Gesture and Language Development in Infant Siblings of Children with ASD

Background:

Deficits in gestural communication are often observed in children with autism spectrum disorders (ASD) and are a central component in the ASD diagnostic criteria. Early communication delays have also been observed in the infant siblings of children with autism who are at heightened biological risk for ASD (High-risk, HR).  Research with expressive language finds increased risk for delays in HR infants both with and without a subsequent ASD diagnosis. However, there is also within-group and between-group variability such that HR children with ASD exhibit more pronounced delays than those with no diagnosis. What remains unclear is whether similar patterns of variability are observed in another aspect of communication—gesture production. We focus on gesture because it is tightly linked to lexical development in typically developing (TD) and atypically developing children, with early gesture predicting concurrent as well as subsequent lexical skill.

Objectives:

Objectives are to: (1) Characterize gesture use in pre-school age HR infants (both with and without a subsequent ASD diagnosis) and (2) investigate concurrent and predictive relations between gesture use and expressive vocabulary.

Methods:

We investigated communication longitudinally in 23 HR infants at 2- and 3-years-of-age. Three HR infants were given an ASD diagnosis at a 3-year evaluation. At 2-years, we coded spontaneous communicative gesture production during semi-structured 15-minute parent-child free-play. We coded both amount and kind of gesture, resulting in two measures: (a) total number of gestures produced and (b) proportion of gestures that are pointing gestures. At 2- and 3-years parents completed a standardized language measure (MacArthur-Bates Communicative Development Inventory; CDI). We used the CDI vocabulary production checklist as our measure of expressive vocabulary.

Results:

Objective 1: Regarding total number of gestures, HR infants produced an average of 10 gestures (range=1-27, SD=7.6). When restricting analyses to HR infants without a known ASD diagnosis (HR-noASD), results were similar (range=1-27, mean=11, SD=8.1). Regarding pointing gestures, a small proportion of gestures were points for both the full HR group and the HR-noASD subgroup (HR mean=.31, SD=.21; HR-noASD mean=.31, SD=.20) with an average of 4 (SD=3.7) and 3.9 (SD=3.9) pointing gestures produced by HR and HR-noASD groups, respectively. Objective 2: Consistent with previous research, HR infants fell at the low end of the typical range at both 2- and 3-years-of-age (Binomial tests: percent below 15^th percentile, p<.01). Further, Spearman correlations revealed that 2-year gesture positively related to 2-year CDI expressive vocabulary (total number of gestures: rho=.47, p<.05; proportion of gestures that are points: rho= p<.52, p<.05). Total number of gestures at 2-years positively (though not significantly) related to 3-year CDI (rho=.38, p<.10), proportion of gestures that were points did not (rho=.14, p<.56).

Conclusions:

We observed large individual differences in HR infants’ total communicative gesture production and relative frequency of pointing gestures. However, on average, both are smaller than what is often reported for TD 2-year-olds. Further, 2-year gesturing related to concurrent expressive vocabulary. Communicative gesture use at pre-school-age is variable among HR infants, and these individual differences relate to variability in expressive vocabulary.