Poster group
Details of individual items:
poster
Two experiments using different procedures were performed in which newborns'ability to process information about object shape with their hands wasexplored. In the first experiment, subjects were 45 full-term newborns (meanage 42.25 hour old). A haptic fixed-trial procedure was used in whichnewborns were presented with a small object (a wooden cylinder) during ninetrials. Twenty-four newborns (12 boys and 12 girls) were tested with theirleft hand and 21 newborns (9 boys and 12 girls) with their right hand.Results showed a decrease in holding times for both right and left handsduring the nine trials allotted. The duration of the last two trials wassignificantly lower than the duration of the first two trials (for the righthand, t(20) 3.25 ; p .004 and for the left hand, t(23) 2.02 ; p.054). However haptic habituation was an ambiguous behaviour: it can eitherbe interpreted as an evidence of information processing or motor fatigue. A second experiment was then performed to provide clearer evidence forhaptic habituation and discrimination in newborns. An infant-controlhabituation procedure with a partial-lag design was used. Twenty-fourhealthy full-term newborns (10 girls and 14 boys ; mean age 44.6 hours).Two small wooden objects with different shapes were used (a cylinder and aprism). Half of the 24 infants received a haptic habituation sequence withtheir right hand and the other half with their left one. In each group (12newborns), half of the infants were randomly assigned to a lag conditionduring which they received two postcriterion trials (lag trials) with thefamiliar stimulus before receiving the novel stimulus on postcriteriontrials. The other half (non lag) were presented with the novel stimulusimmediately following criterion. Haptic habituation was found both for rightand left hands in about 6 to 7 trials. This result supported that ofexperiment 1. Discrimination was also evidenced both for right and lefthands (respectively, t(11) 3.35 ; p .006 and t(11) 3.19 ; p .008).These results showed that neonates are able to process and encode someinformation about object shape and then to discriminate between differentshapes. It is the first evidence of such ability in neonates. Methodologicalprocedure, haptic perception and memory with regard to sensory symmetry arediscussed and developmental perspectives are proposed.
poster
OBJECTIVES: The present study examined 1) newborns' haptic-tactualexploration of weight using an habituation/dishabituation paradigm and 2)the effects of maternal depression on infants' perceptual performance.PARTICIPANTS: Forty-four fullterm newborns (M age 44.5 hours) wererecruited at a county hospital's newborn nursery. Inclusion criteriaincluded: > 37 weeks gestation, no medical complication or illness, Apgarscores of 7 or greater at one and five minutes and no physiological orphysical anomalies. The mothers were administered the Center forEpidemiological Studies - Depression Scale (CES-D), a 20-item scale thatmeasures depressive symptoms. Infants whose mothers scored 16 or higher onthe CES-D (cutpoint for depressive symptoms) were assigned to the depressedgroup (n26), M CES-D 24.0, SD 7.2 and those who scored between 3 and 12were assigned to the non-depressed group (n22), M CES-D 9.3, SD 2.4.PROCEDURE: Testing always occurred between feedings and when the infant wasin a quiet alert state. The newborn was unswaddled and placed supine in thehospital bassinet. The bassinet was tilted to a 45 degree angle. A small,heavy (20 gms) tube or a light-weight tube (5 gms) was placed in theinfant's right hand. Half of the infants in each group were habituated withthe heavy tube and the other half to the light tube. Observers blind to thehypothesis or the mother's depressed score recorded seconds of holding andcoded infant's exploration style. An 'active' code was assigned if theinfant moved the hand with the tube from side to side or attempted totransfer the object to the mouth. A 'passive' code was assigned if theinfant's hand remained still throughout the entire trial. Each trial startedwith the infant's first grasp of the tube and ended when the infant droppedthe tube or after 60 seconds had elapsed. The same weight tube was replacedin the infant's hand until an habituation criterion was met. Seconds ofholding on the first two trials were averaged and served as baseline. Thehabituation criterion was met when on two consecutive trials, seconds ofholding was less than 50% of baseline. Following habituation, the infantreceived two post-habituation trials, identical to the habituation trialsand two test trials with the alternate/novel weight. RESULTS: The two groupsdid not differ on birthweight, gestational age, postnatal complicationsscore, maternal age, or socioeconomic status, but did differ on CES-Dscores, as expected, t (42) 8.26, p < .01. Preliminary analyses revealedthat the variances were not equal and the data did not conform to theassumptions underlying the F distribution. Subsequently, non-parametrictests were conducted. Both groups discriminated the weights, but only whenpresented with the heavy weight first (depressed Wilcoxon Signed Ranks,4.86, p < .05; non-depressed Wilcoxon, 3.68, p < .05). Infants of depressedmothers, however, were coded as more passive in haptic exploration, X2 7.48, p < .01. CONCLUSIONS: These findings reveal that newborn infantsdiscern by haptic touch a change in an object's weight from heavy to light.That newborn infants of depressed mothers show more passive haptic touchexploration of objects supports previous findings that they are lessexploratory.
