Poster group
Details of individual items:
poster
Previous data (Baruch & Drake, 1997) have shown that four-month-old infantsare able to discriminate isochronous sequences only on the basis of tempo ina medium range of tempi (300 to 600 ms IOI). This medium range correspondsto the optimal range in adults for which JND are lowest, and had beenconsidered as a cue for the reference period, which is the period ofspontaneous attentional fluctuations. M. Jones postulated in the dynamicattending theory (1989) that the reference period slows with age, inaccordance with other biological cycles. This research had three goals:first to test tempo discrimination over a range of tempi. Second, tointegrate the perception of a pseudo-melodic pattern, with regular trills,to see whether it reinforces stream segregation and thus improvestempo-discrimination. Third, to test whether observed discrimination will besimilar when infants have to detect an acceleration or a deceleration of tempo. We used an habituation/reaction to novelty paradigm. 72 four-month-oldinfants (mean age 4;13 months) learned to look in the direction of a lamp aslong as they wish to hear the auditory sequence. They were habituated to anisochronous sequence (synthetic-piccolo sounds, 50 ms and 70 dB, A5 formonotone sequence, alternative A5B5 for trill sequence). The tempo was 100,600 or 1200 ms IOI. When habituation criteria was reached, a 15%-faster orslower-tempo sequence was presented. A reaction to novelty was assessed byan increment in observation times for the test trials. To controlspontaneous increase of fixation time, the method of partial lag ofBerthental, Haith & Campos (1983) was used: two other habituation trialswere presented to half the infants before the two test trials, and acorrection was applied to the other half. Each infant was successivelysubmitted to two experimental conditions corresponding to the twopseudomelodic possibilities: monotone and trill sequences, in acounterbalanced order over group. The results showed, as described previously, that infants are able todetect a 15%-acceleration of tempo in monotone sequences for the medium-600ms tempo, but also for the 100 ms tempo condition. This could indicate thatthe optimal range of tempi in which such a discrimination is possible iswider than previously considered. More unexpected is the lack ofdiscrimination for the trill sequences, except for a tendency at the easiertempo of 600 ms. The introduction of a pseudomelodic pattern spoils thedetection of tempo change, may be because it focuses attention on frequencyrange. Finally, a reaction to novelty was observed with accelerationconditions, but infants never reacted to a decrement of tempo sequence. Thisresult is relevant to data indicating in adults that deceleration should bemore difficult to detect, as previously shown for intensity decrement ininfants as in adults.
poster
The aim of this research was to investigate whether infants have any understanding of rhyme. The categorical perception of rhyme was investigated in infants between the ages of 7BD and 13 months through the use of the Conditioned Headturn Paradigm. The infants were presented with rhyming CVC non-words, they were trained to turn their head towards a visual reinforcer when a new category of rhyming CVC non-words was presented. For example, the infants would have been trained to turn their head whenever non-words from the -AD category changed to non-words from the -EG category. However, a failure to be trained on such a task may represent an inadequacy to be conditioned, rather than an inability to categorise rhymes, therefore a simple discrimination task was also included. This discrimination task consisted of training the infants to turn their head when one word changed to a new word. The infants tested can be separated into four distinct groups. The first group, 18.5% of the infants, was unable to be conditioned and did not pass the simple discrimination task. The second group, 11.1%, passed the discrimination task but was unable to demonstrate any understanding that the words presented could be categorised according to their component sounds. The third group, 40.7%, was able to categorise the words that they were trained on according to their rhyming sounds, but were unable to generalise this rule to new sets of rhyming words. The final group, 29.7% were not only able to demonstrate an ability to categorise on the basis of rhyme with the words that they were trained on, but were also able to generalise this rule to new sets of rhymes. Infants were tested on two separate occasions and without exception the infants either stayed in the same group, or they progressed to a higher group. Those infants who did not condition at all during the first session did not condition during the second session, and those infants that conditioned with all the sounds, did so on both sessions. The major shift up the groups takes place with infants that had became bored during the first session, since this session lasted for a longer period of time due to the inclusion of the discrimination task. During the first session a lot of infants appeared to be unable to categorise on the basis of rhyme, however most of them demonstrated this ability during the second session. Despite the large variations in age, no correlation was found between the age of an infant and their ability to categorise according to rhyme. Hence we can conclude that even at 7BD months of age some infants are able to group words according to their component sounds, they show some sensitivity to rhyme.
