Social influences on sensorimotor integration of speech production and perception during early vocal learning

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Infants show dramatic changes in their ability to perceive and produce vocal sounds of their native language over the first year of life. Our conceptual framework interprets this plasticity in the context of encoding reward prediction errors that play a role in associative learning. Our studies will test an important mechanistic question: the extent to which linked perceptual and motor learning of speech-like vocalizations in infants with different histories of social-vocal experience is regulated by contingent pairings of babbling with social-vocal reinforcement by caregivers. Contingent pairings of a signal with a reinforcer induce learning of a prediction in models of associative learning. Thus when social-vocal reward by caregivers is contingent on babbling, infants learn that their utterances predict social reinforcement accompanied by mature vocal patterns and begin to produce speech-like forms that emulate the phonological pattern provided by caregivers. We posit that social reinforcement is a potent driver of learning during the earliest stages of vocal development (6-12 months) in infants with typical hearing (TH). In contrast, infants with congenital hearing loss (HL) will have an impoverished history of social-vocal interactions that impair early vocal learning. However, after hearing remediation via a cochlear implant, social-vocal reinforcement will facilitate learning above and beyond gains due to improved hearing levels alone. Aim 1 will test the hypothesis that HL infants are poorer vocal learners because they do not benefit from contingent pairings of babbling with social-vocal reward to the same extent as TH infants. We will compare the ability of infants with TH versus HL to learn to produce new vocal forms based on experimental manipulations: social-vocal reinforcement by caregivers will be either temporally contingent or random with respect to their infants’ babbling. We predict that babbling-contingent social-vocal reinforcement will be less effective in promoting learning of more speech-like patterns in HL infants, despite matching hearing levels between contingent and random-control groups within both HL and TH conditions. Subsequent remediation of hearing via receipt of a cochlear implant will facilitate vocal production learning based on babbling-contingent social-vocal reward. A parallel Aim 2 will test whether degree of learning to produce the new vocal forms in Aim 1 can predict improved perception of those same sounds. If social-reward based learning strengthens integration between perception and production, then contingent training should improve both productive (Aim 1) and perceptual (Aim 2) learning. We predict that contingent reinforcement will induce correlations between production and perception of vocal sounds in TH infants but will exert limited effects in HL infants, with lowest correlations in infants with more limited production learning. Remediation of hearing following cochlear implantation will enable social-vocal reward to strengthen perception-production links as hearing levels improve. These studies are the first to investigate the role of social factors during sensorimotor integration in the context of prediction-error based associative learning.