poster
What kinds of acoustic information specify the meaning of vocal expressions for infants? We are addressing this question by examining infants' intermodal matching of facial and vocal expressions in situations where the pitch of a vocal expression is manipulated. Young infants look preferentially to a facial expression when it is accompanied by its characteristic, emotionally matched vocal expression in an intermodal preference procedure. Infants of 7 months look proportionately longer at a sound-matched happy, sad, angry, or neutral expression when it is presented simultaneously with another facial expression. Infants as young as 3.5 months look longer to their mothers' sad and happy facial expressions when these are accompanied by her sad or happy vocal expression. We are exploiting infants' tendency to look longer at a sound-matched facial expression to test their ability to discriminate vocal expressions and to determine what acoustic information specifies the emotion to them. Seven-month-old infants are presented two facial expressions (sad and happy) side-by-side along with a single sad or happy vocal expression. Infants' looking times to each facial expression are recorded. Following this presentation, infants are given a second presentation in which the perceived pitch of the voice is altered. One group of infants hears a sad vocal expression on the first presentation, followed by a second presentation in which the pitch has been transformed so that it is equivalent to the average fundamental frequency of the happy voice. Another group of infants hears a happy vocal expression on the first presentation, followed by a second presentation on which the average fundamental frequency of the happy voice is decreased to be equivalent to that of the sad voice. A final group sees both facial expressions accompanied by the same vocal expression over both presentations to analyze for order effects. The facial and vocal expressions are synchronized with one another throughout. Twenty (of 32) infants have been tested. Several alternative findings are possible. Infants may continue to look preferentially at a facial expression that is accompanied by its characteristic vocal expression despite the pitch manipulation. For example, an infant might look longer at the happy facial expression on the first presentation and continue to gaze longer at the happy facial expression on the second presentation even though the pitch of the vocal expression has been lowered. Alternatively, infants may shift looking to the other facial expression because the pitch information is more consonant with that facial expression. That is, an infant who looks longer to a happy facial expression when hearing the happy vocal expression on the first presentation may look longer to the sad facial expression once the pitch is lowered. Finally, infants may not show a looking preference because the acoustic information does not specify a particular facial expression. The data obtained will address questions about what acoustic information is pivotal for the discrimination and recognition of expressions.