poster
Infants are able to learn detailed information about complex sequencesof linguistic sounds, such as syllables, after very brief listeningexperiences. In particular, infants are able to use the statisticalproperties of linguistic sound sequences to discover structure, such aswords (e.g., Saffran, Aslin, & Newport, 1996). Recent findings suggestthat infants can also detect statistical patterns in non-linguistictone sequences (Saffran, Johnson, Aslin, & Newport, 1999). Evidently,the ability to perform statistical computations over auditory input isnot limited to linguistic materials.The present study was designed to determine which aspects of tonesequences are detected and used by infants during statistical learning.Tone sequences, in which single notes are sounded one after the next,contain two different types of pitch cues: absolute pitches (e.g., C#),and relative pitches, or the distance between two absolute pitches(e.g., ascending perfect fifth). In the prior research by Saffran etal. (1999) using tone sequences, and in actual music, both absolute andrelative pitch cues are available to learners. The current experimentwas designed to tease apart absolute and relative pitch cues in orderto determine whether infants can successfully learn tone sequencesusing only absolute pitch information. Sixteen eight-month-old infants were familiarized with a 3 minute tonestream, which consisted of 45 tokens of each of four 'tone words'(three-tone sequences), concatenated in random order. The tone streamwas continuous, with no pauses between tones and no rhythmic variation.Statistical cues were the only type of information available fordiscovering 'tone word boundaries'. Following exposure, infants weretested using the headturn preferential listening procedure on tone'words' and 'part-words' (three-tone sequences spanning a wordboundary). Crucially, the words and part-words were chosen so that theycontained the same interval sequence (e.g., an ascending perfect fifthfollowed by a descending minor second), but different absolute pitches(e.g., ADC# versus EAG#). Given this design, infants could onlydiscriminate words from part-words if they retained information aboutabsolute pitch from the learning phase; the words and part-words werenot discriminable based on relative pitch cues. Infants successfully discriminated words from part-words, showing asignificant preference for the relatively novel part-words across twocounterbalanced conditions. These results suggest that in the absenceof reliable relative pitch cues, infants can rely on absolute pitchcues during statistical learning. Ongoing experiments are currentlyexamining the reverse situation, in which relative pitch cues, but notabsolute pitch cues, provide useful information for the testdiscrimination following a statistical learning task. The results fromthese studies, along with prior findings in the infant music perceptionliterature, suggest that infants have access to relatively detailedpitch information and can maintain that information over short delays,even in the absence of musically relevant structure. Future researchwill contrast infants with adults on tone sequence learning tasks, inorder to determine the relative strength of different types of pitchcues as a function of musical experience.
poster
There are claims that temporal abilities in general and gap detection in particular undergo an extended period of development. Werner et al. (1992), for example, reported that infants' threshold for the detection of gaps in continuous noise is 40-80 ms. By contrast, Trehub et al. (1995) found that infants' threshold for the detection of gaps in brief 500-Hz signals is approximately 11 ms (compared to 5.2 ms for adults). The use of extended signals may lead to considerably greater adaptation in infants than in adults, which would pose disproportionate problems for infants. There are other consequences of the use of very brief as opposed to extended signals. Thresholds for very brief signals decrease with increasing frequency, whereas thresholds for continuous tones remain relatively unchanged between 400 and 2000 Hz. Thus, we would predict that infants' thresholds for the detection of gaps in brief 2000-Hz signals would be even lower than those obtained with 500-Hz signals.Infants 6.5 months of age were required to discriminate a pair of 2000-Hz, Gaussian-enveloped tone pips from a short 2000-Hz tone of the same duration and total energy. Groups of 16 infants were tested at one of the following gap durations: 12 ms, 6 ms, or 3 ms. Discrimination performance was significantly different across conditions, F(2, 45) 3.61, p < .05, with the highest and lowest levels of performance obtained for the longest and shortest gaps, respectively. Nonetheless, performance was significantly better than chance in each of the three conditions (ps < .005). Despite the very small age range in our sample (6.4 to 7.2 months), the correlation between age and discrimination performance was small but statistically significant, r .27, p < .05 (one-tailed). Thus, contrary to the claims of very poor temporal processing in infancy, our findings point to unusual precocity, at least in the auditory domain.
