Vocal imitation between mothers and infants

The aim of the present mixed cross-sectional and longitudinal study was to observe and describe some aspects of vocal imitation in natural mother-infant interaction. Specifically, maternal imitation of infant utterances was observed in relation to the imitative modeling, mirrored equivalence, and social guided learning models of infant speech development. Nine mother-infant dyads were audio-video recorded. Infants were recruited at different ages between 6 and 11 months and followed for 3 months, providing a quasi-longitudinal series of data from 6 through 14 months of age. It was observed that maternal imitation was more frequent than infant imitation even though vocal imitation was a rare maternal response. Importantly, mothers used a range of contingent and noncontingent vocal responses in interaction with their infants. Mothers responded to three-quarters of their infant's vocalizations, including speech-like and less mature vocalization types. The infants’ phonetic repertoire expanded with age. Overall, the findings are most consistent with the social guided learning approach. Infants rarely imitated their mothers, suggests a creative self-motivated learning mechanism that requires further investigation.     

ACOUSTIC ANALYSIS OF ORAL PRODUCTIONS OF INFANTS LATER DIAGNOSED WITH AUTISM AND THEIR MOTHER

Research on early signs of autism in social interactions often focuses on infants’ motor behaviors; few studies have focused on speech characteristics. This study examines infant‐directed speech of mothers of infants later diagnosed with autism (LDA; n = 12) or of typically developing infants (TD; n = 11) as well as infants’ productions (13 LDA, 13 TD). Since LDA infants appear to behave differently in the first months of life, it can affect the functioning of dyadic interactions, especially the first vocal productions, sensitive to expressiveness and emotions sharing. We assumed that in the first 6 months of life, prosodic characteristics (mean duration, mean pitch, and intonative contour types) will be different in dyads with autism. We extracted infants’ and mothers’ vocal productions from family home movies and analyzed the mean duration and pitch as well as the pitch contours in interactive episodes. Results show that mothers of LDA infants use relatively shorter productions as compared to mothers talking to TD infants. LDA infants’ productions are not different in duration or pitch, but they use less complex modulated productions (i.e., those with more than two melodic modulations) than do TD. Further studies should focus on developmental profiles in the first year, analyzing prosody monthly.     

Infants' responses to mothers' imitative behaviors

Several investigators have suggested that young infants' smiles and vocalizations following their mothers' imitative behaviors might reflect infant recognition that the mother's behavior is imitative or at least contingent. This study investigated whether infants smile and vocalize more frequently subsequent to maternal imitative than non-imitative behavior during both spontaneous and imitative face-to-face interactions. Fourteen 3 1/2-month-old infants and their mothers were videotaped in these two face-to-face interaction situations. The infants vocalized more frequently during the imitative situation and infant vocalizations plus simultaneous smiling, and vocalizations occurred more often following maternal imitative than non-imitative behavior. Although these data suggest that infant vocalizations and simultaneous smiles and vocalizations may reflect the infants' recognition of maternal imitative behavior, they do not establish definitively that it is the imitation per se vs. the contingency aspect that is recognized by the infant.     

Reinforcement of vocalizations through contingent vocal imitation

Maternal vocal imitation of infant vocalizations is highly prevalent during face-to-face interactions of infants and their caregivers. Although maternal vocal imitation has been associated with later verbal development, its potentially reinforcing effect on infant vocalizations has not been explored experimentally. This study examined the reinforcing effect of maternal vocal imitation of infant vocalizations using a reversal probe BAB design. Eleven 3- to 8-month-old infants at high risk for developmental delays experienced contingent maternal vocal imitation during reinforcement conditions. Differential reinforcement of other behavior served as the control condition. The behavior of 10 infants showed evidence of a reinforcement effect. Results indicated that vocal imitations can serve to reinforce early infant vocalizations.     

Prelinguistic evolution in early hominins: whence motherese?