poster
Most perceptual events are multimodally represented and temporally distributed. One of the basic attributes that defines a temporally distributed multimodal event is duration. To determine how infants respond to such a fundamental feature of their perceptual world, we studied 4, 6, 8, and 10-month-old infants' response to multimodal duration by investigating response to audio/visual syllables differing in duration. The syllables were recordings of either a female or a male actor reciting the syllable /ba/ either for 800, 1300, or 1800 ms. Using an infant-controlled habituation/test procedure, half the infants at each age first were habituated to an 800 ms. syllable (total n = 31) whereas the other half of the infants were habituated to an 1800 ms. syllable (total n = 24) spoken either by a male or female. Each infant controlled the presentation of the syllable by looking at a monitor at which time they could see and hear the actor uttering the syllable every 3 s. for up to a maximum of 32 s. Once the infant met a habituation criterion, 4 kinds of test trials were given. Three of these were trials during which the infant saw and heard the /ba/ syllable at a duration of 800, 1300, or 1800 ms., respectively. The fourth test trial involved presenting a novel syllable (/sha/) at the familiar duration. For those infants who were habituated to the 800 ms. syllable, the 800 ms. test trial syllable served as the familiar (F) test trial whereas for those habituated to the 1800 ms. syllable the 1800 ms. test trial syllable served as the F test trial. The amount of looking during the F test trial served as a baseline against which the amount of looking to the two novel durations and to the novel syllable was assessed to determine whether significant response recovery occurred. To rule out possible fatigue effects, each infant also saw and heard a single segment of a cartoon prior to the test session (pre-test trial) and after it (post-test trial). An initial overall analysis yielded a significant habituation duration x test trial interaction (p < .05) but no age x trials interaction. Subsequent analyses indicated that infants who were habituated to the 800 ms. syllable exhibited significant response recovery to the 1300 and 1800 ms. syllables and a marginally significant recovery to the novel syllable. In contrast, infants who were habituated to the 1800 ms. syllable did not exhibit significant response recovery to the other two syllable durations but did exhibit significant recovery to the novel syllable. Both groups of infants exhibited highly significant response recovery in the post-test trial indicating that they were not fatigued. Taken together, these findings show that infants can perceive the duration of isolated multimodal syllables but that this ability depends on the duration of the initial stimulus to which they are familiarized. In part, the failure to discriminate following habituation to the longer syllable probably reflects the effects of experience in that long isolated syllables are far less common in everyday speech.
poster
Identical
visual targets moving across each other with equal, constant speed can be
perceived either to bounce off or to stream through each other at the
coincidence point. Sound presented at the coincidence enhances the bouncing
percept (Sekuler et al., 1997). We investigated the development of this
auditory-visual illusion in 4-, 6-, and 8-month old infants (N=240 ) using an
infant-controlled habituation/test design. In experiment 1, infants were
habituated to a visual display consisting of targets moving along oblique
trajectories and a sound that was presented when the two
targets overlapped. In the test trials, the sound was shifted in time and
occurred either at the beginning or at the end of the trial. Results indicated
that regardless of age, infants did not differentiate between the habituation
and test stimuli. Experiment 2 was identical to Experiment 1 except that the
targets moved along horizontal trajectories. Whereas the 4-month olds did not
differentiate between habituation and test stimuli, the 6- as well as the
8-month olds exhibited significant discrimination suggesting that they perceived
the bouncing illusion. Experiment 3 was designed to investigate whether the
older infants perceived the bouncing illusion, or whether they used other (e.g.,
temporal) cues to differentiate between the habituation and the test stimuli of
Experiment 2. 4-, 6- and 8-month old infants were habituated with the display
used in Experiment 2, but were tested with a display where the two targets
actually bounced against each other. The infants did not differentiate between
the induced and the actual collision. Another group was habituated with a sound
occuring either at the beginning or at the end of a trial, and
was tested with a sound that was synchronous with the overlap of the two
targets. This group successfully discriminated between the habituation and the
test stimuli. Together, these results reveal that the onset of the bouncing
percept occurs around 6 months of age. It has recently been
suggested that the illusion occurs in adults because the sound draws attention
away from the perception of the motion, thereby increasing the
probability of a bouncing percept (Watanabe & Shimojo, 1999). These findings
suggest that the perception of bouncing observed in the 6- and 8-month olds
results from their ability to attend to the crossmodal stimulus as a whole,
while for the 4-month olds the motion perception task was drawing all available
attentional resources. This latter effect may also account for the negative
results in Experiment 1 since it is known that oblique motion displays are more
demanding for infants compared to horizontal or vertical motion displays. Taken
together, the present study suggests that the bouncing perception requires the
crossmodal attentional system to be sufficiently developed, and that this
development occurs around 6 months of life.
