Cross-Modal Generalization of Vocabulary in Children with Autism Spectrum Disorder

Background: Vocabulary is a foundation for many aspects of language and is an important predictor of reading comprehension and later academic success (Dickinson, McCabe, Anastasopoulos, Peisner-Feinberg, & Poe, 2003). Though previous research suggests that children with autism demonstrate deficits in vocabulary in both the receptive and expressive modalities very early in their development (Ellis Weismer, Lord, & Esler, 2010; Luyster & Lord, 2009), the nature of vocabulary deficits involved in this process remains unclear. Researchers have suggested that compared to typically-developing children, children with ASD may acquire partial knowledge of a learned language form and encounter more difficulties generalizing across settings and modalities(Wynn & Smith, 2003). This study aims to investigate receptive and expressive word acquisition and cross-modality generalization in children with ASD.

Objectives: 1) To examine potential differences in word acquisition across receptive and expressive modality in children with ASD; 2) To examine whether children with ASD demonstrate expressive to receptive or receptive to expressive cross-modal generalization of word learning following a combined storybook and play vocabulary intervention.

Methods: A single-subject, multiple-probe design (Wolery, Gast & Hammond, 2010) was implemented to compare vocabulary learned within receptive or expressive vocabulary intervention conditions. Twelve children with ASD between 36 and 90 months were recruited and taught unfamiliar vocabulary in a combined storybook and play intervention (see Table 1 for participants' cognitive, language, and vocabulary ability). For each child, by random assignment, half of the target words were trained expressively and the other half were trained receptively. Probe sessions occurred both before, during, and after each phase of intervention to compare target words learned in the receptive and expressive modality and to probe the extent of cross-modal generalization.

Results: Children learned target words in both receptive and expressive conditions, as evidenced by an average of 80% accuracy across three trials at the end of each intervention. In receptive modality, participants learned target vocabulary to criterion in an average of 10 sessions. In expressive modality, participants learned target vocabulary in 12 sessions on average. Visual analysis of the immediate post-intervention probe condition showed that participants showed considerably greater success generalizing from expressive to receptive modalities. In cross-modal probes, participants identified 79% of the words taught expressively and 46% of the words taught receptively (see Figure 1 & 2 for sample data of successful and unsuccessful cross-modal generalization).

Conclusions: Unlike typically-developing children who are able to generalize vocabulary learned across both receptive and expressive modalities, children with autism in this study were more likely to cross-modal generalize from the expressive to the receptive modality than the opposite direction. Findings from this study provide clinical implication about teaching vocabulary in this population. Specifically, findings showed that vocabulary forms taught receptively will not reliably generalize to the expressive modality. Children with autism may benefit from an intervention focusing primarily on expressive vocabulary which may lead to growth in both the expressive and receptive modalities.