʃ]
[m«ɵ]
[mat]
[mæD]
[mayz]
[mɔl]
[m«T]
[p«b]
[ɵÅg]
[geyD]
[kuv]
[Tod]
[fæɵ]
[lID]
[goyl]
[hin]
[wæt]
[beyz]
[Dayk]
lists were [f], [l], [g], [h], [w], and [R]. The
stimulus lists were comparable in duration
(ranging from 20.0 to 21.7 s) and rms amplitude
(72) to those in the previous experiments. Examples of the Alliterative and Control lists are
shown in Table 3.
Design, Apparatus, and Procedure
These were identical to the previous experiments.
Results and Discussion
Once again, mean listening times to the 2 list
types were calculated for each infant across the
12 test lists. The mean listening times were
averaged for lists containing repetition of CV as
well as the Control lists. Across all subjects, the
average listening times were 11.68 s (SD 5
3.11 s) for the Alliterative lists and 10.07 s
(SD 5 3.18 s) for the Control lists. A paired t
test indicated that this difference in average
listening times was statistically significant
[t(23) 5 3.043, p 5 .0058]. The same tendency
was evident in the analysis with lists as a random factor [t(10) 5 2.22, p 5 .05]. Thus, infants listened significantly longer to Alliterative
than to the Control lists, implying that they are
sensitive to the similarities in the onsets of
syllables.
The present findings parallel those of Experiment 2 in which 9-month-olds attended longer
to lists which contained shared CV’s. However,
71
ATTENTION TO SOUND SIMILARITIES
in contrast to Experiment 2, the vowel context
was varied for the items within each Alliterative
list. This suggests the presence of information
corresponding to shared vowel nuclei is not
necessary in order for 9-month-olds’ to attend to
similarities in syllable onsets. The next question
is whether infants at this age will also give
evidence of attending to similarities involving
only the vocalic portions of syllables.
EXPERIMENT 4
Given how infants responded to the rhyming
lists in Experiment 1, there is reason to believe
that infants may not respond to similarities relating to the vowels of CVC syllables. Nevertheless, findings from a number of speech perception studies suggest vowel information is
very salient for infants. For example, Kuhl’s
early studies (Kuhl, 1979, 1983) showed that
6-month-olds are able to generalize across differences in pitch contour and speakers’ voices
in discriminating certain vowel contrasts. In this
respect, infants appear to have some perceptual
constancy with respect to vowels. Furthermore,
on the basis of her more recent investigations
exploring the internal organization of vowel
categories, Kuhl has argued that 6-month-olds’
vowel categories are organized around prototypes similar to those of adult speakers of the
native language (Grieser & Kuhl, 1989; Kuhl,
1991; Kuhl et al., 1992). There has also been
some suggestion that declines in sensitivity to
nonnative language vowel categories may occur
earlier than for consonants (Polka & Werker,
1994). However, more recent research has
raised questions about the interpretation of the
asymmetries observed in infants’ discrimination
of nonnative vowel contrasts (Polka & Bohn,
1996). In particular, Polka and Bohn have suggested that these asymmetries are more likely
the result of language-universal tendencies than
language-specific influences on perception.
Regardless of whether vowels actually undergo an earlier language-specific reorganization than consonants, infants are sensitive to
information in vowels from an early age (Swoboda, Kass, Morse, & Leavitt, 1978; Swoboda,
Morse, & Leavitt, 1976; Trehub, 1973). The
aim of the present experiment was to determine
whether 9-month-olds attend to similarities involving vowels of CVC syllables. For this purpose, we created a new set of CVC materials
organized into two types of lists. For half of
these (Assonance lists), the items within a list
all contained the same vowel; for the other half
(Control lists), there was no shared phonetic
property among the items in a particular list.
Once again, we hypothesized that if infants attend to similarities involving the vowels of the
items in the lists, they should display significantly longer listening times for the Assonance
than for the Control lists.
Method
Participants
The participants were 24 American infants
(15 males and 9 females), approximately 9
months of age, with a mean age of 38 weeks 6
days (range 5 37 weeks, 2 days to 41 weeks, 2
days). One additional infant was tested but not
included due to experimenter error.
