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Mothers around the world sing to infants, presumably to regulate their mood and arousal. Lullabies and playsongs differ stylistically and have distinctive goals. Mothers sing lullabies to soothe and calm infants and playsongs to engage and excite infants. In this study, mothers repeatedly sang Twinkle, Twinkle, Little Star to their infants ( n = 30 dyads), alternating between soothing and playful renditions. Infant attention and mother-infant arousal (i.e., skin conductivity) were recorded continuously. During soothing renditions, mother and infant arousal decreased below initial levels as the singing progressed. During playful renditions, maternal and infant arousal remained stable. Moreover, infants exhibited greater attention to mother during playful renditions than during soothing renditions. Mothers' playful renditions were faster, higher in pitch, louder, and characterized by greater pulse clarity than their soothing renditions. Mothers also produced more energetic rhythmic movements during their playful renditions. These findings highlight the contrastive nature and consequences of lullabies and playsongs.

Rhythmic movement to music, whether deliberate (e.g., dancing) or inadvertent (e.g., foot-tapping), is ubiquitous. Although parents commonly report that infants move rhythmically to music, especially to familiar music in familiar environments, there has been little systematic study of this behavior. As a preliminary exploration of infants' movement to music in their home environment, we studied V, an infant who began moving rhythmically to music at 6 months of age. Our primary goal was to generate testable hypotheses about movement to music in infancy. Across nine sessions, beginning when V was almost 19 months of age and ending 8 weeks later, she was video-recorded by her mother during the presentation of 60-s excerpts from two familiar and two unfamiliar songs presented at three tempos-the original song tempo as well as faster and slower versions. V exhibited a number of repeated dance movements such as head-bobbing, arm-pumping, torso twists, and bouncing. She danced most to Metallica's Now that We're Dead , a recording that her father played daily in V's presence, often dancing with her while it played. Its high pulse clarity, in conjunction with familiarity, may have increased V's propensity to dance, as reflected in lesser dancing to familiar music with low pulse clarity and to unfamiliar music with high pulse clarity. V moved faster to faster music but only for unfamiliar music, perhaps because arousal drove her movement to familiar music. Her movement to music was positively correlated with smiling, highlighting the pleasurable nature of the experience. Rhythmic movement to music may have enhanced her pleasure, and the joy of listening may have promoted her movement. On the basis of behavior observed in this case study, we propose a scaled-up study to obtain definitive evidence about the effects of song familiarity and specific musical features on infant rhythmic movement, the developmental trajectory of dance skills, and the typical range of variation in such skills.

The present study compared children's and adults' identification and discrimination of declarative questions and statements on the basis of terminal cues alone. Children (8-11 years, n = 41) and adults (n = 21) judged utterances as statements or questions from sentences with natural statement and question endings and with manipulated endings that featured intermediate fundamental frequency (F 0 ) values. The same adults and a different sample of children (n = 22) were also tested on their discrimination of the utterances. Children's judgments shifted more gradually across categories than those of adults, but their category boundaries were comparable. In the discrimination task, adults found cross-boundary comparisons more salient than within-boundary comparisons. Adults' performance on the identification and discrimination tasks is consistent with but not definitive regarding categorical perception of statements and questions. Children, by contrast, discriminated the cross-boundary comparisons no better than other comparisons. The findings indicate age-related sharpening in the perception of statements and questions based on terminal F 0 cues and the gradual emergence of distinct perceptual categories.