In order to formulate hypotheses about the evolutionary underpinnings that preceded the first glimmerings of language, mother-infant gestural and vocal interactions are compared in chimpanzees and humans and used to model those of early hominins. These data, along with paleoanthropological evidence, suggest that prelinguistic vocal substrates for protolanguage that had prosodic features similar to contemporary motherese evolved as the trend for enlarging brains in late australopithecines/early Homo progressively increased the difficulty of parturition, thus causing a selective shift toward females that gave birth to relatively undeveloped neonates. It is hypothesized that hominin mothers adopted new foraging strategies that entailed maternal silencing, reassuring, and controlling of the behaviors of physically removed infants (i.e., that shared human babies' inability to cling to their mothers' bodies). As mothers increasingly used prosodic and gestural markings to encourage juveniles to behave and to follow, the meanings of certain utterances (words) became conventionalized. This hypothesis is based on the premises that hominin mothers that attended vigilantly to infants were strongly selected for, and that such mothers had genetically based potentials for consciously modifying vocalizations and gestures to control infants, both of which receive support from the literature.     

Learning how to learn from social feedback: The origins of early vocal development

Infants’ prelinguistic vocalizations reliably organize vocal turn-taking with social partners, creating opportunities for learning to produce the sound patterns of the ambient language. This social feedback loop supporting early vocal learning is well-documented, but its developmental origins have yet to be addressed. When do infants learn that their non-cry vocalizations influence others? To test developmental changes in infant vocal learning, we assessed the vocalizations of 2- and 5-month-old infants in a still-face interaction with an unfamiliar adult. During the still-face, infants who have learned the social efficacy of vocalizing increase their babbling rate. In addition, to assess the expectations for social responsiveness that infants build from their everyday experience, we recorded caregiver responsiveness to their infants’ vocalizations during unstructured play. During the still-face, only 5-month-old infants showed an increase in vocalizing (a vocal extinction burst) indicating that they had learned to expect adult responses to their vocalizations. Caregiver responsiveness predicted the magnitude of the vocal extinction burst for 5-month-olds. Because 5-month-olds show a vocal extinction burst with unfamiliar adults, they must have generalized the social efficacy of their vocalizations beyond their familiar caregiver. Caregiver responsiveness to infant vocalizations during unstructured play was similar for 2- and 5-month-olds. Infants thus learn the social efficacy of their vocalizations between 2 and 5 months of age. During this time, infants build associations between their own non-cry sounds and the reactions of adults, which allows learning of the instrumental value of vocalizing.     

Synchrony in mother-infant vocal interactions revealed through timed event sequences

This report extends a previous cross-cultural study of synchrony in mother-infant vocal interactions (Bornstein et al., 2015) to immigrant samples. Immigrant dyads from three cultures of origin (Japan, South Korea, South America) living in the same culture of destination (the United States) were compared to nonmigrant dyads in those same cultures of origin and to nonmigrant European American dyads living in the same culture of destination (the United States). This article highlights an underutilized analysis to assess synchrony in mother-infant interaction and extends cross-cultural research on mother-infant vocal interaction. Timing of onsets and offsets of maternal speech to infants and infant nondistress vocalizations were coded separately from 50-min recorded naturalistic observations of mothers and infants. Odds ratios were computed to analyze synchrony in mother-infant vocal interactions. Synchrony was analyzed in three ways -- contingency of timed event sequences, mean differences in contingency by acculturation level and within dyads, and coordination of responsiveness within dyads. Immigrant mothers were contingently responsive to their infants’ vocalizations, but only Korean immigrant infants were contingently responsive to their mothers’ vocalizations. For the Japanese and South American comparisons, immigrant mothers were more contingently responsive than their infants (but not robustly so for South American immigrants). For the Korean comparison, mean differences in contingent responsiveness were found among acculturation groups (culture of origin, immigrant, culture of destination), but not between mothers and infants. Immigrant dyads’ mean levels of responsiveness did not differ. Immigrant mothers’ and infants’ levels of responsiveness were coordinated. Strengths and flexibility of the timed event sequential analytic approach to assessing synchrony in mother-infant interactions are discussed, particularly for culturally diverse samples.     

