Receptive and expressive lexical stress in adolescents with autism.

Lexical stress abilities were investigated in individuals with autism spectrum disorder (ASD) compared to typically developing (TD) controls. We hypothesised that individuals with ASD would demonstrate atypical prosody on lexical and phrase stress tasks and are perceived by listeners as sounding unnatural. A between-group study was conducted to investigate lexical stress abilities among adolescents (12-20 years) with ASD ( = 11) compared to TD controls ( = 11) matched for age and gender. Two tasks were administered to assess the ability to receptively and expressively distinguish nouns from verbs and a noun phrase from a compound noun. Receptive tasks required participants to select visual stimuli corresponding with the utterance they heard. Expressive tasks were rated using perceptual judgments of accuracy, perceptual and acoustic measurements of duration and perceptual ratings of "naturalness." Individuals with ASD performed with significantly less accuracy on all prosody tasks, significantly longer duration of utterances, and were rated as sounding "unnatural" at a significantly higher rate than controls. This study provides converging evidence that supports atypical prosody is influenced by longer duration of utterances and less accurate lexical and phrase stress. The clinical implications of this study support early assessment and intervention of prosodic disorders in ASD.