The available evidence indicates that the music of a culture reflects the speech rhythm of the prevailing language. The normalized pairwise variability index (nPVI) is a measure of durational contrast between successive events that can be applied to vowels in speech and to notes in music. Music-language parallels may have implications for the acquisition of language and music, but it is unclear whether native-language rhythms are reflected in children's songs. In general, children's songs exhibit greater rhythmic regularity than adults' songs, in line with their caregiving goals and frequent coordination with rhythmic movement. Accordingly, one might expect lower nPVI values (i.e., lower variability) for such songs regardless of culture. In addition to their caregiving goals, children's songs may serve an intuitive didactic function by modeling culturally relevant content and structure for music and language. One might therefore expect pronounced rhythmic parallels between children's songs and language of origin. To evaluate these predictions, we analyzed a corpus of 269 English and French songs from folk and children's music anthologies. As in prior work, nPVI values were significantly higher for English than for French children's songs. For folk songs (i.e., songs not for children), the difference in nPVI for English and French songs was small and in the expected direction but non-significant. We subsequently collected ratings from American and French monolingual and bilingual adults, who rated their familiarity with each song, how much they liked it, and whether or not they thought it was a children's song. Listeners gave higher familiarity and liking ratings to songs from their own culture, and they gave higher familiarity and preference ratings to children's songs than to other songs. Although higher child-directedness ratings were given to children's than to folk songs, French listeners drove this effect, and their ratings were uniquely predicted by nPVI. Together, these findings suggest that language-based rhythmic structures are evident in children's songs, and that listeners expect exaggerated language-based rhythms in children's songs. The implications of these findings for enculturation processes and for the acquisition of music and language are discussed.

Musical behaviours are universal across human populations and, at the same time, highly diverse in their structures, roles and cultural interpretations. Although laboratory studies of isolated listeners and music-makers have yielded important insights into sensorimotor and cognitive skills and their neural underpinnings, they have revealed little about the broader significance of music for individuals, peer groups and communities. This review presents a sampling of musical forms and coordinated musical activity across cultures, with the aim of highlighting key similarities and differences. The focus is on scholarly and everyday ideas about music--what it is and where it originates--as well the antiquity of music and the contribution of musical behaviour to ritual activity, social organization, caregiving and group cohesion. Synchronous arousal, action synchrony and imitative behaviours are among the means by which music facilitates social bonding. The commonalities and differences in musical forms and functions across cultures suggest new directions for ethnomusicology, music cognition and neuroscience, and a pivot away from the predominant scientific focus on instrumental music in the Western European tradition., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

Musicality can be defined as a natural, spontaneously developing trait based on and constrained by biology and cognition. Music, by contrast, can be defined as a social and cultural construct based on that very musicality. One critical challenge is to delineate the constituent elements of musicality. What biological and cognitive mechanisms are essential for perceiving, appreciating and making music? Progress in understanding the evolution of music cognition depends upon adequate characterization of the constituent mechanisms of musicality and the extent to which they are present in non-human species. We argue for the importance of identifying these mechanisms and delineating their functions and developmental course, as well as suggesting effective means of studying them in human and non-human animals. It is virtually impossible to underpin the evolutionary role of musicality as a whole, but a multicomponent perspective on musicality that emphasizes its constituent capacities, development and neural cognitive specificity is an excellent starting point for a research programme aimed at illuminating the origins and evolution of musical behaviour as an autonomous trait., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

The goal of the present study was to ascertain whether children with normal hearing and prelingually deaf children with cochlear implants could use pitch or timing cues alone or in combination to identify familiar songs. Children 4-7 years of age were required to identify the theme songs of familiar TV shows in a simple task with excerpts that preserved (1) the relative pitch and timing cues of the melody but not the original instrumentation, (2) the timing cues only (rhythm, meter, and tempo), and (3) the relative pitch cues only (pitch contour and intervals). Children with normal hearing performed at high levels and comparably across the three conditions. The performance of child implant users was well above chance levels when both pitch and timing cues were available, marginally above chance with timing cues only, and at chance with pitch cues only. This is the first demonstration that children can identify familiar songs from monotonic versions-timing cues but no pitch cues-and from isochronous versions-pitch cues but no timing cues. The study also indicates that, in the context of a very simple task, young implant users readily identify songs from melodic versions that preserve pitch and timing cues.

