Contingent Maternal Vocal Responses to 9-Month-Old Infant Siblings of Children with Autism

Background: As a group, infant siblings of children with autism demonstrate difficulties in language and communication that appear towards the end of the first year of life (Mitchell et al., 2006; Ozonoff et al., 2014; Paul, Fuerst, Ramsay, Chawarska, & Klin, 2011). These difficulties are presumed to reflect an increased familial risk, but the extent to which this familial risk includes environmental influences remains poorly understood. An extensive literature documenting the role of maternal input in shaping the language development of typically developing infants and toddlers, toddlers with autism, and other high risk infant populations (e.g. infants of depressed mothers), but no studies have examined maternal linguistic input to infant siblings of children with autism in the first year of life.

Objectives: The goal of the current study was to investigate the linguistic input provided to high risk infants by their mothers during the first year of life.

Methods: The vowel (VV) and consonant-vowel (CV) production of 30 infant siblings of children with autism and 30 low risk infants were scored from video diaries filmed in the home when infants were 9 months of age. Maternal contingent responses to these early vocalizations were also scored and classified as either language promoting or non-promoting responses.

Results: A 3 (Diagnostic Group) by 2 (Vocalization Type) repeated measures ANOVA revealed no significant main effects of Group or a Vocalization Type x Group Interaction. There was a significant main effect of Vocalization Type, F(1, 57) = 62.11, p <.001, indicating that infants in all groups produced significantly more Vowel than Consonant-Vowel Vocalizations.

A 2 (Infant Vocalization Type) x 2 (Maternal Response Type) x 2 (Group) repeated measures ANOVA revealed significant main effects of both infant vocalization type, F(1,44) = 9.61, p < .01 and maternal response type, F(1,44) = 61.51, p < .01, with infants overall producing more Vowel than Consonant-Vowel utterances, and mothers overall producing more Language Promoting that Non-Promoting Responses. These main effects were modulated by a significant Infant Vocal Type X Maternal Response Type interaction, F(1,44) = 22.45, p < .01. There were no significant main or interaction effects involving group. Simple main effects analyses conducted to determine the source of this significant interaction revealed that Language Promoting responses occurred significantly more frequently in response to Consonant-Vowel than Vowel vocalizations (F (1, 46) = 21.57, p= .000), while the opposite pattern was observed for Non-Promoting responses, which occurred significantly more in response to Vowels than Consonant-Vowels (F (1,46) = 10.43, p= .002).

Conclusions: 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 will be discussed.