poster
In previous research, we established that mothers use subtlydifferent styles of singing for their infant or preschooler.Specifically, mothers sing at a higher pitch level for infants andpronounce the song lyrics more clearly for preschoolers. However, tempo,phrase duration, pause duration, vowel length, and intensity level do notseem to differ across these contexts of singing. Perhaps the substantialsimilarity across contexts may have resulted from the requirement ofsinging the same song for both children. Alternatively, whateverdifferences were evident may have resulted from mothers explicit attemptsto generate distinctive performances of the same song. Mothers in the present study were recorded as they sang songs oftheir choice to their infant (M 8;17 months; range 6;11 to 10;8months) and preschooler (M 2;9 years; range 2;1 to 3;10 years). Inmost cases, mothers selected different songs for their two children, butthe songs were drawn from the same repertoire (i.e., childrens songs).Because of mothers' use of different songs across contexts, their startingpitch did not provide a reasonable estimate of pitch level. Thus, thepitch level of each song was estimated as follows: A scale number wasassigned to each note in the song (e.g., C 1, D 2, E 3, F 4, G 5), and that number was multiplied by the total duration of the notewithin the song (i.e., adding the durations of all occurrences of thatnote). Averaging across all cumulative durations of notes yielded themean pitch. Mothers sang at a mean pitch level that was 1.4 semitoneshigher for infants than for preschoolers, t(18) 2.20, p < .05. In fact,the pitch difference between these contexts was more pronounced than ithad been when mothers sang different renditions of the same song (M .81semitones). Mothers use of different songs for infants and preschoolersprecluded comparisons of verbal articulation. As in the earlier study,however, differences in tempo, phrase duration, pause duration, vowellength, and intensity level were not apparent. These results are consistent with earlier findings of distinctperformances of songs for infant and preschool audiences. Moreover, theresults underline the importance of elevated pitch in songs for infants,as in speech for infants.
poster
Mothers have a distinct style of infant-directed (ID) singing just as theyhave a distinct style of ID speech. Moreover, infants prefer ID singing tonon-ID singing and ID speech to adult-directed speech. Although IDversions of speech and singing are presumed to regulate infant arousal,there have been no attempts to measure such changes in arousal.In the present investigation, we attempted to ascertain the consequences of'live' maternal performances of song on infant arousal, as reflected insalivary cortisol levels. Maternal singing is known to soothe distressedinfants, which should translate to reduced salivary cortisol levels. Forinfants who are not distressed, the consequences are more difficult toanticipate. If singing functions to optimize infant arousal, it may lowerarousal in some circumstances (e.g., distress) and raise it in others(e.g., boredom). Mothers (N 31) were video-recorded as they sang to their 6-month-oldinfants for 10 minutes. Infant saliva samples were gathered immediatelybefore the onset of maternal singing (baseline) and 10 minutes after theend of singing (i.e., 20 minutes from singing onset). Singing, in itself,did not generate significant changes from baseline to post-singingmeasures. We also evaluated the possibility that salivary cortisol levelswere linked to the singer's sensitivity to infants' state. Two independentobservers coded the videotapes for instances of infant loss of interest ordistress (the latter being rare) and for mothers' change of song orperforming style (e.g., tempo change, visual gestures) in response to suchinfant behavior. Maternal sensitivity was indexed by the proportion ofloss-of-interest episodes in which mothers altered the auditory or visualcharacter of their performance. This measure of maternal sensitivity wassignificantly associated with increases in salivary cortisol levels, r .50, p < .02. Specifically, infants tended to show increased cortisollevels to sensitive singing performances and decreased cortisol levels toless sensitive singing performances. These findings are consistent withthe view that sensitive singers succeed in engaging infants' attention andoptimizing their arousal. In other words, it's not a question of what youdo (e.g., singing), but how you do it (e.g., adjusting your singing stylein accordance with the infant's needs).
