Infant vocal learning and development is embedded in a social feedback loop. Babbling vocalizations catalyze consistent responding by caregivers, and these predictable social reactions provide opportunities for infant learning. Naturalistic data and experimental manipulations have verified both the potency of babbling for eliciting social-vocal responses from caregivers, and the efficacy of social feedback for rapid advances in infant vocal learning. The impact of infant hearing loss, however, has never been studied with regard to the social feedback loop. Infants born with significant sensorineural hearing loss may be deprived not only of early auditory experience but of social experience as well. The reduction or elimination of social feedback to immature vocalizations, either by reduced or unpredictable parental responses or by infants' lessened ability to perceive those responses, is likely to have strong effects on learning and development of speech. Restoring hearing via cochlear implants improves auditory perception but does not remediate lost social learning opportunities or provide knowledge of how to learn from social partners. The goal of this project is to investigate how social interactions mediate the ability to incorporate phonological patterns of the language environment into vocal repertoires in infants with typical hearing versus infants with hearing loss (who either continue with hearing aids or experience gains in hearing via receipt of a cochlear implant). The investigators' method is to remotely observe naturally-occurring interactions between infants and a parent while recording their vocalizations; the investigators instruct the parent via headphones to provide vocal-social reinforcement to the infants when they produce a babbling utterance. Infant-parent dyads in a yoked control condition receive the same schedule of social reinforcement cues as a matched pair, which is random with respect to actual infant utterances in the control condition.
The goal of this study is to investigate the role of social factors on speech learning, including production and perception, in infants ranging in age from ~7-18 months. Infants have either typical hearing or sensorineural hearing loss. The main prediction of the study is that social reinforcement will engender improvements in vocal learning above and beyond gains in hearing in infants with hearing loss. As part of this study:~The parent and infant engage in a free play session in the playroom while the investigator cues the parent to say simple nonsense words;~Infants hear playback of the same words during a second phase.