We explored the possibility of a unique cross-modal signature in maternal speech and singing that enables adults and infants to link unfamiliar speaking or singing voices with subsequently viewed silent videos of the talkers or singers. In Experiment 1, adults listened to 30-s excerpts of speech followed by successively presented 7-s silent video clips, one from the previously heard speaker (different speech content) and the other from a different speaker. They successfully identified the previously heard speaker. In Experiment 2, adults heard comparable excerpts of singing followed by silent video clips from the previously heard singer (different song) and another singer. They failed to identify the previously heard singer. In Experiment 3, the videos of talkers and singers were blurred to obscure mouth movements. Adults successfully identified the talkers and they also identified the singers from videos of different portions of the song previously heard. In Experiment 4, 6- to 8-month-old infants listened to 30-s excerpts of the same maternal speech or singing followed by exposure to the silent videos on alternating trials. They looked longer at the silent videos of previously heard talkers and singers. The findings confirm the individuality of maternal speech and singing performance as well as adults' and infants' ability to discern the unique cross-modal signatures. The cues that enable cross-modal matching of talker and singer identity remain to be determined.

[This corrects the article on p. 492 in vol. 4, PMID: 23966962.].

The current study investigates whether long-term music training and practice are associated with enhancement of general cognitive abilities in late middle-aged to older adults. Professional musicians and non-musicians who were matched on age, education, vocabulary, and general health were compared on a near-transfer task involving auditory processing and on far-transfer tasks that measured spatial span and aspects of cognitive control. Musicians outperformed non-musicians on the near-transfer task, on most but not all of the far-transfer tasks, and on a composite measure of cognitive control. The results suggest that sustained music training or involvement is associated with improved aspects of cognitive functioning in older adults.

THE PRESENT STUDY INTRODUCES A NOVEL TOOL FOR ASSESSING MUSICAL ABILITIES IN CHILDREN: The Montreal Battery of Evaluation of Musical Abilities (MBEMA). The battery, which comprises tests of memory, scale, contour, interval, and rhythm, was administered to 245 children in Montreal and 91 in Beijing (Experiment 1), and an abbreviated version was administered to an additional 85 children in Montreal (in less than 20 min; Experiment 2). All children were 6-8 years of age. Their performance indicated that both versions of the MBEMA are sensitive to individual differences and to musical training. The sensitivity of the tests extends to Mandarin-speaking children despite the fact that they show enhanced performance relative to French-speaking children. Because this Chinese advantage is not limited to musical pitch but extends to rhythm and memory, it is unlikely that it results from early exposure to a tonal language. In both cultures and versions of the tests, amount of musical practice predicts performance. Thus, the MBEMA can serve as an objective, short and up-to-date test of musical abilities in a variety of situations, from the identification of children with musical difficulties to the assessment of the effects of musical training in typically developing children of different cultures.

Infants prefer speech to non-vocal sounds and to non-human vocalizations, and they prefer happy-sounding speech to neutral speech. They also exhibit an interest in singing, but there is little knowledge of their relative interest in speech and singing. The present study explored infants' attention to unfamiliar audio samples of speech and singing. In Experiment 1, infants 4-13 months of age were exposed to happy-sounding infant-directed speech vs. hummed lullabies by the same woman. They listened significantly longer to the speech, which had considerably greater acoustic variability and expressiveness, than to the lullabies. In Experiment 2, infants of comparable age who heard the lyrics of a Turkish children's song spoken vs. sung in a joyful/happy manner did not exhibit differential listening. Infants in Experiment 3 heard the happily sung lyrics of the Turkish children's song vs. a version that was spoken in an adult-directed or affectively neutral manner. They listened significantly longer to the sung version. Overall, happy voice quality rather than vocal mode (speech or singing) was the principal contributor to infant attention, regardless of age.