Stimuli
Once again, 16 lists of 12 monosyllabic nonsense words, all following a CVC pattern, were
used. Eight of these (Assonance lists) contained
items that shared the same vowels (V), whereas
the remaining ones (Control lists) contained unrelated foils. The shared vowels for the 6 test
lists were [u], [ey], [a], [o], [«], and [æ]. The
stimulus lists were comparable in duration
(ranging from 20.4 to 22.4 s) and rms amplitude
(72) to those in the other experiments. Examples of the Assonance and Control lists are
shown in Table 4.
Design, Apparatus, and Procedure
These were identical to those in the previous
experiments.
Results and Discussion
As before, mean listening times to the Assonance and Control lists were calculated for each
of the 24 subjects. Across all subjects, the average listening times were 10.76 s (SD 5 3.18 s)
for the Assonance lists and 10.11 s (SD 5
2.66 s) for the Control lists. A paired t test
72
JUSCZYK, GOODMAN, AND BAUMANN
TABLE 4
Examples of Assonance and Control Lists
Assonance list
Control list
[nId]
[DIT]
[dIn]
[bIs]
[tIz]
[kID]
[ʃIÍ]
[pIT]
[gIp]
[mIg]
[zIk]
[sIb]
[p«ʃ]
[Tæg]
[zok]
[dit]
[tayn]
[göb]
[vad]
[Doym]
[seyt]
[nuD]
[kɔp]
[ʃ«z]
indicated that this difference in average listening times was not statistically significant [t(23)
5 1.32, p , .20]. The lack of a significant
assonance effect was also evident in an analysis
with lists as a random factor [t(10) 5 0.48, p .
.60]. Thus, there is no indication that 9-montholds listen significantly longer to the lists that
share only a common vowel nucleus.
When coupled with the results of Experiment
3, the present results suggest that the presence
of a common vowel nucleus is neither a necessary nor a sufficient condition for infants to
attend to similarities in different syllables. In
fact, the results thus far indicate that 9-montholds only exhibit listening preferences for syllables with common elements when these include common onsets. To provide further
statistical confirmation of this observation, we
performed a one-way ANOVA on the difference scores (average listening times for Experimental lists 2 average listening times for Control lists) from the first four experiments. A
significant main effect was observed for Syllable Structure Type [F(3,92) 5 3.374, p , .05].
A series of contrast tests based on the ANOVA
was carried out to explore possible differences
among the listening times to the four-syllable
structure types. The first comparison indicated
that the materials with common onsets (i.e., the
Alliterative and the Shared CV Lists) differed
significantly [F(3,92) 5 8.84, p , .005] from
those without common onsets (i.e., the Rhym-
ing and the Assonance lists). The second comparison examined whether the listening preferences for materials with common onsets were
greater when a common vowel nucleus was also
present (i.e., Shared CV lists) than when it was
absent (Alliterative lists). This difference was
not significant [F(3,92) , 1.00], suggesting that
any contribution from the presence of a common vowel nucleus was negligible in accounting for the infants’ preferences for the Shared
CV lists. To return to a point discussed in conjunction with the results of Experiment 2, it
appears that the infants in that experiment may
have been responding more to similarities
which they perceived at the beginnings of syllables than to both the onsets and vowel nuclei.
Thus, the infants’ preferences for the Shared
CV lists are not at odds with the view that the
natural constituents of the syllable are the onset
and rime. Rather, the findings from Experiments 2 are consistent with the view that
9-month-olds attend to intrasyllabic information
that corresponds to at least one of these types of
constituents, viz., onsets.
There are several ways to interpret the findings thus far. On the one hand, the fact that
infants find certain kinds of information within
the syllable to be especially salient does not
necessarily imply that they break down or organize the syllable in line with this salient
source. The saliency of the component could
simply render the syllable as a whole as similar
to other whole syllables that contain the same
intrasyllabic information. Attending to such
similarities may be a prerequisite for, but not
necessarily equivalent to, perceiving internal
constituents of syllables. On the other hand, it is
possible that our findings are an indication that
9-month-olds are actually beginning to segment
phonetic units from syllables. In other words,
not only might the infants have detected some
similarity in the onsets of syllables but they may
also have detected that these begin with the
same initial consonant. However, before we can
accept the latter conclusion, there is another
possibility that must be ruled out. Namely,
9-month-olds may not have extracted information about the initial consonants of the syllables,
but some more general property about the initial
73
ATTENTION TO SOUND SIMILARITIES
portions of syllables.2 For example, within either a Shared CV or an Alliterative list, the
items not only begin with the same initial consonant, but the manner in which they begin is
similar. For example, CVC’s beginning with [b]
will also have an abrupt onset, as opposed to
items beginning with [w], which will have a
more gradual build-up of acoustic energy. The
next experiment was designed to determine the
nature of the information to which the 9-montholds are responding.
