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.     

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.     

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.     

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.     

Patterning of infant vocal behavior

Three-month-old infants received two consecutive 5-minute periods of adult social stimulation. In both periods the adult talked, smiled, and touched the infant and in a natural manner tried to elicit vocalizations from the infant. In the first period the adult became unresponsive for 5 sec contingent upon each infant vocalization (time-out, negative reinforcement). In the second period the infant received the same number of time-out periods at the same intervals but independently of vocal responding (yoked, noncontingent control). Negative reinforcement did not suppress infant vocal rate, but the contingent withdrawal of social stimulation did cause the infant to pause more frequently between vocal responses. These pauses generally occurred immediately after the contingently, as compared with the noncontingently, delivered time-out period. The infant appears to recognize the difference between contingent and noncontingent stimulation and pauses after the occurrence of the former. Adult social reinforcement changes the pattern and not the rate of infant vocal responding.     

Effects of delayed reinforcement on infant vocalization rate.

Three previous studies have failed to demonstrate conditioning in infants using a 3-s delay of reinforcement. The effects of a delayed reinforcement schedule on vocalization rates therefore were explored in a single-subject repeated-reversal experimental design for 3 4- to 6-month-old normally developing infants. Each infant received delayed social reinforcement from his or her parent for vocalizing. The comparison condition was a schedule of differential reinforcement of behavior other than vocalizations to control for elicitation by social stimulation. An operant level of infant vocalizations was the initial condition, after which the differential reinforcement schedule was implemented in an across-subjects multiple baseline design. Infants' vocalization rates increased above levels measured during differential reinforcement following onset of the delayed reinforcement condition. Also, vocalization rates decreased during differential reinforcement compared to operant levels. The successful use of delayed reinforcement schedules with infants in this study, as opposed to others, is discussed in terms of procedural differences among them.     

Evaluation of infant vocal conditioning.

The use of the operant conditioning paradigm, as it has been applied to infant social, vocal behavior, reflects a failure to take into account the social nature of human infants over and above the rigid theoretical rationale of the paradigm. It is argued that: (1) the baseline procedure used in operant conditioning studies is methodologically and conceptually invalid; (2) the reinforcing stimulus used in social conditioning studies elicits the very response that it is assigned to reinforce; and (3) the effect of the response-reinforcer relationship is not the reinforcement (strengthening) of vocal response rate.     

Imitation and repetition of prosodic contour in vocal interaction at 3 months

This study investigates vocal imitation of prosodic contour in ongoing spontaneous interaction with 10- to 13-week-old infants. Audio recordings from naturalistic interactions between 20 mothers and infants were analyzed using a vocalization coding system that extracted the pitch and duration of individual vocalizations. Using these data, the authors categorized a sample of 1,359 vocalizations on the basis of 7 predetermined contours. Pairs of identical successive vocalizations were considered to be imitations if they involved both partners or repetitions if they were produced by the same partner. Results show that not only do mothers and infants imitate and repeat prosodic contour types in the course of vocal interaction but they do so selectively. Indeed, different contours are imitated and repeated by each partner. These findings suggest that imitation and repetition of prosodic contours have specific functions for communication and vocal development in the 3rd month of life.     

The timing of verbal/vocal communications between mothers and their infants: a longitudinal cross-cultural comparison

Early dialogues between parent and child constitute an important factor for the acquisition of culture and hence verbal interaction is considered to be a universal parenting system. Parenting strategies and socialization practices are strongly influenced by the cultural conception of the self, prototypically defined as the model of independence and interdependence. Our study focuses on the temporal organization of spontaneous verbal/vocal behavior of 20 German middle-class and 28 Cameroonian Nso mother–infant dyads. The infants and their mothers were observed weekly in a 5 min free-play interaction scene from 0 to 3 months of age. We hypothesized to find different amounts of vocalization time, synchronous vocalizations, and contingent maternal responses in the verbal/vocal patterns of the two samples. The findings indicate cross-cultural differences in the temporal structure of verbal/vocal interactions already during the first three months of life, reflecting underlying differences in the culture-specific modes of verbal interaction.     