Cochlear implants have enabled many congenitally or prelingually deaf children to acquire their native language and communicate successfully on the basis of electrical rather than acoustic input. Nevertheless, degraded spectral input provided by the device reduces the ability to perceive emotion in speech. We compared the vocal imitations of 5- to 7-year-old deaf children who were highly successful bilateral implant users with those of a control sample of children who had normal hearing. First, the children imitated several happy and sad sentences produced by a child model. When adults in Experiment 1 rated the similarity of imitated to model utterances, ratings were significantly higher for the hearing children. Both hearing and deaf children produced poorer imitations of happy than sad utterances because of difficulty matching the greater pitch modulation of the happy versions. When adults in Experiment 2 rated electronically filtered versions of the utterances, which obscured the verbal content, ratings of happy and sad utterances were significantly differentiated for deaf as well as hearing children. The ratings of deaf children, however, were significantly less differentiated. Although deaf children's utterances exhibited culturally typical pitch modulation, their pitch modulation was reduced relative to that of hearing children. One practical implication is that therapeutic interventions for deaf children could expand their focus on suprasegmental aspects of speech perception and production, especially intonation patterns.

Japanese 5- to 13-yr-olds who used cochlear implants (CIs) and a comparison group of normally hearing (NH) Japanese children were tested on their perception and production of speech prosody. For the perception task, they were required to judge whether semantically neutral utterances that were normalized for amplitude were spoken in a happy, sad, or angry manner. The performance of NH children was error-free. By contrast, child CI users performed well below ceiling but above chance levels on happy- and sad-sounding utterances but not on angry-sounding utterances. For the production task, children were required to imitate stereotyped Japanese utterances expressing disappointment and surprise as well as culturally typically representations of crow and cat sounds. NH 5- and 6-year-olds produced significantly poorer imitations than older hearing children, but age was unrelated to the imitation quality of child CI users. Overall, child CI user's imitations were significantly poorer than those of NH children, but they did not differ significantly from the imitations of the youngest NH group. Moreover, there was a robust correlation between the performance of child CI users on the perception and production tasks; this implies that difficulties with prosodic perception underlie their difficulties with prosodic imitation., (© 2012 Acoustical Society of America)

Temporal information provided by cochlear implants enables successful speech perception in quiet, but limited spectral information precludes comparable success in voice perception. Talker identification and speech decoding by young hearing children (5-7 yr), older hearing children (10-12 yr), and hearing adults were examined by means of vocoder simulations of cochlear implant processing. In Experiment 1, listeners heard vocoder simulations of sentences from a man, woman, and girl and were required to identify the talker from a closed set. Younger children identified talkers more poorly than older listeners, but all age groups showed similar benefit from increased spectral information. In Experiment 2, children and adults provided verbatim repetition of vocoded sentences from the same talkers. The youngest children had more difficulty than older listeners, but all age groups showed comparable benefit from increasing spectral resolution. At comparable levels of spectral degradation, performance on the open-set task of speech decoding was considerably more accurate than on the closed-set task of talker identification. Hearing children's ability to identify talkers and decode speech from spectrally degraded material sheds light on the difficulty of these domains for child implant users., (© 2012 Acoustical Society of America.)

Musically untrained participants in five age groups (5-, 6-, 8-, and 11-year-olds, and adults) heard sequences of three 1 s piano tones in which the first and third tones were identical (A5, or 880 Hz) but the middle tone was displaced upward or downward in pitch. Their task was to identify whether the middle tone was higher or lower than the other two tones. In experiment 1, 5-year-olds successfully identified upward and downward shifts of 4, 2, 1, 0.5, and 0.3 semitones. In experiment 2, older children (6-, 8-, and 11-year-olds) and adults successfully identified the same shifts as well as a smaller shift (0.1 semitone). For all age groups, performance accuracy decreased as the size of the shift decreased. Performance improved from 5 to 8 years of age, reaching adult levels at 8 years.

Domain-general tuning processes may guide the acquisition of perceptual knowledge in infancy. Here, we demonstrate that 12-month-old infants show an adult-like, culture-specific pattern of responding to musical rhythms, in contrast to the culture-general responding that is evident at 6 months of age. Nevertheless, brief exposure to foreign music enables 12-month-olds, but not adults, to perceive rhythmic distinctions in foreign musical contexts. These findings may indicate a sensitive period early in life for acquiring rhythm in particular or socially and biologically important structures more generally.