EXPERIMENT 5
The only way to determine whether 9-montholds are responding to general characteristics of
the beginnings of syllables or to the inclusion of
common initial consonant segments is to create
lists in which these two properties are unconfounded. The solution is to choose items which
do not start with the same initial consonant, but
which begin with the same manner of articulation (e.g., all the items begin with a voiced stop,
but they do not all begin with the same voiced
stop). If 9-month-olds are simply focused on the
manner in which syllables begin, then they still
should listen significantly longer to these kinds
of lists than they do to control lists. However, if
infants’ listening preferences are attributable to
their detection of a common initial consonant in
the syllables, then such preferences may not
occur for lists in which the initial consonants
share manner of articulation features but are not
identical.
Method
Participants
The participants were 24 American infants
(14 males and 10 females), approximately 9
months of age, with a mean age of 39 weeks, 5
days (range 5 36 weeks, 6 days to 42 weeks, 1
day). Three additional infants were tested but
not included due to fussiness.
Stimuli
Once again, 16 lists of 12 monosyllabic nonsense words, all following a CVC pattern, were
2
We thank Anne Cutler for calling this possibility to our
attention.
TABLE 5
Examples of Common Manner and Control Lists
Common Manner list
Control list
[deyD]
[gIp]
[böT]
[dot]
[göɵ]
[dög]
[g«ʃ]
[bIv]
[gayk]
[bIm]
[dæs]
[baz]
[wös]
[mæt]
[sayb]
[tIɵ]
[ɵIv]
[Döm]
[zeyl]
[j«z]
[Tuk]
[hon]
[ɵæD]
[vIʃ]
used. Eight of these (Common Manner lists)
contained items whose initial consonants came
from the same manner of articulation class,
whereas the remaining ones (Control lists) contained unrelated foils. The shared manner
groups for the 6 test lists were affricates ([D],
[č]), liquids ([l], [r]), voiceless fricatives ([f],
[ʃ], [ɵ]), voiced stops ([b], [d], [g]), voiced
fricatives ([z], [v], [R]), and voiceless stops ([p],
[t], [k]). Within a particular Common Manner
list, each of the consonants occurred equally
often as a syllable onset. The stimulus lists were
comparable in duration (ranging from 20.0 to
21.0 s) and rms amplitude (72) to those in the
other experiments. Examples of the Common
Manner and Control lists are shown in Table 5.
Design, Apparatus, and Procedure
These were identical to those in the previous
experiments.
Results and Discussion
As in the previous experiments, mean listening times to the Common Manner and Control
lists were calculated for each of the 24 subjects.
Across all subjects, the average listening times
were 10.64 s (SD 5 2.39 s) for the Common
Manner lists and 9.23 s (SD 5 2.55 s) for the
Control lists. A paired t test indicated that this
difference in average listening times was statistically significant [t(23) 5 3.17, p 5 .0043].
The preference for the Common Manner items
74
JUSCZYK, GOODMAN, AND BAUMANN
was in the same direction in the analysis with
lists as a random factor, although only marginally significant [t(10) 5 1.98, p , .08]. Furthermore, with respect to the Common Manner lists,
there was no indication that infants responded
differently to the lists in which there were six
repetitions of a consonant versus those in which
there were four repetitions. Thus, the present
results indicate that 9-month-olds show significant listening preferences for lists in which the
syllable onsets begin with a similar manner of
articulation. It is interesting that the magnitude
of the effect in the present experiment was
about the same as for the Alliterative lists in
Experiment 3. Thus, 9-month-olds attend to
similarities in the manner of syllable onsets,
even when the initial consonants differ from
each other.
