The Impact of Autistic Traits on Prosody and Gesture Perception

Background: The integration of speech and gesture is an essential ability that helps humans to participate in daily communication and social interactions. Various studies support that this integration relates to the development of language and communication. However, deficits in communication and social reciprocity are commonly presented in Autism Spectrum Disorders (ASD) and several studies suggest that individuals with ASD have more difficulty in the integration of speech stimuli as well as in discriminating temporal asynchrony in linguistic and other scenarios. These differences in speech and gesture integration in ASD may impact on social and emotional communication and multisensory temporal integration.

Objectives: To investigate differences of speech-gesture processing between typical individuals and those with high levels of autistic traits using three different stimuli conditions, including auditory, visual, and audio-visual conditions.

Methods: We used a cutoff of above 29 on the Autism Quotient score to enter the High AQ (HAQ) group and below 18 to enter the Low AQ (LAQ) group. The ongoing study involves 24 right-handed individuals (17 LAQ and 7 HAQ) between the ages of 18 and 40 years old. All participants took the WASI to measure IQ. Three experiments were conducted: (1) Experiment 1 investigated performance differences in prosody perception between the two groups with 5 different tasks, (2) Experiment 2 investigated differences in processing gestures between the two groups and (3) Experiment 3 explored differences in the ability to distinguish emotional congruence and incongruence of prosody and gesture and between the two groups.

Stimuli- Two stimuli sets were used in this experiment: (1) From the Egisti et al.(2012) study, emotional (Angry, Neutral) and grammatical (Statement, Question) sentences with audio-only condition and (2) From the Piwek et al.(2015) study, emotional (Angry, Happy, Neutral) sentences in an audio-only condition, point-light displays in a video-only condition, and audio-visual stimuli including two different conditions (emotional congruence and incongruence) were used.

Results: The results of Experiment 1 revealed that there was no difference between LAQ and HAQ groups in prosody perception. However, in one task that involved finding emotional and grammatical prosody together, the HAQ group showed lower accuracy than the LAQ group (p<0.05). Experiment 2 showed that while both groups exhibited low accuracy in correctly perceiving emotions from the gestures (LAQ: 67.7%, HAQ: 56.75%), the LAQ group performed better (p<0.05) than HAQ. In Experiment 3, there was no group difference between LAQ and HAQ to find emotional congruence between auditory and visual stimuli. In overall reaction times, there were no group differences, but both groups showed the slowest reaction times in the gesture-only condition.

Conclusions: This study investigated how autistic traits impact on prosody and gesture perception. Two differences were found in that the HAQ group obtained lower accuracy performance in complex prosody and gesture-only task than the LAQ group. These results emphasise that although both groups performed similarly for several tests, significant performance differences exist between individuals with low and high autistic traits, suggesting that consideration of these differences can help to find how autistic traits impact on social communication.