The Role of Communication Factors in Bolstering Early Speech Production Growth for Young Children with Autism: A Moderation Model

Background: Many children with autism spectrum disorders (ASD) are nonverbal in toddlerhood and preschool years (Anderson et al., 2007), often presenting with delays in gesture production (Iverson & Wozniak, 2007) and joint attention (Wetherby et al., 2007). Previous longitudinal findings have suggested nonverbal IQ is a strong predictor of later language, whereas Fusaroli et al. (2018) demonstrated that expressive language is the stronger predictor when examined with nonverbal IQ. Previous research has also demonstrated that joint attention is a predictor of later language, but primarily with standardized assessments as outcomes (Pickard & Ingersoll, 2015; Yoder et al., 2015). This study provides a unique contribution by including both social communication and early language samples in a moderation model predicting vocabulary growth.

Objectives: This study aimed to identify the unique roles of social communication elements including emotion and eye gaze, communication, and gesture in moderating growth in spoken language production between toddlerhood and pre-school.

Methods: A subset of secondary data collected longitudinally through the Autism Phenome Project (APP,N=55, 42 males, mean age at initial visit=33.9 months, SD=5.5) was utilized. The APP intends to define clinically meaningful ASD subtypes based on behavioral and biological data, specifically evaluating children immediately following ASD diagnosis at age 24-40 months and follow-up evaluations three years later. A simple linear regression analysis was performed for TWT at the age of diagnosis to predict growth in total word types (TWT) three years later. Subsequently, we performed multiple linear regression models incorporating the interaction effects of TWT and Social Composite scale elements from the Communication and Symbolic Behavior Scales, Developmental Profile (CSBS-DP; Wetherby & Prizant, 2002) Behavior Sample Social Composite scores (see Table 1).

Results: TWT at toddlerhood positively predicted TWT at preschool age in a simple linear model. This association remained significant with the addition of Communication scale performance and its interaction with TWT in toddlerhood to the model, suggesting when controlling for performance on the Communication scale and its interaction, an increase in TWT at toddlerhood by one SD above the mean increased TWT in preschool age by 0.714 SDs. The significant interaction suggested a moderator effect impacting toddler vocabulary growth (see Table 2). This was consistent with a significant negative moderation of the linear association between TWT in toddlerhood and preschool age by the performance on the communication scores in toddlerhood. Similarly, Social Composite score in toddlerhood negatively moderated the linear association between TWT in toddlerhood and preschool age. Performance on the Gesture scale and the Emotion and Eye Gaze scale did not significantly moderate this association.

Conclusions: These findings distinguish communication factors including rate, behavior regulation, social interaction, and joint attention as interactional parameters that uniquely explain the strength of relationship between TWT in toddlerhood at preschool age. The positive association between TWT at time of diagnosis and three years later was stronger in children with lower Communication scale scores in toddlerhood. Studies targeting social communication skills should focus on these underlying elements directly since indirect, growth effects in other social communication areas may co-occur.