Hence, we cannot rule out the possibility that
infants in Experiment 3 responded to commonalties in manner of syllable onsets, as opposed
to extracting a common initial phoneme from
the items in the Alliteration lists. However,
there is another possible explanation for the
result of the present experiment. Although it is
true that the items on a Common Manner list did
not all begin with the same consonant, there
were between four (as in the case of the voiced
stops [b], [d], [g]) and six (as in the case of the
liquids [r] and [l]) items on each list that did
have a common consonant onset. Perhaps infants detected the fact that one of these consonants recurred as the onset of some of the syllables in the list. If so, they might have been
responding to this feature of the lists rather than
to the fact that all of the items on the list shared
the same manner of syllable onset. We decided
to investigate this possibility in the following
experiment.
EXPERIMENT 6
If infants in the previous experiment listened
longer to the Common Manner lists not because
they perceived the similarities in the manner of
syllable onsets, but because they detected the
recurrence of some initial consonant segments
in the lists, then varying the manner of syllable
onsets in a list should have no effect on their
preferences provided that some items on the list
contain the same initial consonant. To test this
possibility, we created new experimental lists
from the ones used in the previous experiment.
In each new list, we retained CVC’s beginning
with one of the consonants from each manner
class and replaced the other CVC’s with new
ones from other manner of articulation classes.
Consequently, although some of the items in a
given list began with the same phonetic segment, there was no shared manner feature
across all the items in the list. If the infants in
the previous experiment were simply reacting to
the recurrence of a particular initial phonetic
segment in the lists, then a similar listening
preference should be obtained for the new lists
versus control lists in the present experiment.
Method
Participants
The participants were 24 American infants
(12 males and 12 females), approximately 9
months of age, with a mean age of 40 weeks, 0
days (range 5 37 weeks, 5 days to 42 weeks, 0
days). Four additional infants were tested but
not included due to fussiness (1), parental interference (2), and failure to look at the flashing
lights (1).
Stimuli
Once again, 16 lists of 12 monosyllabic nonsense words, all following a CVC pattern, were
used. Eight of these (Repeated Consonant lists)
contained several items that shared the same
initial consonant, whereas the remaining ones
(Control lists) contained unrelated foils. A different consonant was repeated in each of the 6
test lists. The consonants used were [dz], [r], [f],
[d], [z], and [p]. These consonants were selected
because they occurred on the Common Manner
lists of Experiment 5 and they represented a
wide range of the English consonant space. The
frequency with which a particular consonant
recurred as a syllable onset was equivalent to its
occurrence in the lists in the previous experiment. Hence, [D] and [r] each occurred in six
items on their respective lists, whereas the remaining consonants occurred in four items on
their respective lists. The positions of the recur-
ATTENTION TO SOUND SIMILARITIES
TABLE 6
Examples of Repeated Consonant and Control Lists
Repeated consonant list
Control list
[deyD]
[zIp]
[föT]
[dot]
[löɵ]
[döf]
[D«ʃ]
[mIv]
[jayk]
[pIm]
[dæs]
[naz]
[hayD]
[bIʃ]
[TId]
[w«p]
[mayf]
[Dæl]
[föb]
[dɔn]
[zæb]
[pug]
[k«T]
[gom]
ring consonant items in the lists were the same
as in the previous experiment. Thus if items
beginning with [f] had occurred in the 1st, 5th,
8th, and 10th positions on the Common Manner
lists, they occurred in the same positions on the
Repeated Consonant lists. The stimulus lists
ranged in duration from 20.0 to 26.2 s and had
an average rms amplitude of 72. Examples of
the Repeated Consonant and Control lists are
shown in Table 6.
Design, Apparatus, and Procedure
These were identical to those in the previous
experiments.
Results and Discussion
As in the previous experiments, mean listening times to the Repeated Consonant and Control lists were calculated for each of the 24
subjects. Across all subjects, the average listening times were 9.45 s (SD 5 2.89 s) for the
Repeated Consonant lists and 8.81 s (SD 5
3.48 s) for the Control lists. A paired t test
indicated that this difference in average listening times was not statistically significant [t(23)
5 0.88, p . .35]. Also, in the analysis with lists
as a random factor, the Repeated Consonant
lists did not differ significantly from the Control
lists [t(10) 5 1.28, p . .20]. Again, there was
no indication that the lists with six repetitions of
an item were responded to differently from
those with four repetitions of an item. Thus, in
75
the absence of a shared manner of syllable onset
among the items in the lists, the 9-month-olds
showed no significant listening preferences for
lists which included some items with the same
initial consonant.
