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When interacting with infants, humans often alter their speech and song in ways thought to support communication. Theories of human child-rearing, informed by data on vocal signalling across species, predict that such alterations should appear globally. Here, we show acoustic differences between infant-directed and adult-directed vocalizations across cultures. We collected 1,615 recordings of infant- and adult-directed speech and song produced by 410 people in 21 urban, rural and small-scale societies. Infant-directedness was reliably classified from acoustic features only, with acoustic profiles of infant-directedness differing across language and music but in consistent fashions. We then studied listener sensitivity to these acoustic features. We played the recordings to 51,065 people from 187 countries, recruited via an English-language website, who guessed whether each vocalization was infant-directed. Their intuitions were more accurate than chance, predictable in part by common sets of acoustic features and robust to the effects of linguistic relatedness between vocalizer and listener. These findings inform hypotheses of the psychological functions and evolution of human communication.

Parents commonly vocalize to infants to mitigate their distress, especially when holding them is not possible. Here we examined the relative efficacy of parents' speech and singing (familiar and unfamiliar songs) in alleviating the distress of 8- and 10-month-old infants (n = 68 per age group). Parent-infant dyads participated in 3 trials of the Still Face procedure, featuring a 2-min Play Phase, a Still Face phase (parents immobile and unresponsive for 1 min or until infants became visibly distressed), and a 2-min Reunion Phase in which caregivers attempted to reverse infant distress by (a) singing a highly familiar song, (b) singing an unfamiliar song, or (c) expressive talking (order counterbalanced across dyads). In the Reunion Phase, talking led to increased negative affect in both age groups, in contrast to singing familiar or unfamiliar songs, which increased infant attention to parent and decreased negative affect. The favorable consequences were greatest for familiar songs, which also generated increased smiling. Skin conductance recorded from a subset of infants (n = 36 younger, 41 older infants) revealed that arousal levels were highest for the talking reunion, lowest for unfamiliar songs, and intermediate for familiar songs. The arousal effects, considered in conjunction with the behavioral effects, confirm that songs are more effective than speech at mitigating infant distress. We suggest, moreover, that familiar songs generate higher infant arousal than unfamiliar songs because they evoke excitement, reflected in modestly elevated arousal as well as pleasure, in contrast to more subdued responses to unfamiliar songs.

Terminal changes in fundamental frequency provide the most salient acoustic cues to declarative questions, but adults sometimes identify such questions from pre-terminal cues. In the present study, adults and 7- to 10-year-old children judged a single speaker's adult- and child-directed utterances as questions or statements in a gating task with word-length increments. Listeners of all ages successfully used pre-terminal cues to identify utterance type, often only the initial word, and they were more accurate for child-directed than adult-directed utterances. There were age-related differences in identification accuracy and number of words required for correct identification. Age differences were already apparent on the initial (first five) utterances, confirming adults' superior explicit knowledge of intonation patterns that signify questions and statements. Adults' performance improved over the course of the test session, reflecting taker-specific learning, but children exhibited no such learning.

Young children are slow to master conventional intonation patterns in their "yes/no" questions, which may stem from imperfect understanding of the links between terminal pitch contours and pragmatic intentions. In Experiment 1, five to ten-year-old children and adults were required to judge utterances as questions or statements on the basis of intonation alone. Children eight years of age or younger performed above chance levels but less accurately than adult listeners. To ascertain whether the verbal content of utterances interfered with young children's attention to the relevant acoustic cues, low-pass filtered versions of the same utterances were presented to children and adults in Experiment 2. Low-pass filtering reduced performance comparably for all age groups, perhaps because such filtering reduced the salience of critical pitch cues. Young children's difficulty in differentiating declarative questions from statements is not attributable to basic perceptual difficulties but rather to absent or unstable intonation categories.

Music cognition is typically studied with instrumental stimuli. Adults remember melodies better, however, when they are presented in a biologically significant timbre (i.e., the human voice) than in various instrumental timbres (Weiss, Trehub, & Schellenberg, 2012). We examined the impact of vocal timbre on children's processing of melodies. In Study 1, 9- to 11-year-olds listened to 16 unfamiliar folk melodies (4 each of voice, piano, banjo, or marimba). They subsequently listened to the same melodies and 16 timbre-matched foils, and judged whether each melody was old or new. Vocal melodies were recognized better than instrumental melodies, which did not differ from one another, and the vocal advantage was consistent across age. In Study 2, 5- to 6-year-olds and 7- to 8-year-olds were tested with a simplified design that included only vocal and piano melodies. Both age groups successfully differentiated old from new melodies, but memory was more accurate for the older group. The older children recognized vocal melodies better than piano melodies, whereas the younger children tended to label vocal melodies as old whether they were old or new. The results provide the first evidence of differential processing of vocal and instrumental melodies in childhood.

We examined effects of age and culture on children's memory for the pitch level of familiar music. Canadian 9- and 10-year-olds distinguished the original pitch level of familiar television theme songs from foils that were pitch-shifted by one semitone, whereas 5- to 8-year-olds failed to do so (Experiment 1). In contrast, Japanese 5- and 6-year-olds distinguished the pitch-shifted foils from the originals, performing significantly better than same-age Canadian children (Experiment 2). Moreover, Japanese 6-year-olds were more accurate than their 5-year-old counterparts. These findings challenge the prevailing view of enhanced pitch memory during early life. We consider factors that may account for Japanese children's superior performance such as their use of a pitch accent language (Japanese) rather than a stress accent language (English) and their experience with musical pitch labels.