poster
no abstract
poster
Evidence from studies of birds and mammals suggests that multimodal sensory stimulation has greater salience than unimodal sensory stimulation in early development. In particular, research with both animal and human infants has shown that multimodal stimulation can influence attentional selectivity and perceptual learning in the weeks and months following birth. This study examined the effects of reduced amounts of multimodal stimulation during the early postnatal period on the species-typical perceptual responsiveness of bobwhite quail chicks. Group-reared chicks were housed in one of three conditions following hatching, providing subjects ongoing exposure to (a) the bobwhite maternal call (unimodal auditory condition), (b) a bobwhite hen model (unimodal visual condition),or (c) a bobwhite hen paired with the maternal call (multimodal condition).Chicks' preferences for unimodal and multimodal maternal cues were subsequently assessed at 72 hr, 96 hr, 120 hr, or 144 hr following hatching. Results revealed that limitations on normally available multimodal experience following hatching had a significant effect on chicks' early perceptual organization. Regardless of whether subjects received unimodal auditory or unimodal visual experience with maternal cues, chicks showed altered patterns of auditory responsiveness, visual responsiveness, and intersensory (audio-visual) responsiveness when compared to control chicks receiving multimodal stimulation. Most surprising was the finding that chicks reared with ongoing unimodal visual exposure to the bobwhite hen did not appear to benefit from this exposure, failing to prefer this familiar hen over a species-atypical scaled quail hen even after six days of visual experience with the species-typical hen.Only when chicks received multimodal exposure to the hen and call together in the days following hatching did auditory, visual, and intersensory responsiveness to maternal cues develop normally. These results highlight the functional distinction between unimodal and multimodal sensory stimulation in early development and demonstrate the importance of postnatal multimodal experience to the emergence of species-typical perception.
poster
Most multimodal events make both amodal and arbitrary intersensoryrelations available. Prior research from my lab demonstrated adevelopmental lag between the emergence of infants' sensitivity to amodaland arbitrary relations in a given set of multimodal events. For example,by 3-months of age, infants detect the amodal relations (temporalsynchrony and object composition) uniting the sights and sounds of anobject impacting a surface. However, not until 7-months (and not at 3- or5-months) did infants detect the arbitrary relation between thecolor/shape of the object and the pitch of its impact sound, despite thefact that they could discriminate these pitch and color/shape changes by3-months of age (Bahrick, 1992, 1994). The present research explored thebasis for this developmental lag. According to the intersensory redundancy hypothesis recentlyproposed by Bahrick & Lickliter (in press), in early infancy wheninformation is presented redundantly across two sensory modalitiessimultaneously, attention is selectively focused on amodal information andmodality- specific properties are relatively unattended. Thus, accordingto this view, the developmental lag observed between sensitivity to amodalversus arbitrary relations is likely a matter of attentional saliencerather than the result of limitations to the infant's ability to link uparbitrary audio-visual information. If this is true, then enhancing theattentional salience of modality specific properties, should allow infantsto demonstrate the ability to detect modality-specific audio-visualrelations at an earlier age (e.g., 5- months vs 7-months). Thus, in thepresent study, 5-month-old infants were tested in the same procedure asbefore (Bahrick, 1994), however the salience of the modality- specificcontrasts was enhanced by making the visual and acoustic contrasts morediscriminable. Twenty-four 5-month-old infants were habituated in aninfant-control procedure to films of two objects striking a surface in anerratic pattern. One of the two objects produced a high, metalic impactsound (it was struck against a cymbal), and the other produced a low,percussive impact sound (it was struck against a drum). Thus, the soundsdiffered in pitch and timber. The two objects also differed in visualappearance along a number of dimensions including color, shape, and typeof impact motion. Four pairs of events were used and they werecounterbalanced across subjects. Test trials were conducted to determineif infants detected the arbitrary relation between the type of sound andvisual appearance of the object. During the test trials, infants receiveda change in the pairing of object and sound. That is, the object that waspaired with the low drum sound was now paired with the high cymbal sound,and vice versa. Results indicated significant visual recovery ( p <.05 )to the change in modality-specific relations. Thus, enhancing thesalience of the modality-specific properties by making the event pairsmore discriminable led to the earlier appearance of sensitivity toarbitrary modality-specific relations. These results suggest that thedevelopmental lag observed between infants' detection of amodal andarbitrary audio-visual relations is in part a result of attentionalsalience rather than limitations to the infant's ability to form arbitraryrelations between modality-specific properties across the senses.