Intrinsic perceptual biases for simple duration ratios are thought to constrain the organization of rhythmic patterns in music. We tested that hypothesis by exposing listeners to folk melodies differing in metrical structure (simple or complex duration ratios), then testing them on alterations that preserved or violated the original metrical structure. Simple meters predominate in North American music, but complex meters are common in many other musical cultures. In Experiment 1, North American adults rated structure-violating alterations as less similar to the original version than structure-preserving alterations for simple-meter patterns but not for complex-meter patterns. In Experiment 2, adults of Bulgarian or Macedonian origin provided differential ratings to structure-violating and structure-preserving alterations in complex- as well as simple-meter contexts. In Experiment 3, 6-month-old infants responded differentially to structure-violating and structure-preserving alterations in both metrical contexts. These findings imply that the metrical biases of North American adults reflect enculturation processes rather than processing predispositions for simple meters.

Congenitally deaf Japanese children with cochlear implants were tested on their recognition of theme songs from television programs that they watched regularly. The children, who were 4-9 years of age, attempted to identify each song from a closed set of alternatives. Their song identification ability was examined in the context of the original commercial recordings (vocal plus instrumental), the original versions without the words (i.e., karaoke versions), and flute versions of the melody. The children succeeded in identifying the music only from the original versions, and their performance was related to their music listening habits. Children gave favorable appraisals of the music even when they were unable to recognize it. Further research is needed to find means of enhancing cochlear implants users' perception and appreciation of music.

When utterances contain conflicting emotion cues, 6-year-olds judge emotion from content, even when instructed to judge emotion from paralanguage (Morton & Trehub, 2001). Two experiments examined the nature of this bias. In Experiment 1, priming paralanguage reversed 6-year-olds' normal bias to content. In Experiment 2, 6-year-olds were instructed to listen to paralanguage under various conditions. Children were more likely to follow instructions delivered with feedback than instructions delivered alone. Children who described conflicts between content and paralanguage were more likely to follow instructions than children who did not describe these conflicts. Results suggest that 6-year-olds can judge emotion from paralanguage in the presence of competing content but often remain focused on content because of the way they represent the instructions.

Here we show that good pitch memory is widespread among adults with no musical training. We tested unselected college students on their memory for the pitch level of instrumental soundtracks from familiar television programs. Participants heard 5-s excerpts either at the original pitch level or shifted upward or downward by 1 or 2 semitones. They successfully identified the original pitch levels. Other participants who heard comparable excerpts from unfamiliar recordings could not do so. These findings reveal that ordinary listeners retain fine-grained information about pitch level over extended periods. Adults' reportedly poor memory for pitch is likely to be a by-product of their inability to name isolated pitches.

Children 5 and 9 years of age and adults were required to identify the final words of low- and high-context sentences in background noise. Age-related differences in the audibility of speech signals were minimized by selecting signal-to-noise ratios (SNRs) that yielded 78% correct performance for low-context sentences. As expected, children required more favorable SNRs than adults to achieve comparable levels of performance. A more difficult listening condition was generated by adding 2 dB of noise. In general, 5-year-olds performed more poorly than did 9-year-olds and adults. Listeners of all ages, however, showed comparable gains from context in both levels of noise, indicating that noise does not impede children's use of contextual cues.

We examined the relative stability of pitch, tempo, and rhythm in maternal speech and singing to prelinguistic infants. Mothers were recorded speaking and singing to their infants on two occasions separated by 1 week or more. The pitch level and tempo of identical utterances were highly variable across the 1-week period, but these features were virtually unchanged in song repetitions. Rhythmic patterning was largely maintained in speech, as in song. Mothers' accurate reproduction of their sung performances can be considered a form of absolute pitch and absolute tempo.