poster
In the several studies on infants' auditory responses to musical pitch,infants' preference for consonance has been reported. The purpose of thisstudy is to investigate the developmental stages of infants' harmonyperception using the headturn preference procedure. Twelve pieces of musical stimuli, of which six pieces were consonantand the rest were dissonant, were prepared. In the consonant versions, themelodies were accompanied with the totally matched harmonies. On the otherhand, in the dissonant versions, the melodies were accompanied with themismatched ones throughout. Each stimulus was digitally generated withpiano timbre and the length was appropriately 24 seconds. Sixty-ninehealthy participants from four to eleven months of age (36 boys and 33girls) were recruited by the direct mail. Nine data were excluded due tofussing. Each infant sat on its caregiver's lap in the testing booth.After four training trials, they were exposed to twelve stimuli fromspeakers and their looking time was measured. As the result of two-tailed t-tests, four- to five-month-olds listenedlonger to the consonant versions (9.41 s and 7.91 s respectively, t(12) 2.29, p < 0.05), and, six- to seven-month-olds preferred the dissonantversions (8.08 s and 9.46 s respectively, t(21) 2.54, p < 0.05). Therewas no preferential difference in eight- to nine-month olds (6.78 s and 6.95s respectively, t(10) 0.17). Interestingly, the preference for theconsonant versions was found again in ten- to eleven-month-olds (7.9 s and6.6 s respectively, t(12) 2.05, p 0.06). From those results, it can besaid that the preference regarding to musical harmony changes according tothe maturity of infants. The reason why the preference changed might relate with thedevelopmental stages of the perception of musical harmony. Especially thepreferential bias towards the dissonant versions in the six-month-olds wouldindicate a transitional stage of the harmony perception in infancy. Thefollowing discussions should be possible: that is, the four- tofive-month-olds listened longer to the consonant versions than the dissonantones simply because of a strong dislike of mismatched harmony. On the otherhand, the ten-month-olds also listened longer to the consonant one not onlybecause of their pleasant sounds but also because of the 'reasonable'progression of harmony. In other words, while infants below five months oldremain to perceive music as physical sounds, infants over ten months olddeal with music according to the nature of musical harmony. The preferencein the six-month-olds could be describe as follows. The six-month-olds, whoare gradually familiar with musical harmony, were referring to their 'files'on musical harmony while listening to the consonant versions and thedissonant ones. Inevitably, they would pay more attention to the unnaturalharmony than to the natural one. Thus, the preferential changes derivedfrom this study suggest that children become aware of the nature of musicalharmony during their babyhood.
poster
Little is known about the development of auditory sensory sensitivity inpreterm fetuses. There is some evidence to suggest that 30-36 weekgestational age (GA) fetuses demonstrate an excitatory response [heart rate(FHR) accelerations (Bernard & Sontag, 1947; Murphy & Smyth, 1962; Trudinger& Boylan, 1980) and body movements (Hepper & Shaidullah, 1994)] when exposedto brief episodes (2-5s) of relatively loud (>90 dB SPL) airborne sounds.This study was performed to examine the effect of longer episodes of soundon fetal behaviour. Twenty-five, 32-37 week GA fetuses of low-risk pregnant women volunteerswere recruited from antenatal clinics at a teaching hospital in southernOntario, Canada, and tested on one occasion. Each fetus received bothexperimental and no-sound conditions with order of presentationcounterbalanced over subjects; each condition included three, 5 min periods(no- sound/music/no-sound or no-sound/no-sound/no-sound). The music stimulusconsisted of a 5 min piano recording of Brahms lullaby (Op 49, No. 4; key Dflat major) generated for the study by a professional musician. It wasplayed on a DAT system, amplified, and delivered at an average soundintensity of 93 dB (A) through a loud speaker located about 10 cm above thematernal abdomen. FHR was recorded continuously using a Dopplercardiotocograph and body movements were ultrasonographically visualized andvideotaped. FHR was available for 21 fetuses (32-34 weeks GA, n7; 35-37weeks GA, n14). Preliminary analysis of the FHR data over 1 min intervalsshowed that, at 32-34 weeks GA, there was a main effect of condition,F(1,6)14.159, p <.01, and a condition by time interaction, F(5,30)3.378, p<.05. FHR decreased below baseline within 2 min of music onset, while itcontinued to fluctuate during no- sound control. At 35-37 