The social environments of early infancy in Japan and the United States

The social environments of early infancy in Japan and the United States were compared in terms of the context of caregiving and the quality of the month-infant interaction. Mothers of 17 Japanese infants and 17 infants in the United States were interviewed in their homes about the experiences that they provided for their 4-month-old infants, and mother-infant interactions were recorded on videotape. Levels of parents' education were similar in both countries. The context of the infant's development varied substantially with culture. Mothers in the United States provided a greater variety of experiences on the HOME and care of Japanese infants tended to be more exclusively provided by mothers whereas care of infants in the United States was shared by fathers and other caregivers to a greater extent. Examination of behaviour frequencies during mother-infant interaction indicated that mothers in Japan provided their infants with more vocal input and more physical play than mothers in the United States and Japanese mothers were more vocally responsive to their infants' vocalizations.     

Some Personality Characteristics of the Culturally Disadvantaged

The relationship between sensitive maternal behavior and mother-infant vocalization during feedings was examined in an effort to determine this situational meaning of Ainsworth's concept of sensitivity. Ss were 28 white, middle-class mothers and their infants. Excerpts of home feedings videotaped at 6 and 9 months were coded for frequency of contingent vocal interaction and quality of vocal affect. Sensitive mothers were distinguished from insensitive mothers at each age period by differing vocal patterns. At 6 months, infants of sensitive mothers vocalized significantly less than did infants of insensitive mothers. Mothers in both groups responded to their infants' vocalizations equally as often. At 9 months, infants in both groups vocalized the same amount, while sensitive mothers vocalized more often in response to their infants than did insensitive mothers. The only significant difference in vocal affect was found in the greater positive affect among sensitive mothers at 9 months.     

Consistent responses of human mothers to prelinguistic infants: the effect of prelinguistic repertoire size

The salience of infants' vocal and visual cues was examined to evaluate the efficacy of prelinguistic vocalizations to guide adult behavior. A videotape, constructed of brief behavioral episodes from 3 infants with different-sized vocal repertoires, was played to 40 mothers of prelinguistic infants. Playback mothers' responses to the episodes were consistent, demonstrating that preverbal behavior elicits comparable reactions across unfamiliar receivers. The audio and video components of the infants' episodes were then recombined. As the vocal repertoire of the stimulus infants increased, changes in the audio component more often led playback mothers to change responses. Thus, playback mothers used vocalizations as cues as the infants' vocal repertoires became larger.     

Contingency, imitation, and affect sharing: Foundations of infants' social awareness

Predictions about the role of contingency, imitation, and affect sharing in the development of social awareness were tested in infants during natural, imitative, and yoked conditions with their mothers at 5 and 13 weeks of age. Results showed that at both ages, infants of highly attuned mothers gazed, smiled, and vocalized positively more during the natural than during the imitative and yoked conditions, whereas they increased negative vocalizations during the yoked conditions. In contrast, infants of less attuned mothers did not differentiate between the conditions, except at 13 weeks when these infants increased their gazes during the imitative condition. Whereas contingency and imitation draw infant attention to conspecifics, affective communication appears to lay the foundation for infants' social awareness.     

Melodies in caregivers' speech: A species-specific guidance towards language

The author reports on a series of integrated studies on melodic contours in infant-directed (ID) speech. ID melodies in speech are taken as an instructive example of intuitive parenting in order to review current evidence on its forms, functions and determinants. The forms and functions of melodic prototypes are compared in terms of universal properties and individual and/or cultural variability across samples of German, Chinese and American mothers, and German mothers and fathers with their 2- and 3-month-old infants. Microanalyses of interactional contexts show that forms and functions of ID melodies are intimately related to typical dimensions of intuitive caregiving–arousing/soothing, turnyielding/turn-closing, approving/disapproving. The communicative functions of ID melodies as both categorical and graded signals are discussed with respect to the current knowledge on infant responses to ID speech and on early speech perception. According to a comprehensive longitudinal study of ID speech in relation to stages of infant vocalization, ID speech results from fine-tuned adjustments in various prosodic and linguistic features to developmental changes in infants' perceptual and vocal competence. ID melodies evidently have the potential to draw infant attention to caregivers' speech, to regulate arousal and affect in infants, to provide models for imitation, to guide infants in practising communicative subroutines and to mediate linguistic information. Current evidence suggests that the melodies in caregivers' speech provide a species-specific guidance towards language acquisition.     

