Infant Vocalizations and Early Home Language Environment

Objectives: It is well known that infant-directed speech (IDS) facilitates early language acquisition. There is also growing evidence that adult-directed (ADS) or overheard speech may influence language learning. Given the importance of early language environment in infancy, greater attention must be paid to systematically investigating home language environment as well as relations between language input and infant volubility. The goals of this study were (1) to investigate the amount of IDS and ADS in a naturalistic environment, (2) to examine infant volubility across differing circumstances, and (3) to explore relations between caregiver volubility and infant volubility. Methods: Sixteen caregiver-infant dyads living in Korea participated in the study. Caregiver and infant vocalizations were recorded using all-day LENA (Language ENvironment Analysis) recorders in their homes as part of a longitudinal study. We quantified the number of infant speech-like vocalizations (i.e., protophones). We also estimated the amount of caregiver volubility. Generalized Estimating Equations (GEE) were conducted to address the research questions. Results: Results indicated that caregivers did not constantly talk to their infants. There was a significant difference in infant volubility between the IDS and No IDS circumstances. However, no significant difference was found between the ADS and No ADS circumstances. Infant volubility was found to be highest when caregiver volubility ranged in the middle. Conclusion: This study may support a midrange hypothesis which suggests that midrange interaction is optimal for infant development outcomes.