Does texting interrupt imitation learning in 19-month-old infants?

Observed disruptions to parent-child interactions during parental media use, such as texting, have been termed technoference. For example, when a language learning interaction was disrupted by a phone call, toddlers were less likely to acquire the word. Other studies demonstrated that parents often exhibit a still face while silently reading information on their cell phones. In the present study, the effect of a text interruption on infant imitation learning was examined. Parents demonstrated three target actions to their infants and then infants were given the opportunity to repeat those interactions. The actions were demonstrated four times. Text interruptions occurred before or between demonstrations. Performance of these groups was compared to a baseline control group where the infant did not see a demonstration of the target actions and a no-interruption group where the parents demonstrated the target actions four times without interruption. Parents were randomly assigned to three conditions, interruption-first condition, one-interruption condition, or three-interruptions condition. Infant behavior was measured during the interruptions. Across text interruption groups parents exhibited high levels of still face during the interruptions (77 %). However, infants in all 3 interruption groups performed significantly above the baseline control indicating learning despite the interruptions. Higher reported maternal reliance on the smartphone was related to poorer imitation performance overall. In contrast, when parents reported that they found it easier to multi-task infant imitation rates were higher. These findings indicate that infants can learn under conditions of brief technoference and that individual differences in family media ecology are associated with learning.     

Maternal and infant affect at 4 months predicts performance and verbal IQ at 4 and 7 years in a diverse population

Using existing longitudinal data from 570 infants in the Maternal Lifestyle Study, we explored the predictive value of maternal and infant affect and maternal vocalizations during 2 minutes of face‐to‐face interactions at 4 months on IQ scores at 4.5 and 7 years. After controlling for demographic factors, maternal depression, and prenatal drug exposure, maternal positive affect and maternal positive vocalizations emerged as predictors of both verbal and performance IQ at 4.5 and 7 years. Although infant positive affect during the interaction with the mother was not predictive of these outcome measures, infant positive affect towards an examiner predicted verbal but not performance IQ at 4.5 years. These results suggest that maternal positive affect may index emotional engagement in interaction that facilitates both verbal and nonverbal cognitive development, while infant social positive affect is specifically related to the acquisition of verbal reasoning abilities. These findings are significant because they are based on a discrete snapshot of observable behavior in infancy (just 2 minutes of interaction), because they extend the range of maternal behaviors and characteristics known to support positive developmental outcomes, and because they are derived from high‐risk infants where prevention efforts may be beneficial. Potential mechanisms for these associations are discussed, as are the clinical implications for identifying dyads most in need of targeted interventions.     

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.     

Influence of a televised model's vocalization pattern on infants

To assess the influence of a televised model's vocalizations on the vocal patterns of infant viewers, 32 infants at 6 months of age were presented either a televised adult model repeating a novel phoneme pattern (/ba/ba/ba/ba) or a control televised presentation of adult conversation selected from typical daytime programming. Sequential analyses of infant vocalizations revealed that infants exposed to the televised model altered their vocalization pattern, as indicated by a significant increase over base line levels in their production of a patterned series of discrete vocalizations. Infants exposed to the televised conversation showned no increase in this pattern of vocalization, and none of the infants in the study produced the novel phoneme (/ba/). The results indicate that televised presentation of discrete, repeated vocalizations can have an influence on the vocalization pattern of infants. The potential role of television in infant development is discussed.     

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.     

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.     