Patterns of maternal and infant imitation during play

In contrast to recent experimental studies that have sought to establish the infant's ability to imitate, the goal of the current study was to establish the actual performance of imitation by infants and their mothers during episodes of face-to-face play. Three-min play episodes of 20 mothers and their 13- to 16-week-old infants were videotaped. Instances of mouth openings, lip movements, tongue protrusions, smiling, and vocalizations by both partners were coded. Sequential analyses revealed stochastic patterns of imitation by both interactants. Mothers contingently imitated initiations by their infants and were more likely to make like initiations during action in the same category by their infants. Infants did not show onset-to-onset imitation but did show an increased likelihood to initiate actions when their mothers were engaged in a like action. That imitation by the mother is a pervasive characteristic of such interactions is consistent with earlier suggestions of its role in the acquisition of social and emotional skills. The results suggest that infants also display patterns of matching in early social interactions.     

The beginning of conversation: Early patterns of mother-infant vocal responsiveness

Microanalytic techniques were used to characterize the structure of the prespeech communication of 4-month-old infants and their mothers. Two observers continuously recorded the interactive behavior of mothers and their infants during hour-long observations in the homes of 25 families. Loglinear models were used to examine the extent to which the vocal behavior of one person was conditional upon the vocal behavior of the partner. Within the limits of this microanalytic approach, analyses indicated that patterns of mother-infant vocal exchange were structurally similar to patterns of adult conversation. Initial vocal responses were followed by suppression of vocalization, allowing the partner to join the conversation. The comparative effectiveness of vocal behavior as an elicitor of vocalization and as a response to vocalization was shown for mothers and infants relative to the other behaviors observed. Vocalization served as a modulator of visual attentiveness: When the partner was not visually attentive, vocalization elicited visual attention.     

The social functions of babbling: acoustic and contextual characteristics that facilitate maternal responsiveness

What is the social function of babbling? An important function of prelinguistic vocalizing may be to elicit parental behavior in ways that facilitate the infant's own learning about speech and language. Infants use parental feedback to their babbling to learn new vocal forms, but the microstructure of parental responses to babbling has not been studied. To enable precise manipulation of the proximal infant cues that may influence maternal behavior, we used a playback paradigm to assess mothers’ responsiveness to prerecorded audiovisual clips of unfamiliar infants’ noncry prelinguistic vocalizations and actions. Acoustic characteristics and directedness of vocalizations were manipulated to test their efficacy in structuring social interactions. We also compared maternal responsiveness in the playback paradigm and in free play with their own infants. Maternal patterns of reactions to babbling were stable across both tasks. In the playback task, we found specific vocal cues, such as the degree of resonance and the transition timing of consonant‐vowel syllables, predicted contingent maternal responding. Vocalizations directed at objects also facilitated increased responsiveness. The responses mothers exhibited, such as sensitive speech and vocal imitation, are known to facilitate vocal learning and development. Infants, by influencing the behavior of their caregivers with their babbling, create social interactions that facilitate their own communicative development.     

Effects of Labelled Gender on Vocal Communication of Young Women with 4-month-old Infants

Most of the previous studies analyzing the effect of gender label on adults' interactive behaviours with infants concluded that gender stereotypes affect adults' behaviours more than the actual behaviours or characteristics of the infants. These stereotypes and their ensuing behaviours would contribute to the differential socialization experiences of infants according to their gender. The objective of the present study was to investigate further the effect of gender label on adults' vocal communication with infants. Therefore, the prosodic and content features of the language addressed by young women to infants presented as girls and as boys were examined. Sixteen women were observed during two 5-minute sessions of face-to-face interaction with 3-to-4-month-old infants, one introduced as a girl, the other as a boy, in a counterbalanced order. Six girls and four boys served as stimuli. The number of utterances addressed to the infants, their duration and fundamental frequency, as well as the prosodic contour and the content of each vocalization were measured. Results indicated only one significant gender label effect: Women referred more frequently to infant's global motor activity when the infant was presented as a boy. This observation is congruent with other data. However, our results do not demonstrate a consistent pattern of gender label effect when women are talking to unfamiliar infants in such a context.     