However, a potential criticism of the present
control experiment is that only one consonant
was repeated in each list, whereas in Experiment 5, two or three consonants were repeated
in each of the Common Manner lists. It is certainly possible that having several different, albeit unrelated consonants, repeat in a list would
be sufficient to induce a preference for these
lists over lists of items with nonrepeating consonants. In designing the present experiment,
our goal was to use lists in which a consonant
from each of the Common Manner lists in Experiment 5 was used with the same frequency
and positioning as in the earlier study. Although
we cannot be certain whether infants might
show a preference for lists with multiple, repeating, but unrelated, consonants, we consider
this possibility to be unlikely.
The present findings are consistent with the
view that 9-month-olds in Experiment 5 were
responding to perceived similarities in the manner in which syllables in the Common Manner
lists began. The fact that infants may be attentive to manner of articulation at syllable onsets
is perhaps not surprising. As Stevens (1996; p.
1693) has noted, “the acoustic signal provides a
direct indication that a stop consonant is released or that a consonant is an obstruent or a
sonorant, or that a syllable nucleus occurs.”
Thus, there are well-defined acoustic correlates
for manner of articulation (Stevens, 1994). In
addition, under noisy conditions information
about manner of articulation is better preserved
than that for either voicing or place of articulation (Miller & Nicely, 1955; Wang & Bilger,
1973). Moreover, adult listeners tend to sort
phonemes first according to manner, then voicing, and subsequently place of articulation (Peters, 1963). Hence, there is evidence that information about manner of articulation is robustly
present in the speech signal. Furthermore,
9-month-olds appear to be sensitive to this kind
of information, at least when it occurs at the
onsets of syllables. The next question to be
76
JUSCZYK, GOODMAN, AND BAUMANN
addressed is whether infants at this age might
show a similar sensitivity to information about
other kinds of phonetic dimensions.
TABLE 7
Examples of Common Place and Control Lists
Common Place list
Control list
[beyD]
[muT]
[bip]
[pok]
[bug]
[payk]
[m«ʃ]
[puɵ]
[miv]
[bIm]
[mæs]
[paÚ]
[wös]
[mat]
[sayb]
[liɵ]
[ɵIv]
[Döm]
[zeyl]
[j«z]
[Tuk]
[hon]
[ɵæD]
[vIʃ]
EXPERIMENT 7
Stevens (1994) postulates a hierarchical organization with respect to the acoustic and articulatory correlates of distinctive features such
that the identification of some features for a
segment (e.g., those relating to place of articulation) is facilitated if other features (e.g., ones
relating to manner of articulation) are known.
He suggests that an optimum strategy for speech
recognition is to identify features according to
that particular order. The results of Experiment
5 suggest that 9-month-olds are attentive to the
kinds of features at the top of this hierarchy, i.e.,
ones relating to manner of articulation. The
present experiment was designed to test whether
they are also attentive to the kinds of features
that are considered to be farther down in the
hierarchy, viz., those which relate to the place
of articulation of a segment. Consequently, we
constructed a new set of CVC’s to create a
series of lists (Common Place) in which the
initial consonants were varied but shared the
same place of articulation feature. If 9-montholds detect that the CVC’s in these lists begin
with the same place of articulation, they should
listen longer to these types of lists than to ones
containing unrelated CVC’s.
whereas the remaining ones (Control lists) contained unrelated foils. The shared place groups
for the 6 test lists were bilabials ([b], [p], [m]),
dentals ([f], [v], [ɵ]), aveolars ([t], [r], [n]),
alveolars ([s], [d], [l]), palatals ([D], [ʃ], [j]),
and velars ([w], [g], [k]). Within a particular
Common Place list, each of the consonants occurred equally often as a syllable onset. The
stimulus lists were comparable in duration
(ranging from 20.0 to 21.8 s) and rms amplitude
(72) to those in the other experiments. Examples of the Common Place and Control lists are
shown in Table 7.
Design, Apparatus, and Procedure
Method
These were identical to those in the previous
experiments.
The participants were 24 American infants
(14 males and 10 females), approximately 9
months of age, with a mean age of 39 weeks, 4
days (range 5 37 weeks, 1 day to 41 weeks, 5
days). Four additional infants were tested but
not included due to crying (1) and failure to
attend to the flashing lights (3).