Social processes in communication and cognition in callitrichid monkeys: a review

Studies of vocal development in nonhuman primates have found little evidence for plasticity in vocal production, somewhat more for usage of calls, with the greatest plasticity arising in response to calls of others. Generally, similar results were obtained with callitrichid monkeys, the marmosets and tamarins, but with several interesting exceptions. Infant pygmy marmosets show babbling behavior with improvement in adult call structure related to the amount and diversity of babbling. Adult marmosets alter call structure in response to changes in social partners, and wild marmosets have vocal dialects and modify call structure according to how far they are from other group members, suggesting the potential to modify call structure in different social and environmental contexts, though direct learning of novel vocalizations has not been observed. Infant cotton-top tamarins do not produce adult-like calls in appropriate contexts, at least in the first few months of life, but through food sharing from adults infants learn about appropriate foods and the appropriate contexts for food vocalizations. Tamarins modify call structure and usage with changes in social status. Tamarins, unlike other monkeys tested, can learn to avoid noxious foods through observation of other group members, and can learn about novel food locations. Recent studies provide evidence of contextual imitation in marmosets. The plasticity in vocal communication and evidence of social learning in marmosets and tamarins relative to other monkeys may be related to the cooperative breeding system of marmosets and tamarins. With a high degree of behavioral coordination among group members, there is a priority on monitoring signals and behavior of others and adjusting one's own signals and behavior. This creates the context for vocal plasticity and social learning. Accepted after revision: 23 May 2001 Electronic Publication     

The effect of mother–infant skin-to-skin contact on infants’ response to the Still Face Task from newborn to three months of age

The effect of mother–infant skin-to-skin contact on infants’ developing social expectations for maternal behavior was investigated longitudinally over infants’ first 3 months. Infants with and without skin-to-skin contact engaged with their mothers in the Still Face Task at ages 1 week, 1 month, 2 months, and 3 months. Infants with skin-to-skin contact began responding to changes in their mothers’ behavior with their affect at 1 month; infants without skin-to-skin contact did so at 2 months. At 3 months, infants with skin-to-skin contact increased their non-distress vocalizations during the still face phase, suggesting social bidding to their mothers. Skin-to-skin contact accelerated infants’ social expectations for their mothers’ behavior and enhanced infants’ awareness of themselves as active agents in social interactions.     

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.     

Maternal soothing and infant stress responses: soothing, crying and adrenocortical activity during inoculation

The relation between maternal soothing and infant stress response during inoculation was examined in a sample of 37 mothers and their 3-month-old infants. The mothers' soothing and the infants' cry vocalizations and the mothers' and the infants' salivary cortisol level pre- and post-injection were analysed. There was a positive relation between infants' cry vocalization post-injection and maternal soothing pre- and post-injection. The sample was divided in two sub-groups depending on whether the mothers evidenced most soothing of the infants in the period before (Preparatory group; n=20) or after (Contingent group; n=17) the syringe injection. In the Preparatory group, the duration of infant cry vocalizations was related to amount of maternal soothing before and after the injection, while cry vocalizations in the Contingent group was related to amount of maternal soothing after the injection. The Contingent infants responded to the injection with a significant increase in cortisol, while there was no increase in the Preparatory infants. The Preparatory infants evidenced significantly longer duration of looking at the target stimuli in a visual marking task, suggesting greater difficulties in disengaging attention. These findings indicate that 3-month-olds' stress responses and their mothers' situational behaviour are mutually regulated.     

Differential reinforcement of other-than-vocalization as a control procedure in the conditioning of infant vocalization rate

The purpose of the present study is to demonstrate reinforcement control over infant vocalization rates using a DRO schedule to control for elicitation of social stimulation. Mothers of four 2 1/2- to 3-month-old infants provided social reinforcement for their infants' vocalization under two schedules: continuous reinforcement (CRF) and differential reinforcement of other-than-vocalization (DRO). In a repeated-reversal single-subject experimental design, all four infants produced systematically higher vocalization rates during CRF, even though densities of social stimulation during DRO were equal to or greater than densities provided during CRF. Thus, whatever its elicitation value, social stimulation may reinforce infant vocalization rates.