Gestures and Words in the Early Communication of Infant Siblings of Children with Autism

Background: Numerous studies have documented impairments in language and gesture in children with ASD; and more recent work has begun to describe similar delays in the later-born siblings of children with Autism.

Objectives: This study focused on production of words, non-word vocalizations, deictic gestures (Reach, Give, Show, Point), and conventional representational gestures (e.g., Yes, No, Bye) in Infant Siblings (Sibs) and no-risk comparison infants (NR).

Methods: Twenty-one Infant Siblings (2 of whom were later diagnosed with Autism) and 18 NR infants (all later-borns) participated in this research.  Infants and primary caregivers were videotaped at home for approximately 45 minutes each month between the ages of 5 and 14 months, then at 3-month intervals from 18 to 36 months.  Parents completed the MacArthur-Bates Communicative Development Inventory (CDI) at all observations beginning at 8 months.  Data presented here focus on the 13- and 18-month sessions.

Results: Findings indicated that: a) as a group and at both 13 and 18 months, relative to NR infants, Sibs exhibited broad delays in overall communicativeness (total production of non-word vocalizations, words, and gestures) and significantly fewer words and deictic gestures; b) at 13 but not 18 months, Sibs also had fewer non-word vocalizations; c) at 13 months the two children who later received an Autism diagnosis were at the bottom of the distribution on all variables; and d) at 18 months these children produced very few gestures of any kind and almost no words.  Finally, communication variables at 18 months were significant predictors of 30-month percentile scores on the CDI.

Conclusions: Even at 13 months, variation in gesture and vocalization production may index later diagnostic outcomes.  Findings are discussed in terms of their implications for an understanding of individual differences among Infant Siblings, prediction of future ASD diagnosis, and the Broader Autism Phenotype.