Results and Discussion
Participants
Stimuli
Once again, 16 lists of 12 monosyllabic nonsense words, all following a CVC pattern, were
used. Eight of these (Common Place lists) contained items whose initial consonants came
from the same place of articulation class,
As in the previous experiments, mean listening times to the Common Place and Control lists
were calculated for each of the 24 subjects.
Across all subjects, the average listening times
were 9.17 s (SD 5 2.50 s) for the Common
Place lists and 9.20 s (SD 5 3.44 s) for the
Control lists. A paired t test indicated that this
difference in average listening times was not
statistically significant [t(23) 5 0.052, p . .95].
Similarly, the absence of a significant effect for
Common Place also occurred in the analysis
with lists as a random factor [t(10) 5 .06, p .
.95]. Consequently, there was no indication that
ATTENTION TO SOUND SIMILARITIES
the infants responded to the presence of the
shared place of articulation feature in the onsets
of the items in the Common Place lists.
One interesting implication of the present
results is that that they bolster the argument that
infants in Experiment 5 were not simply responding to repeated consonants, but to some
perceived similarity among the onsets of items
in the Common Manner lists. The Common
Place lists in the present experiment also contained three different repeating consonants (as
did four of the six Common Manner lists). Yet,
the presence of repeated consonants did not lead
to significantly longer listening times for the
Common Place than for the Control lists. This
finding resolves the uncertainty raised in the
discussion of Experiment 6 as to whether infants might show a preference for any lists that
included multiple, repeated initial consonants.
To explore further differences in how infants
responded to the Common Manner and Common Place lists, we performed an ANOVA of a
mixed 2 (Experiment) 3 2 (List Type) design
on the data from Experiments 5 and 7. The
critical interaction between Experiment and List
Type was marginally significant [F(1,46) 5
3.48, p 5 .068] in the analysis by subjects,
although not in the analysis with lists as a random factors [F(1,10) 5 1,83, p 5 .20]3. Thus,
there is some additional support for the claim
that infants responded differently to the Common Manner lists in Experiment 5 than they did
to the Common Place lists in the present experiment. One possible interpretation of this difference is that place of articulation features are
simply less salient for 9-month-olds than are
manner of articulation features. This explanation certainly accords with the observations
from experiments with adults showing that
manner features are better preserved under
noisy listening conditions (Miller & Nicely,
1955; Wang & Bilger, 1973) and are the primary ones chosen to group speech sounds into
categories (Peters, 1963; Shepard, 1972). In any
case, the pattern of results with infants is cer3
Again, note that because of the small number of lists in
each experiment, the degrees of freedom are few. Hence, the
sensitivity for the analyses by lists is not great.
77
tainly compatible with the view that the identification of place of articulation information may
depend on prior identification of information
relating to manner of articulation, as Stevens
(1994) has proposed. Perhaps the dependence is
one that applies not only in on-line speech perception, but also in ontogenetic development.
GENERAL DISCUSSION
The present series of experiments was undertaken to explore 9-month-olds’ sensitivity to
intrasyllabic constituents. The results suggest
that infants at this age are most attentive to
information at the beginning of syllables. Significant listening preferences for the experimental lists occurred when the common property
consisted of shared CV’s, shared initial C’s, or
a common manner of articulation for the initial
C of the list items. In contrast, listening preferences for the experimental lists did not occur
when the common property involved either a
shared rime (VC) or a shared vowel nucleus
(V). Finally, the one instance in which infants
did not respond to a common property at the
beginning of the syllables in the experimental
lists involved the same place of articulation.
