Automatic Speech-Gesture Integration in Autistic Children: The Role of Gesture Semantic Activation

This study investigates whether autistic children exhibit differences in automatic gesture-speech integration (GSI) through an implicit measurement approach and clarifies the potential role of gesture semantic activation in this process. Twenty-one autistic children and 21 age-, verbal-intelligencer-, and nonverbal-intelligencer-matched neurotypical (NT) children participated in the study. (1) A semantic irrelevant task to assess whether autistic children can automatically integrate gestures and speech without requiring semantic processing; (2) a gesture semantic task to examine the impact of active gesture semantic activation on GSI. The experiment incorporated eye-tracking technology to measure reaction times (RTs) and total fixation duration (TFD) on gestures. In Experiment 1, neither RTs nor TFD on gestures in autistic children showed sensitivity to semantic congruence, contrasting with NT children's semantic congruence effects. Nevertheless, autistic children demonstrated markedly reduced TFD on gestures relative to their NT peers. In Experiment 2, autistic children demonstrated semantic congruence effects similar to those of NT children in TFD on gestures, whereas in RTs, such effects were restricted to the gesture-picture congruent condition. This study indicates that autistic children exhibit atypical automatic GSI; however, these differences are attributable to insufficient bottom-up semantic activation rather than inherent deficits in integration abilities. This study offers novel insights into cross-modal semantic processing mechanisms and promotes the development of neurodiversity-based adaptive language intervention strategies.