Conversational gestures in autism spectrum disorders: asynchrony but not decreased frequency

Conversational or "co-speech" gestures play an important role in communication, facilitating turntaking, providing visuospatial information, clarifying subtleties of emphasis, and other pragmatic cues. Consistent with other pragmatic language deficits, individuals with autism spectrum disorders (ASD) are said to produce fewer conversational gestures, as specified in many diagnostic measures. Surprisingly, while research shows fewer deictic gestures in young children with ASD, there is a little empirical evidence addressing other forms of gesture. The discrepancy between clinical and empirical observations may reflect impairments unrelated to frequency, such as gesture quality or integration with speech. Adolescents with high-functioning ASD (n = 15), matched on age, gender, and IQ to 15 typically developing (TD) adolescents, completed a narrative task to assess the spontaneous production of speech and gesture. Naïve observers rated the stories for communicative quality. Overall, the ASD group's stories were rated as less clear and engaging. Although utterance and gesture rates were comparable, the ASD group's gestures were less closely synchronized with the co-occurring speech, relative to control participants. This gesture-speech synchrony specifically impacted communicative quality across participants. Furthermore, while story ratings were associated with gesture count in TD adolescents, no such relationship was observed in adolescents with ASD, suggesting that gestures do not amplify communication in this population. Quality ratings were, however, correlated with ASD symptom severity scores, such that participants with fewer ASD symptoms were rated as telling higher quality stories. Implications of these findings are discussed in terms of communication and neuropsychological functioning in ASD.