Abstract
Infant siblings of children with autism spectrum disorder display differences in early language and social communication skills beginning as early as the first year of life. While environmental influences on early language development are well documented in other infant populations, they have received relatively little attention inside of the infant sibling context. In this study, we analyzed home video diaries collected prospectively as part of a longitudinal study of infant siblings. Infant vowel and consonant-vowel vocalizations and maternal language-promoting and non-promoting verbal responses were scored for 30 infant siblings and 30 low risk control infants at 9 months of age. Analyses evaluated whether infant siblings or their mothers exhibited differences from low risk dyads in vocalization frequency or distribution, and whether mothers' responses were associated with other features of the high risk context. Analyses were conducted with respect to both initial risk group and preliminary outcome classification. Overall, we found no differences in infants' consonant-vowel vocalizations, the frequency of overall maternal utterances, or the distribution of mothers' response types. Both groups of infants produced more vowel than consonant-vowel vocalizations, and both groups of mothers responded to consonant-vowel vocalizations with more language-promoting than non-promoting responses. These results indicate that as a group, mothers of high risk infants provide equally high quality linguistic input to their infants in the first year of life and suggest that impoverished maternal linguistic input does not contribute to high risk infants' initial language difficulties. Implications for intervention strategies are also discussed.