poster
Studies (Gogate & Bahrick, 1998; under review; Gogate,underreview) have shown that preverbal infants (7- to 8-month-olds) learn thearbitrary relations between two syllables and two distinct objects onlywhen temporal synchrony is provided between the spoken syllables and theobjects' motions. The 7-month-olds learned the relations when thesyllables were non-minimal pairs. Only the 8-month-olds learned when theywere minimal pairs. Further, although preverbal infants require synchronyto highlight syllable-object relations for them, verbal infants might notrequire synchrony to learn these relations. Research by Werker andcolleagues appears to support this claim. In the absence of synchrony,verbal infants (14-month-olds) did not map minimal-pair syllables ([bIh]and [dIh]) onto two moving objects, but did map highly distinctnon-minimal pairs ([nim] and [lIf]) onto a different set of moving objects(Stager and Werker, 1997; Werker, Cohen, et al, 1998). To further explorethis issue, we investigated verbal infants' ability to match minimalversus non-minimal syllable pairs with objects in the absence ofsynchrony. Specifically, if distinctiveness is important, then Werker'sfindings should generalize to other minimal and non-minimal pairs evenwhen the same objects (rather than different objects) are used acrosspairs. Thirty-two infants were habituated in one of two conditions (n 16 in each) using an infant-controlled procedure. Infants received twoalternating displays of a moving object (a crab and a porcupine, or a lambchop and a star) along with a spoken syllable under the non-minimal-pair(/tah/ and /gih/) or the minimal-pair condition (/tah/ and /gah/). Theobjects were moved back and forth in an erratic pattern to simulateshowing them to the infant while the syllables were spoken during thepauses between the motions. Following habituation and two (no change)post-habituation trials infants received a switch test to assess learning.Further, 5-min. later, infants also received a two-choice intermodalpreference test to assess syllable-object matching. Infants received twoblocks of six 7-s trials. On each trial they received one of the syllablesalong with the two moving objects side-by-side as dictated by theirhabituation condition. Infants' visual search for the syllable-matchedobject reflected learning of the arbitrary relations. Trained observersrecorded infants' visual fixations to the displays. Immediately following habituation, infants of both conditionsshowed no evidence of learning (ps > .1). However, the infants who hadreceived the non-minimal pairs, did show learning of syllable-objectrelations on the intermodal preference test 5-min later. A significantproportion of their longest looks across trials were to thesyllable-matched object on the two blocks of trials considered together (M .56; t (15) 2.37; p .032), and on the first block of trials alone (M .63; t (15) 2.87; p .012). In contrast, infants who received theminimal pairs showed no learning of syllable-object relations (ps > .1). The results of this research replicate Werker's findings, andtogether with our prior work show a developmental progression wherepreverbal infants rely on synchrony for matching words and referentswhereas verbal infants do not. However, even verbal infants are slow tomap syllables and objects in the absence of synchrony. Further, bothpreverbal and verbal infants appear to learn syllable-object relationsearlier when the syllables are highly distinct and later when they areless distinct.