weeks GA, therewas a quadratic time effect, F(1,6)5.459, p<.05; for these older fetuses,an initial FHR decrease during the first minute of music was followed by anincrease back to baseline. Following music offset, there was a time bycondition interaction, F(5,120)2.350, p<.05. For the younger group, FHRremained below baseline for the whole 5 min following offset; the oldergroup showed a significant increase in FHR following offset to about 6 bpmabove baseline. Fetal movements (with the exception of breathing) during thecondition which was presented first (experimental music, n10 or no-soundcontrol, n8) were scored for 18 fetuses (32-34 weeks GA, n8; 35-37 weeksGA, n10) using a computer software package that allowed for frame-by-framecoding of ultrasound records; the time spent moving per minute wascalculated for each fetus. During the second period, there was a linear timeby age by condition interaction, F(1,14)4,852, p<.05; the younger fetusesmoved less during the music period compared to the older fetuses and thecontrol condition. In contrast to an excitatory response observed to brief episodes of sound,preterm fetuses responded to 5 minutes of music with a quieting response(heart rate decelerations and decreased activity levels) possibly indicativeof attention. Response maturation was observed with younger fetuses takinglonger to initiate a response and sustaining the response during and aftermusic. Older fetuses showed a more mature response, a short-lived decreasein FHR to music onset similar to that which has been elicited in termfetuses (> 37 weeks GA) with sound intensities <100 dB.
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At term, brief episodes (2-5s) of relatively loud (> 90 dB SPL) airbornesounds have been shown to elicit fetal heart rate (FHR) and body movementresponses, indicating that prenatal experience with sound has the potentialto influence auditory functional development. The complexity of the stimulus(pure tone, white noise, speech) as well as its intensity and frequencyregulate the threshold and magnitude of a response (see reviews by Lecanuet& Schaal, 1996 and Kisilevsky & Low, 1998). Whether behaviours aremodulated by longer episodes of sound exposure has not been examined and isthe purpose of this study. Forty-three term fetuses ( 37 weeks gestational age) from low-riskpregnant women volunteers recruited from a hospital-based, midwifery clinicin Paris were tested on one occasion. Each fetus received both experimentaland no-sound control conditions with order of presentation counterbalancedover subjects; each condition included three, 5 min periods(no-sound/music/no- sound or no-sound/no-sound/no-sound). The music stimulusconsisted of 5 min of a piano recording of Brahms lullaby (Op 49, No. 4; keyD flat major). Two music stimuli which varied in tempo were generated forthe study ('slow', 69 bpm, and 'fast', 118 bpm); each tempo was randomlyassigned to sequential pairs of subjects. The stimuli were played on a JVCdual cassette player and delivered at one of two different average soundintensities (92 dB Leq, n26 or 98 dB Leq, n17) through a loud speakerlocated approximately 15 cm above the maternal abdomen. FHR was monitored bya Doppler cardiotocograph, recorded, and reduced to HR in beats per minutesfor each minute of testing. Fetal body movements were ultrasonographicallyvisualized and videotaped. Preliminary analyses of FHR data over 1 minintervals revealed a significant interaction of sound intensity and tempo,F(1,39)4.37, p<.05. The data were then analyzed separately for each soundintensity and tempo. The effect of music was limited to the slower tempo at92 dB, t(20)2.35, p<.05; FHR increased within 3 min of music onset. Forbody movements, there was an effect only for the slower tempo. During themusic period, there was a condition by time interaction, F(5,45)2.673,p<.05; the slower tempo resulted in less movement variation in the musiccompared to the control condition. In the post music period, there also wasa condition by time interaction, F(5,40)2.353, p.05; movements increasedover time in the music condition, while they stayed the same in the no-musiccondition. Similar to brief episodes, exposure to longer episodes of a complexairborne sound (music) elicited a FHR increase in term fetuses. However, theheart rate response was limited to the lower intensity and tempo. Bodymovements also were modulated only by slower tempo music. There was adecrease in variability observed during music and an increase in activityfollowing music offset. The observed 'quieting' effect on fetal activityduring music is in-keeping with the results of other studies which haveshown a soothing effect of lullabies in newborns, indicating a continuity ofbehaviour in response to music over the pre- and post-natal periods.