Children's understanding of emotion in speech was explored in three experiments. In Experiment 1, 4- to 10-year-old children and adults (N = 165) judged the happiness or sadness of the speaker from cues conveyed by propositional content and affective paralanguage. When the cues conflicted (i.e., a happy situation was described with sad paralanguage), children relied primarily on content, in contrast to adults, who relied on paralanguage. There were gradual developmental changes from 4-year-olds' almost exclusive focus on content to adults' exclusive focus on paralanguage. Children of all ages exhibited greater response latencies to utterances with conflicting cues than to those with nonconflicting cues, indicating that they processed both sources of emotional information. Children accurately labeled the affective paralanguage when the propositional cues to emotion were obscured by a foreign language (Experiment 2, N = 20) or by low-pass filtering (Experiment 3, N = 60). The findings are consistent with children's limited understanding of the communicative functions of affective paralanguage.

Children 5, 9, and 11 years of age and young adults attempted to identify the final word of sentences recorded by a female speaker. The sentences were presented in two levels of multitalker babble, and participants responded by selecting one of four pictures. In a low-noise condition, the signal-to-noise ratio (SNR) was adjusted for each age group to yield 85% correct performance. In a high-noise condition, the SNR was set 7 dB lower than the low-noise condition. Although children required more favorable SNRs than adults to achieve comparable performance in low noise, an equivalent decrease in SNR had comparable consequences for all age groups. Thus age-related differences on this task can be attributed primarily to sensory factors.

Listeners who were 6.5 months, 12 months, 5 years, and 21 years of age were required to discriminate a pair of 500-Hz, Gaussian-enveloped tone pips from a short 500-Hz tone of the same duration and total energy. Groups of 6.5-month-old infants were tested on a single gap duration: 8, 12, 16, 20, 28, or 40 ms. Groups of 12-month-olds were also tested on a single gap duration: 8, 12, 16, or 20 ms. The 5-year-old children and adults were tested on gap durations of 8, 12, and 16 ms. The mean performance of 6.5-month-olds significantly exceeded chance levels on all gap durations except 8 ms, and that of 12-month-olds was above chance levels on all gap durations. For 5-year-old children and adults, mean performance also exceeded chance levels for all gap durations tested. Adults performed significantly better than 5-year-old children on gap durations of 12 and 16 ms. Gap-detection thresholds, defined by a performance criterion of d' = 0.5, were estimated at 11, 5.6, and 5.2 ms for infants, children, and adults, respectively. It is likely that smaller adult-infant differences in the present study compared to those reported in previous research stem from our use of Gaussian-enveloped tone pips and the consequent minimization of adaptation effects.

Infants 8-11 months of age were exposed to repetitions of a 6-tone sequence or melody, then tested for their discrimination of transpositions of that sequence as well as other melodic transformations previously used by Massaro, Kallman, and Kelly with adults. In experiment 1, infants showed evidence of discriminating all transformations from the original melody. In Experiment 2, the task was made more difficult, and infants failed to discriminate transpositions of the original melody as well as transformations that preserved the melodic contour and approximate frequency range of the original melody. By contrast, infants showed evidence of discriminating transformations that violated the contour of the original melody or that included changes in the octaves from which component tones were drawn. This global processing strategy parallels that used by adults with atonal or unfamiliar tonal melodies.

The present study investigated the effect of the relation between conditions at encoding and retrieval on infants' performance on a paired-comparison recognition test. 64 9-month-old infants were given 40 sec to visually or visually and haptically explore a 3-dimensional object. Subsequently, during a 10-sec recognition trial infants were presented with the familiar object and a novel object and their response to each was monitored. Half of the infants from each familiarization condition were permitted to inspect the test-trial stimuli visually, while the other half inspected the stimuli visually and haptically. Thus, in the present study the infant's mode of exploration was either the same during encoding and retrieval or different. Infants demonstrated recognition of the familiar object (via novelty preference) only when mode of exploration was constant across the encoding and retrieval trials. The relation between the conditions at encoding and retrieval is thus an important determinant of the infants' performance on a paired-comparison recognition test.

Infants' processing of temporal parameters of auditory patterns was investigated by assessing the ability of 5-month-old infants to discriminate between multitone patterns with identical component tones but contrasting temporal arrangements of these tones. Following habituation of the cardiac response to a 6-tone stimulus with 2,4 grouping infants were presented with the same tonal sequence with 4,2 grouping. Significant dishabituation was evident, indicating discrimination of different temporal groupings of auditory stimuli.

