The relative contribution of rhythm, intonation and lexical information to the perception of prosodic disorder

Abstract

Acoustic studies indicate that children with Autism Spectrum Disorder (ASD) produce atypical rhythm and intonation (Diehl & Paul, 2011). Behavioral studies suggest that children with ASD combine prosody with lexical content in atypical ways (Peppé et al., 2007). The current study assessed the relative contribution of rhythm, intonation, and language context to perception of prosodic disorder. Short excerpts were taken from narratives produced by 18 children with ASD and 18 typically developing controls. Prior study indicated that listeners easily distinguished groups on the basis of these excerpts. Here, the excerpts were resynthesized to control for voice quality and to allow for selective inclusion of F0, duration, intensity and lexical information. Experiment 1 investigated listeners' ability to distinguish the groups based on delexicalized samples that preserved only rhythm (duration+intensity), only intonation, or a combination of both. Experiment 2 investigated the contribution of lexical information to the judgments, and the interaction of lexical information with intonation. Results indicated that (1) listeners were less able to distinguish between groups in the Intonation Only condition, and (2) intonation had a negligible effect on performance when lexical content was present. We conclude that rhythm cues and lexical information contribute more to perceived disorder than intonation.