Baby studies

By studying social interaction and learning as it occurs in moment-to-moment interactions, we connect specific mechanisms of perceptual and cognitive development with social influences on the acquisition of speech, words, and language.

Taken together, our studies show that the infant’s social world is a crucial component of the learning process. When studied as a form of social interaction, vocal precursors such as babbling constitute a crucial, formative phase in the development of communication. The social environment is structured by consistent behavior that captures infants’ attention and increases arousal. Infants are active participants in these interactions, creating new patterns of vocalizing that catalyze developmental changes in speech and language.

Our research on socially guided learning of speech, words, and language uses multiple paradigms, including playback of digital stimuli to parents and controlled social feedback to prelinguistic vocalizations.

The major projects in the lab are:

1. Social influences on prelinguistic vocal learning and phonological development. We are finding that infants can learn to produce novel speech patterns if social feedback is both contingent and contains sufficient statistical variability (i.e. multiple exemplars). There are limits, however, to what speech patterns babies can learn. How does social learning and motoric constraints interact? We are currently running studies to find out.

In a series of studies that link prelinguistic vocal learning with early word learning, we are studying the function of object-directed vocalizations (ODVs), which are babbles that are directed at objects. We found that labeling an object contingently on an ODV facilitates learning word-object associations. It seems that ODVs signal a state of focused attention and arousal. ODVs are the auditory equivalent of a furrowed brow. We are currently studying the effects of ODVs on the behavior of caregivers, and the ability of infants to learn from caregivers’ responses to their ODVs. Thus we are elucidating the earliest social interactions that support the association of sounds and referents.

2. Longitudinal studies of vocal learning over the first year. We recently found that 5-month-olds have learned that their early non-cry vocalizations are effective on adults, and the strength of this early learning predicts language comprehension at 13 months. Five-month-olds don’t change the form of their babbling like the 9-month-olds do, but they will increase the amount of babbling if a social partner stops responding. We are currently running a longitudinal study to assess relations between vocal learning in 5-month-olds, the more advanced forms of vocal learning in 9-month-olds, and language development in the second year. We are also using non-social learning tasks to see if the ability to learn from social feedback is grounded in more general learning mechanisms.

3. Investigations of caregiver responsiveness to infant babbling. In a series of studies, we play back prerecorded (and carefully controlled) infant behavior to adults, to determine the role of caregiving experience, infant vocalizations, and context (e.g. the presence of a toy) on adult responsiveness to infant behavior. We are planning many additional playback studies to look at caregiver responsiveness as it develops across the birth transition and with additional caregiving experience. We are also planning studies that would validate the computer-based playback paradigm with measures of caregiver responsiveness when interacting with their own infants.

4. Caregiver behaviors that facilitate vocal turn-taking with prelinguistic infants. The number of vocal turn-taking infants experience in caregiver-infant interactions predicts their socio-emotional and language development. However, it is unclear what caregiver behaviors elicit infant babbling and provide opportunities to extend the vocal exchanges. This study investigates the effect of caregiver responses to babbling, especially the modalities of caregiver responses, on the dynamics of caregiver-infant turn-taking bouts.

5. The reward value of infant-directed speech. Although infants’ preference for infant-directed speech has been consistently found, the underlying mechanism for this preference remains unclear. This study applies curiosity-driven learning and tests whether infants’ preference for infant-directed speech is driven by its reward value.  Moreover, we use a conditioned place preference paradigm, for the first time with human infants, to measure infant preference for a context.

6. Investigations on the development of infant-directed speech by studying children’s interactions with their baby brothers and sisters. Does infant-directed speech develop over time or do we talk to immature social partners in that style automatically? This study examines how children speak to their infant sibling and adults to determine the nature of children’s infant-directed speech and whether we can observe differences over developmental time. Children engage in three tasks: free play with their infant sibling, responding to playback of pre-recorded infant behavior, and a perspective-taking task. Their parents also engage in free play and the playback task so we can assess the role of social modeling on children’s infant-directed behaviors.