poster
Measuring temporal resolution thresholds in infancy is of interested because of the link that has been made between poor temporal resolution and language-learning problems (e.g., Tallal et al., 1993). With infants, however, it is difficult to separate attentional and motivational factors from perceptual abilities using behavioural methods. Combined with the large variability in the age at which children acquire various aspects of language, children are not typically diagnosed with language-learning problems until at least 3 years of age. The mismatch negativity (MMN) component of the ERP is well suited to measure auditory detection because it does not require attention or a behavioural response, and therefore can be measured identically across the lifespan. At the same time, MMN is correlated with behavioural discrimination. In previous research with adults (Desjardins, et al., 1999) we showed that MMN measures of the smallest silent gap that adults can detect (approximately 4 ms) agree well with behavioural measures of gap detection thresholds. In the study reported here we used the identical procedure to measure temporal resolution thresholds in 6-month-old infants. Three gap stimuli was constructed, each consisting of two 2000 Hz Gaussian-enveloped tone pip markers (S.D. 0.5 ms) whose peak amplitudes were separated by 4, 8, or 12 ms. For each, a no-gap stimulus was constructed that matched the gap stimulus in duration, energy, and roughly in spectral content. For each condition (4, 8, or 12 ms gaps), 80% of the 400 trials were no-gap and 20% were gap trials. Trials were separated by 800 ms. Infants watched a screen saver while EEG recordings were made from 19 sites across the scalp using electrocaps and neuroscan amplifiers and software. In each condition for each infant the gap and no-gap trials were averaged separately and then subtracted to create a difference wave. To date, we have found MMN (i.e, a significant negative deflection in the differences waves at frontal sites using a window of 140 to 250 ms after stimulus onset) for gap sizes of 12 and 8, but not 4, ms. A previous behavioural study using the same stimuli (Trehub et al., 1995) concluded that 6-month-olds as a group could detect gaps of 12 but not 8 ms, although they suspected that some of the infants could hear the 8-ms gaps. This indicates that MMN is a very sensitive measure of gap thresholds in infants. We are currently using MMN to examine whether infants can detect silent gaps of 6 ms.
poster
Previous research has demonstrated a developmental change frombirth to 6-months of age in infants' localization of brief sounds. Whereas newborns are unable to determine the source of brief, 14-mssounds when they are repeated very slowly (< 2/sec); 6-month-old infantsreliably locate the source of such sounds when they are repeated asslowly as once per second. However, the accuracy of their soundlocalization improved as repetition rate was increased from once persecond to twice per second. For adults, performance in a soundlateralization task continues to improve for even more rapid repetitionrates reflecting an integration of acoustic cues to sound sourcelocation across repeated stimulus presentations. To determine whetherinfants' performance would improve with repetition rate, the presentresearch evaluated the accuracy of sound localization by 6-month-oldinfants for repetition rates faster than 2/sec. Each of 40 infants sat on a parent's lap facing a horizontal arrayof 21 loudspeakers in a sound-deadened room. On each trial, noisebursts (60 dBA over a 28 dBA background) were presented from the centerloudspeaker for 3 seconds. The sound then shifted to the left or rightside for up to 10 seconds. An observer examined the infant's behavioron a video monitor and judged the side to which the sound shifted. Correct judgements resulted in a 5-second audio-visual presentation froma video monitor on the corresponding side of the stimulus array. Tointroduce infants to the task, 500 ms duration noise bursts (500-1100Hz) were repeated 1/sec, and the sound shifted to a loudspeaker at 45deg off-midline. When infants responded correctly on 4 out of 5consecutive trials, the sound duration was reduced to 14-ms, and blocksof eight trials were presented at progressively closer azimuths (45, 35,25, 15, and 05 deg). Infants heard one of four stimuli formed from thefactorial combination of two frequencies (40-500 Hz and 2000-5000 Hz)and two repetition rates (4/sec and 8/sec). For each infant at each stimulus location (05-45 deg), a percentcorrect measure adjusted for chance responding (P(C)max) wascalculated. Individual psychometric functions were generated, and theazimuth for which P(C)max equaled 69% was taken as an estimate ofthreshold. ANOVA on the individual thresholds revealed no significantdifferences inthreshold as a function of repetition rate, frequency, or theinteraction between rate and frequency (p's < .25). The overall meanthreshold was 32.61 deg. Comparable thresholds for 6-month-olds'localization of the same noise bursts repeated at 1/sec and 2/sec were36o and 27.3o, respectively. The present findings confirm an earlier report that 6-month-oldinfants can reliably locate the source of repeated brief sounds. Combining across these reports, infants' thresholds decreased withrepetition rate from 1/sec to 2/sec and then progressively increasedfor 4/sec and 8/sec repetition rates. The lower threshold for the 4/secrepetition rate compared to the 8/sec repetition rate contrasts withfindings for adults whose thresholds for lateralizing brief soundsdecrease with increasing repetition rate across the rates presentedhere. The present results suggest that although 6-month-olds localizerepeated brief sounds, they may not integrate acoustic informationacross repeated 'looks' at the stimulus in the same manner as do adults.