Songs convey emotion by means of expressive performance cues (e.g. pitch level, tempo, vocal tone) and lyrics. Although children can interpret both types of cues, it is unclear whether they would focus on performance cues or salient verbal cues when judging the feelings of a singer. To investigate this question, we had 5- to 10-year-old children and adults listen to song fragments that combined emotive performance cues with meaningless syllables or with lyrics that had emotional implications. In both cases, listeners were asked to judge the singer's feelings from the sound of her voice. In the context of meaningless lyrics, children and adults successfully judged the singer's feelings from performance cues. When the lyrics were emotive, adults reliably judged the singer's feelings from performance cues, but children based their judgements on the lyrics. These findings have implications for children's interpretation of vocal emotion in general and sung performances in particular. (Contains 2 notes and 1 figure.)

Toddlers 15 and 18 months of age were exposed to audiovisual recordings of two novel words paired with novel toys. The words were presented in familiar sentence frames or in isolation. Linguistic context had a greater effect on younger than on older infants. Specifically, 15-month-old boys exhibited successful learning only in the context of single words, and 15-month-old girls did so only for words presented in sentences. Older infants acquired the new words from both contexts, and they learned more rapidly than younger infants. Receptive and expressive vocabulary made no independent contribution to performance.

We evaluated 6- and 7-month-olds' preference and memory for expressive recordings of sung lullabies. In Experiment 1, both age groups preferred lower-pitched to higher-pitched renditions of unfamiliar lullabies. In Experiment 2, infants were tested after 2 weeks of daily exposure to a lullaby at one pitch level. Seven-month-olds listened significantly longer to the lullaby at a novel pitch level than at the original pitch level. Six-month-olds showed no preference but their low-pitch preference was eliminated. We conclude that infants' memory for musical performances is enhanced by the ecological validity of the materials. Moreover, infants' pitch preferences are influenced by their previous exposure and by the nature of the music.

The present review summarizes the available evidence on musicality, or music-related abilities, in infants (birth to 3 years). In the early months of life, infants are responsive to the pitch and temporal patterns of music. Their perceptualskills are similar, in many respects, to those of adults, presumably because of the nature of the human auditory system. Adult-infant differences, where evident, are attributable to infants’ unfamiliarity with the musical conventions of their culture. Musical enculturation proceeds more rapidly for temporal than for pitch processing. Musical exposure, especially the singing of caregivers, is prevalent in infancy. Caregivers’ music-making for infants has consequences for their emotional and social regulation and for their subsequent self-regulation abilities. By the end of their first year, most infants have become music-makers as well as music listeners. They move spontaneously to music, and their patterns of “dancing” undergo considerable change in the subsequent months and years. Early dancing is influenced by the familiarity of the music, and later dancing may include aspects of caregivers’ dance movements. Although the onset of singing occurs considerably later than the onset of dance, early singing is remarkably accurate in terms of its pitch range, pitch contours, rhythmic patterning, and fluency, especially when infants sing in their familiar home environment. [ABSTRACT FROM AUTHOR]

We examined pitch-error detection in well-known songs sung with or without meaningful lyrics. In Experiment 1, adults heard the initial phrase of familiar songs sung with lyrics or repeating syllables (la) and judged whether they heard an out-of-tune note. Half of the renditions had a single pitch error (50 or 100 cents); half were in tune. Listeners were poorer at pitch-error detection in songs with lyrics. In Experiment 2, within-note pitch fluctuations in the same performances were eliminated by auto-tuning. Again, pitch-error detection was worse for renditions with lyrics (50 cents), suggesting adverse effects of semantic processing. In Experiment 3, songs were sung with repeating syllables or scat syllables to ascertain the role of phonetic variability. Performance was poorer for scat than for repeating syllables, indicating adverse effects of phonetic variability, but overall performance exceeded Experiment 1. In Experiment 4, listeners evaluated songs in all styles (repeating syllables, scat, lyrics) within the same session. Performance was best with repeating syllables (50 cents) and did not differ between scat or lyric versions. In short, tracking the pitches of highly familiar songs was impaired by the presence of words, an impairment stemming primarily from phonetic variability rather than interference from semantic processing. [ABSTRACT FROM AUTHOR]

Explored in three experiments children's understanding of emotion in speech. Found gradual developmental change from 4-year-olds' focus on content to adult's focus on paralanguage. Children exhibited greater response latencies to utterances with conflicting cues than to those with nonconflicting cues. They accurately labeled affective paralanguage when propositional emotion cues were obscured by foreign language or by low-pass filtering. (Author/KB)

Two experiments examined the effects of a culture-general factor, pattern redundancy, on the discrimination of five-tone melodies that differed in their adherence to Western tonal conventions, among 9-month olds, 5-year olds, and adults. Increasing exposure seemed to attenuate the effects of the pattern redundancy while amplifying the influence of culture-specific factors. (JPB)

The MacArthur Communicative Development Inventory (a parent-report measure of vocabulary and syntax) was administered to 103 children (mean age 103 months) who participated in a study of temporal resolution as infants. Children who had performed above the median on the temporal resolution task demonstrated better later language development than infants performing below the median. (DB)