The Role of Early Social Motivation in Explaining Variability in Useful Speech in Young Children with ASD

Background: Abundant research has confirmed that children with ASD show deficits in both expressive and receptive vocabulary early in their development. However, the mechanisms that contribute to early language learning difficulties remain poorly understood. Social motivation may lead to relatively more processing of input which leads to more receptive language, which in turn, provides the semantic basis for expressive language.

Objectives: We tested the extent to which receptive language level measured at the mid-point of a 12-month intervention mediated the pathway from baseline, pre-intervention, social motivation to expressive language level at the end-point of the study.

Methods: Seventy children with ASD between 15 and 30 months from a larger longitudinal randomized study of intensive treatment for toddlers with ASD were included in the current study. Seventeen participants from the larger study were excluded due to missing data. The larger study evaluates the effects of intervention intensity and style on the developmental quotients of young children with ASD. Social motivation at study entry was measured by the Social Approach subtest raw score from the Pervasive Developmental Disorder Behavioral Inventory (Cohen & Sudhalter, 1999). Receptive language level was measured 6 months after study entry (mid-point) and expressive language was measured 1 year after study entry using age equivalency scores from the Mullen Scales of Early Learning (Mullen, 1995).

Results: The confidence interval for the indirect effect of initial social motivation on endpoint expressive age equivalency score through midpoint receptive language excluded zero, and therefore, is significant (unstandardized ab = 0.1058, 95% CI = [.0090, .1990]; see Table 1 and Figure 1). Style or intensity of treatment did not moderate the mediated effect of mid-point receptive language on the association between baseline social motivation and end-point expressive language (all ps > .05).

Conclusions: The findings support the hypothesis that mid-point receptive language partially explains the association between early social motivation and later useful speech. This is consistent with an input-processing deficit explanation of language deficits in children with ASD. Future work will assess whether this mediated association occurs because social motivation leads to communication that elicits more input or whether social motivation leads to more processing of existing input. Both could explain an association between social motivation and receptive language (i.e., the a path of the indirect association).