poster
A variety of techniques have been developed to assess auditorydiscrimination and preferences in infants. However, none of thesetechniques has been able to provide a measure commonly obtained fromadults: labeling or categorization data. In a typical adult study, twostimuli serve as the labels during training, and each participant mustexceed some minimal level of performance on these endpoints before anumber of generalization stimuli are presented during a two-alternativeforced-choice testing phase. The infant technique that comes closest to ameasure of auditory categorization is the multiple-habituation procedurein which several discriminably different stimuli are presented in randomorder, followed by within- and between-category test stimuli. However,this technique relies on infants' biases to categorize stimuli in certainways, rather than on determining the ease with which infants' attentioncan be directed to certain criterial dimensions. We describe a new technique that employs anticipatory eyemovements to provide a two-alternative forced-choice assessment ofauditory categorization. The infant was seated on its mother's lap infront of a large-screen (32 inch) television display. During training, aseries of 36 discrete trials were presented to each infant in which ananimated cartoon animal appeared randomly on either the right or left sideof the display. Between trials, a vertically oscillating smiley-face wasused to orient the infant's gaze to screen-center. Training trials withthe display on the right were paired with a single presentation of onesound ('quack') and training displays on the left were paired with adifferent sound ('eep'). Initially, there was no delay between thepresentation of the visual display and the sound. However, this delay wasincreased by 300 msec after each block of 4 training trials to a maximumof 2400 msec during testing. After training, each infant was tested until he became fussy (mean 11.2 trials). The direction (right or left) of each eye movement duringthe 2400 msec delay between the presentation of the sound and the cartoondisplay was judged by trained coders from the video tape of a close-upview of the infant's face. Data from 6 4-month-old infants revealed thatno eye movement to either stimulus location was made on 30% of the testtrials. However, for the 70% of trials on which infants made one or moreeye movement to either of the two possible locations, the direction of thelatest eye movement was correct 85% of the time (t(5)6.032 p.002).Additionally, none of the infants scored lower than chance (%50). Thisindicates that the infants were learning to expect the visual display(reward) on the side cued by the auditory stimulus. Although we do not yet have generalization data for auditorystimuli other than those used during training, these results suggest thatanticipatory eye movements can be used to obtain two-alternativeforced-choice categorization data from 5-month-old infants. While only'quacks' and 'eeps' served as the stimuli in this experiment, it shouldbe possible to use other training and generalization stimuli to assesslinguistic and musical categories.