Newborns discriminate utterance-level prosodic contours

Prosody is the fundamental organizing principle of spoken language, carrying lexical, morphosyntactic, and pragmatic information. It, therefore, provides highly relevant input for language development. Are infants sensitive to this important aspect of spoken language early on? In this study, we asked whether infants are able to discriminate well-formed utterance-level prosodic contours from ill-formed, backward prosodic contours at birth. This deviant prosodic contour was obtained by time-reversing the original one, and super-imposing it on the otherwise intact segmental information. The resulting backward prosodic contour was thus unfamiliar to the infants and ill-formed in French. We used near-infrared spectroscopy (NIRS) in 1-3-day-old French newborns (n = 25) to measure their brain responses to well-formed contours as standards and their backward prosody counterparts as deviants in the frontal, temporal, and parietal areas bilaterally. A cluster-based permutation test revealed greater responses to the Deviant than to the Standard condition in right temporal areas. These results suggest that newborns are already capable of detecting utterance-level prosodic violations at birth, a key ability for breaking into the native language, and that this ability is supported by brain areas similar to those in adults.

Research Highlights

• At birth, infants have sophisticated speech perception abilities.
• Prosody may be particularly important for early language development.
• We show that newborns are already capable of discriminating utterance-level prosodic contours.
• This discrimination can be localized to the right hemisphere of the neonate brain.

     

Generalized imitation within three response classes in typically developing infants

Effects of modeling and contingent praise on infant imitation of three different responses was analyzed. Generalization to nonreinforced probe models was assessed both within and across response types. Three 12- to 14-month-old infants and their mothers participated in this study. During baseline the mothers provided models only. During treatment mothers modeled and also praised contingent upon infant matching of the training models. During interspersed probe trials the mothers modeled different responses, which, if matched by the infant, produced no praise. The three responses modeled were motor-with-toy, motor-without-toy, and vocal responses. The dependent measure was the percentage of maternal models that were matched by the infant within 6 s. Nonmatching responses of the same response type were also measured. Results showed a systematic increase in the percentages of training and probe models matched by the three infants following the introduction of the model-and-praise treatment condition. Nonmatching responses did not systematically increase. Thus, imitation generalized within response class, but not across response classes.     

Recognizing intentions in infant-directed speech: evidence for universals

In all languages studied to date, distinct prosodic contours characterize different intention categories of infant-directed (ID) speech. This vocal behavior likely exists universally as a species-typical trait, but little research has examined whether listeners can accurately recognize intentions in ID speech using only vocal cues, without access to semantic information. We recorded native-English-speaking mothers producing four intention categories of utterances (prohibition, approval, comfort, and attention) as both ID and adult-directed (AD) speech, and we then presented the utterances to Shuar adults (South American hunter-horticulturalists). Shuar subjects were able to reliably distinguish ID from AD speech and were able to reliably recognize the intention categories in both types of speech, although performance was significantly better with ID speech. This is the first demonstration that adult listeners in an indigenous, nonindustrialized, and nonliterate culture can accurately infer intentions from both ID speech and AD speech in a language they do not speak.     

Expressive timing and interactional synchrony between mothers and infants: cultural similarities, cultural differences, and the immigration experience

The spontaneous vocal interactions of 30 mothers and their 2- to 5-month-old infants from India, France, and the United States were analyzed using an acoustic analysis method. Similarities and differences in vocal interactional patterns were highlighted between the three groups. On the one hand, in the three cultural contexts mother–infant vocal interaction was found to be organized around hierarchical temporal intervals of the same approximate length, had the same balance between regular rhythm and variation (“expressive timing”), and manifested the same coordination between mother and infant vocalization (“interactional synchrony”). On the other hand, the three groups also revealed cultural variability. The Indian mothers had more togetherness with their babies, as indexed by less space between vocal turns and more overlap of mother and baby vocalizations. They also produced a higher ratio of nonverbal to verbal vocalizations. The spontaneous vocal interactions of a group of 30 Indian immigrant dyads were also studied. With respect to culturally variable characteristics, the vocal interaction of immigrant dyads living in the United States showed signs of change in the direction of the host culture. With respect to characteristics shared by all three nonimmigrant groups, the immigrant dyads showed lower levels of expressive timing and interactional synchrony than the nonimmigrant group as a whole.