Bishop, E G, & DiLalla, L.F. (1994). Differential mother-child interactions in infancy and their effects on infant vocalizations. Poster presented to the Life Span Development Conference, October, Carbondale, IL.

The goal of this study was to increase our understanding of the mechanisms involved in differential mother/infant interactions. This study examined the heritability of vocalization behavior and differential maternal treatment as it impacted on infant vocalizations. Subjects were same-sex infant twin pairs and their mothers who were part of the Twin Infant Project (TIP), a longitudinal study of twins and their parents. From videotaped interactions conducted in the subject’s homes at 7 and 9 months of age, we extracted three behaviors: 1) Verbal Attempts by the mother to get the child to vocalize; 2) Acknowledgments by the mother when the child did vocalize; and 3) Vocalizations by the child. Results indicate some evidence for the heritability of the infant’s vocalizations at 9 months as well as significant correlations between infant’s Vocalizations and mothers Acknowledgments at both ages. These results suggest that: 1) duration of infant vocalizations is heritable at 9 months and is not simply a function of infant environment; and 2) although infants who vocalized more had mothers who more often acknowledged these vocalizations, these children did not necessarily have mothers who attempted to elicit vocalizations more, which might suggest that the direction of effect is from the child to mother, rather than from mother to child.