As noted earlier, linguists have postulated
that the natural constituents of syllables are
onsets and rimes (Fudge, 1969; Goldsmith,
1990; Kenstowicz, 1994; Selkirk, 1982). Moreover, there are data to suggest that these constituents are psychologically real for adults
(Treiman, 1983, 1986; Treiman & Danis, 1988;
Treiman et al., 1994) and preschool-age children (Treiman, 1985, 1992, 1995). The present
results suggest that 9-month-olds have not fully
differentiated these kinds of subsyllabic constituents. On the one hand, there is no indication
that the 9-month-olds are sensitive to similarities among rimes. On the other hand, infants at
this age do respond to similarities that corresponded to the syllable onsets of the test materials. The latter finding could be an indication
that infants are beginning to discover intrasyllabic constituents and that this process starts
with a focus on onsets. Presumably, at some
later point in development, they turn their attention to the rime constituents. However, this conclusion must be tempered in two respects. First,
78
JUSCZYK, GOODMAN, AND BAUMANN
the findings for the Common Manner lists show
that 9-month-olds attend to the manner in which
syllables begin, even when there is variation in
the identity of the initial segments. Thus, we
cannot say with certainty whether infants have
actually extracted an onset constituent from the
syllable or whether they are responding to some
more general acoustic similarities that they perceive about the way that the syllables begin.
Second, because only CVC items were included
in the present study, we cannot separate the
possibility that infants were responding to similarities corresponding to the onset constituent
of syllables from one in which they were responding to similarities corresponding to the
initial consonants of the items. Only a further
study using items with initial consonant clusters
will allow us to separate these two possibilities.
What is evident in the present results is that
the attention of these English-learning 9-montholds appears to be directed to the beginnings of
syllables rather than to the endings. It is possible that attention to the beginnings of syllables
in perceiving speech is a consequence of
changes taking place in other domains of language acquisition. For instance, the age of the
present subjects corresponds to the earliest age
for which some comprehension of words has
been noted (Benedict, 1979; Huttenlocher,
1974). Thus, attention to the way words begin
may go hand in hand with developing a lexicon
for the native language. Also, infants at this age
are beginning to segment words from fluent
speech (Echols et al., 1997; Jusczyk & Aslin,
1995; Morgan & Saffran, 1995; Saffran et al.,
1996). Focusing on the beginnings of utterances
could provide information about certain properties of word onsets (e.g., allophonic and phonotactic cues). Finally, important changes are also
occurring in speech production capacities at
around this age. Infants’ babbling patterns become more complex (Koopmans van Beinum &
van der Stelt, 1986; Oller, 1980; Roug et al.,
1989) and come to more closely resemble the
sound patterns of the native language (BoyssonBardies, Sagart, & Durand, 1984; Boysson-Bardies, Sagart, Halle, & Durand, 1986; BoyssonBardies & Vihman, 1991; Boysson-Bardies et
al., 1992). A tendency to focus on the begin-
nings of utterances so that one can sequence
articulatory gestures properly may be important
in trying to imitate speech input and to produce
one’s first words.
As noted earlier, many psycholinguists have
commented on the fact that endings of utterances are particularly important for learners
during early phases of language acquisition
(Blasdell & Jensen, 1970; Echols & Newport,
1992; Peters, 1983; Slobin, 1973). In this respect, the present findings are somewhat unexpected. Still, two points are worth considering.
First, some of the same researchers have also
commented on the importance of the beginnings
of utterances for learners (Peters, 1985; Slobin,
1973). Second, as discussed in conjunction with
the findings from Experiment 1, the importance
of attention to endings of utterances usually
comes up in discussions of how infants (considerably older than the ones tested here) acquire
morphology. Sensitivity to morphological endings may not be the same as sensitivity to the
endings of monosyllables.
It is also possible that if older infants were
tested on the same types of materials, they
might well exhibit preferences for lists with
common rimes. However, the results of a follow-up investigation that we recently conducted
found no evidence that either 14- or 18-montholds attend to the rime lists (Goodman, Jusczyk,
& Bauman, in press). One possibility is that
attention to final portions of syllables develops
at some point after the discovery of morphology. Hence, attention to endings may be heightened by learning enough lexically related items
to notice that there are discrepancies in meanings between items with the same roots, but
different inflections. Alternatively, attention to
endings may be evident only with utterances
longer than the CVC’s used in the present study.
For example, many, but not all, English suffixes
append additional syllables to root morphemes.
It is conceivable that attention to these develops
prior to attention to material that is contained
entirely within the final portion of a single syllable. Finally, it would be worthwhile to explore
how attention to endings develops for infants
who are exposed to languages that are much
more highly inflected than English. It is possible
ATTENTION TO SOUND SIMILARITIES
that a greater frequency of recurring suffixes
may drive the language learner to focus more on
endings.
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(Received August 12, 1997)
(Revision received July 21, 1998)