poster
Heart rate (HR), EEG and motor responses to the presentation of series of6-10 sound stimuli (2.5-second tones of 1000, 4000, 250 Hz, 70 dB,interstimulus interval 25 s) were studied in 19 sleeping infants aged 9 -22 weeks from birth. In 17 infants HR responses consisting of threedifferent phases were observed: 1) short-latency HR deceleration (duringthe first second after stimuli onset), 2) HR acceleration peaking at the 3- 5th second, and 3) late HR deceleration at the 6 - 9th second ofpoststimulus time. The 1st and the 2nd phases of the response wererelatively constant during the series of tonal stimuli, but the latedeceleration significantly habituated under tone repetition. Differencesin the dynamics of HR-response components as well as a statisticalanalysis of their interactions proposed a relative independence of the 3phases of the HR response. The HR acceleration might be associated withthe motor response elicited by the sound stimulus. The late HRdeceleration occurred not only to the first tone presentations, but alsounder repetition, if the stimulus evoked EEG-reaction (vertex-potentials)to the onset or both to the onset and offset of the sound. In the lastcase, doubling of the first phase and a late deceleration latencylengthening were observed.The above mentioned phases of poststimulus HR changes are respectivelyconsidered as 1) a vagal-cardial reflex associated with an acousticaladaptive reflex, 2) activation of sympathetic efferents dependent onstartle or defensive reaction, and 3) secondary vagal slowing down ofcardial rhythm, which is obviously related to perception of the novelty ofstimulus, and may thus serve as an indirect sign of orienting reaction.
poster
In order to study newborns' reactivity, discrimination and preference ofacoustic stimuli, a behavioural response such motor activity (MA) could beused. MA has been mainly studied to describe the development of motorpatterns since the foetal stage (De Vries et al., 1984). Less frequent arethe studies using MA as an index of newborns' discrimination (Hepper et al.,1993), since much research has used instead non nutritive sucking (NNS).Our research aims to verify whether MA could be an index of reactivity toheartbeat and of discrimination and preference between the mother'sheartbeat, experienced in the last months of gestation, and another woman'sheartbeat. Further, to evaluate whether there is a prenatal learning of boththe global structure and the pure rhythm of the maternal heartbeat, both theactual and a pure rhythmical version of each heartbeat were used. Using NNS,newborns' discrimination and preference of the maternal actual heartbeat hasindeed been found (Giovanelli et al., 1999).Twelve newborns completed the test, during active sleep, in the third day oflife. The stimuli were maternal and non maternal heartbeat, transmitted withan earphone, in a randomised order. Both stimuli were introduced, after asilent baseline (60 s), first as the actual heartbeat (180 s), then as arhythmic tone extracted from the actual heartbeat (180 s). The test lasted14 minutes. In six newborns MA was recorded, while in the other six MA andNNS were recorded. To codify MA, for each period of 60 s the movements (i.e.extension, flexion, rotation, opening, closing, etc.) of head, superiorlimbs, hands, trunk, inferior limbs, feet and face were examined.Six newborns with only MA. An ANOVA with 3 factors (maternal/non maternal;actual/rhythmic; time: 3 periods of 60 s.) was conducted: interactionbetween maternal/non maternal and time was significant for total movements(p.049), for movements of inferior limbs and feet (p.05) and for movementsof superior limbs and hands (p.072). From the baseline to the first 60 s ofthe actual maternal heartbeat, total movements (p.04), inferior limbs andfeet movements (p.05), superior limbs and hands movements (p.007) increasesignificantly (ANOVA 2 factors: maternal/non maternal; base60s-test60s).Six newborns with MA and NNS. From the baseline to the first 60 s of bothmaternal and non maternal actual heartbeat, total movements (p .02),inferior limbs and feet movements (p.03), face movements (p.05) increasesignificantly (ANOVA 2 factors: maternal/non maternal; base60s-test60s).These first results show that MA, when NNS is not recorded, is an index ofneonatal discrimination and preference of the maternal actual heartbeat.Instead, when NNS is simultaneously recorded, MA appears an index ofreactivity.ReferencesDeVries, J. I. P., Visser, G. H. A., Prechtl, H. F. R. (1984). Fetalmotility in the first half of pregnancy. In H. F. R. Prechtl (Eds.),Continuity of neural function from prenatal to postnatal life. London:Spastics International Medical Publications.Giovanelli, G., Callegati, I., Sansavini, A., Tuozzi, G. (1999). Rispostecomportamentali e fisiologiche neonatali di fronte al battito cardiaco dellamadre e di un'estranea. Giornale Italiano di Psicologia, 2, 339-357.Hepper, P. G., Scott, D., Shahidullah, S. (1993). Newborn and fetal responseto maternal voice. Journal of Reproductive and Infant Psychology, 11,147-173.