poster
The intersensory relation between the face and voice providescritical cues for linguistic and social communication. In recent research(in press), we replicated and extended past findings (Kuhl & Meltzoff,1984) that 4.5-month-olds can detect a match between visible mouthmovements and heard vowels. In a follow-up study, we found that infants ofthe same age cannot detect a match between visible gender and heard speechwhen a male and a female face are articulating the same vowel in synchrony.This finding would lead to the unlikely conclusion that infants of 4.5months do not detect gender information in the face and voice. To try toascertain whether gender information is indeed available to infants, twofurther studies were conducted with infants aged 4.5 months.In the first study (the 'conflict' study), infants (n32) were seated infront of two monitors, each displaying a female or a male face articulatingdifferent vowels in synchrony. The centrally-located sound matched thegender of one face and the vowel articulation of the other face. Ifinfants do not detect gender information, they should look to the vowelmatch significantly more than to the gender match. Infants spentapproximately the same percentage of total looking time fixating the gender(X51.8) and the vowel (X48.2) match. Thus, conflicting genderinformation appeared to disrupt our previous demonstration of infants'ability to match on the basis of vowel. This suggests that, at some level,infants can detect gender information.In the second study, we eliminated gender match altogether and examinedwhether 4.5-month-old infants are still able to detect equivalent vowelinformation in the face and voice without matching gender information.The same procedure and stimuli were used except that each monitor displayedthe same female or the same male face. Thus, the sound matched the vowelarticulation of only one face but was of the opposite gender of both faces.To date, 19 out of 32 infants have been tested. For the infants tested thusfar, 62.5% of the total looking time was spent on the matching face and 12out of 19 infants looked longer at the match; thus, infants show a trendtoward visual preference for the face that matches the heard vowel.Therefore, when phonetic and gender information are in conflict,4.5-month-olds show no preference for the phonetic match; however, whenonly the gender of the face and voice are in conflict and the voice matchesone of the articulating faces, infants show a trend toward visualpreference for the face that matches the heard vowel. Together, these twostudies suggest that 4.5-month-olds do notice gender relevant cues.However, they may be unable to use auditory information to successfullyguide their visual exploration when several sources of information arecompeting for their attention.
poster
Previous research has shown that infants not only use both tactual (e.g., Streri & Pecheux,1986; and Streri & Spelke, 1989) and visual (e.g., Wilcox, in press; and Wilcox & Baillargeon,1998) modalities to extract object properties, but they can also transfer information from onemodality to the other (e.g., Streri, 1987; and Streri, Spelke, & Rameix, 1993). Specifically, theycanvisually recognize objects they previously only felt. For example, Gibson and Walker (1984)gaveinfants one of two cylinders to haptically explore a rigid or a flexible cylinder. Following hapticexploration, the infants were presented with a visual display of the two cylinders. Infants lookedlonger at the novel cylinder than at the one they had previously felt, as if they extracted therigidityof the object haptically and then visually recognized the object that possessed that property. In the previous intermodal studies, infants were only required to recognize an object asfamiliar. This does not imply that a rich, utile representation of the object was formed duringhapticexploration. Therefore, it cannot be assumed, based on previous research, that infants are able toretrieve information obtained tactually to reason about a visual physical event. [It has beenshownthat infants can reason about visual physical events (e.g, Baillargeon, Kotovsky, & Needham,1995)and about visual events involving compressible objects (Aguiar & Baillargeon, 1998; andBaillargeon, 1987).] The present research examined this possibility. 5- and 6-month-old infants were randomly assigned to either an experimental or a controlcondition. All infants were tested using a two-phase procedure. In the first phase, infants in theexperimental condition haptically explored a rigid ball without ever seeing it. The ball was thentaken away. In the final phase, the infants viewed test events on a stage. They were first showntheball sitting on the left edge of a platform and a small tunnel sitting in the center of the platform.Twoscreens were then raised to occlude the ends of the tunnel. The ball traveled across the stage,disappeared behind the left screen and, after a pause, emerged from behind the right screen, as ifit had traveled through the tunnel. It then paused and reversed direction. This occlusion eventrepeated until the end of the trial. Infants in the control condition were tested in an identicalprocedure except that they haptically explored a compressible ball. The compressible, but nottherigid, ball could fit through the tunnel. Infants in the experimental condition looked reliablylongerat the test events than infants in the control condition, as if they had (a) formed a representationofthe rigid or compressible object in the initial phase, (b) assumed that the ball in the final phasewasthe same ball as the one in the initial phase, and (c) successfully judged that the compressible,butnot the rigid, ball could pass through the tunnel. The results of this experiment demonstrate that infants can draw on information encodedhaptically to reason about a visual physical event. These findings are unique in that they bridgetwoareas of infancy research: intermodal perception and physical reasoning. In addition, they shedlighton how representations are formed and how the perceptual and cognitive systems work inconcert.