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Vocal and Communicative Development Lab


Most people think that language is a key defining feature of what it is to be human; however, when we consider what evolution operates on, it is not the mode of a particular communication system per se, but rather, the cognitive and perceptual abilities that allow individuals to communicate. Therefore, while there are aspects of the structure of language that differ greatly from animal communication, the cognitive, perceptual and social abilities of individuals in any species is what ultimately allows them to use whatever communication system they have. In both humans and animals, communication develops in the context of social interactions. I am interested in the interrelation between social interactions and communicative development. How do social interactions influence not only vocal development, but also the usage of vocalizations? And, in turn, how do vocalizations influence social interactions?

Some of our participants           


Don't infants just progress through stages of vocal development?

Why look at vocalizing during social interactions?


Many studies of language development have shown that maternal responsiveness to infant behavior and vocalizations during the prelinguistic period of the first year influences the emergence of language milestones in the second year. Until recently, the only proposed mechanism of phonological development during the first year was maternal imitation of vocalizations. Many researchers believe that phonological development simply unfolds due to physiological, physical, and cognitive maturational processes. Research by a former graduate student at Indiana University, Michael Goldstein, showed that social reinforcement influences infant vocal production. Goldstein, West, and King (2003) showed that mothers' positive social feedback to infant vocalizations influenced infant vocal production. Infants who received contingent social feedback produced more developmentally advanced vocalizations than did infants who received the same amount of feedback, but not contingent on their vocalizing.


To follow up on Goldstein, West and King’s study in which maternal responses were experimentally manipulated, we recently completed an investigation of naturally-occurring maternal responses during social interactions to determine whether mothers naturally provide positive social feedback. Mothers responded to their infants’ vocalizations more with vocal responses compared to interactive responses (smiling, gazing at, touching). Mothers’ vocal responses were often in the form of acknowledgements (‘uh-huh’, ‘oh really?’) as if their infant was really saying something, particularly when infants produced consonant-vowel clusters (more developmentally advanced ‘speech-like’ syllabic vocalizations). In addition, mothers imitated consonant-vowel clusters more than vowel-like sounds, whereas mothers responded with more play vocalizations when their infants produced vowel-like sounds (less developmentally advanced vocalizations lacking a consonantal component). Our current research builds on this finding to explore how maternal responsiveness influences communicative development.


We have recently completed a longitudinal study of communicative development. Mothers and infants came into the playroom in the laboratory for half-hour play sessions biweekly over the course of 6 months starting when the infant was 8 months old. Our questions relate to infants’ vocal repertoires and how maternal responses are differentiated to different sounds, and in turn how differentiated maternal responding influences communicative development. Preliminary results indicate that maternal  responsiveness influences infant vocal production and usage. Mothers who responded to their infants’ vocalizations  by attending to their infants’ attentional focus had infants who increased their vocal production and the percentage of vocalizations directed to their mothers at 14 months of age (e.g., graphs below of one subject on the right) compared to infants whose mothers redirected their attention (e.g., graphs below of one subject on the left). We are currently finishing analyses of many other aspects of maternal responsiveness and changes in infant vocal production over the 6 month period from 8 to 14 months.




Vowel-like = vocalization lacking a consonant, less developmentally advanced

Consonant-vowel = vocalization consisting of a consonant-vowel cluster, more developmentally advanced (‘speechlike’).