Masked thresholds for octave-band noises with center frequencies of 0.4, 1, 2, 4, and 10 kHz and for a 1/3-octave-band noise centered at 10 kHz were obtained from listeners 6.5 months to 20.5 years of age at two levels of a broadband masker (0 and 10 dB/cycle). Thresholds declined exponentially as a function of age for all stimuli tested. The rate and extent of this decline, but not its asymptote, were independent of the frequency or bandwidth employed. The time course for this change parallels that found for electrophysiological maturation of more central auditory processes.

Thresholds for octave-band noises with center frequencies of 0.4, 1, 2, 4, and 10 kHz, and 1/3-octave-band noises with center frequencies of 10 and 20 kHz, were obtained from children 3-5 years of age and from a comparison group of adults. Thresholds for all frequencies decreased between 3 and 5 years of age. Thresholds decreased further between 5 years of age and adulthood, except for the 20-kHz stimulus, for which children had lower thresholds than adults. These results are discussed in terms of possible age-related changes in the mechanical properties of the ear and in the efficiency of neural coding.

Infants 9-11 months of age were tested for their discrimination of changes in the melodic contour (direction of successive pitch changes) of brief melodies in the context of discernible variations in key (different absolute frequencies, same intervals) or interval size (different absolute frequencies and frequency ratios, same contour). Infants detected contour changes in both variable contexts, suggesting that they categorize sequences of sounds on the basis of global, relational properties such as melodic contour. Implications of such processing strategies for infants' perception of running speech are considered.

In an attempt to explore the relation between the amount of variability in a stimulus and rate of habituation to that stimulus, 4 groups of infants 4 1/2--5 1/2 months of age were presented with repeated speech stimuli which were synthesized exemplars of [baba], natural exemplars of [baba] or [kaba], or novel syllables of each trial. Infants' cardiac responses to the auditory stimuli were recorded, and the number of trials to a proportional criterion of habituation of the heart-rate decelerative response was determined. Infants were found to habituate most rapidly to the synthesized [baba] stimulus which remained constant across trials and least rapidly to the speech syllables which changed from trial to trial.

Auditory thresholds were determined for infants and adults to half-octave bands of noise centered at 10,000 and 19,000 hertz. Adults were significantly more sensitive than infants at 10,000 hertz, but at 19,000 hertz, adults and infants had comparable thresholds.

Deaf children 6-10 years of age, from oral or bimodal educational programs, were tested in 2 tasks. In the first, they were required to describe a designated picture from a set of 4 pictures so that their mother could identify the intended referent from the 4 alternatives. In the second, they studied a single picture and were subsequently required to identify it from a set of 4 related pictures. Despite greater hearing loss, bimodally educated children provided more differentiated messages than did orally educated children. Bimodally educated children also provided better reformulations of messages that were initially inadequate. Although mothers of orally educated children received inferior messages, they were as successful at selecting the correct referent as were mothers of bimodally educated children. Both groups of deaf children performed at near perfect levels on the picture recognition task, suggesting that performance differences were attributable to differential message formulation skill as opposed to differential visual processing of the referential array.

Localization responses to a broadband noise signal presented against a broadband noise masker were obtained from 12-month-old infants and adults. Two loudspeakers, one to the left and one to the right of the listener, continuously presented identical broadband maskers. On a trial, a broadband signal was added to one of the loudspeakers. Subjects were required to identify the loudspeaker producing the signal. Noise signals were either coherent (from the same noise generator) or incoherent (from an independent noise generator). Both infants and adults found it easier to locate the incoherent signals even when the two types of signals were adjusted to produce equal increments in power. Since monaural performance, after this adjustment, should be equivalent for the two cases, superior performance for incoherent signals implies that binaural processing is involved. The same result was observed in control experiments in which coherent and incoherent signals were presented over earphones to adults. These results suggest that the mechanisms responsible for binaural unmasking are operative by 12 months of age.