Difficulties in tool embodiment among individuals with autism spectrum disorder: A virtual reality study

Purpose Individuals with autism spectrum disorder (ASD) have been reported to experience difficulties with tool use. "Tool embodiment" may contribute to skilled tool use, whereby a tool is incorporated into the body representation and perceived as an extension of the body. Individuals with ASD may also have difficulty integrating proprioceptive information with external visual space. However, the characteristics of sensory information integration, including tool embodiment, during tool use remain unclear. We investigated these characteristics using a newly developed tool manipulation task in a controlled virtual reality (VR) environment. Methods Twenty-six adults with ASD and 32 typically developing (TD) adults participated. Participants performed reaching movements toward a target in VR using a short or long rod. We evaluated whether they could accurately reproduce learned reaching movements based on internal body representations, including rod information, without visual feedback of the hand or rod. Results The ASD group showed significantly lower reaching accuracy and stability than the TD group only when the hand and rod were invisible during movement and the rod length was altered between trials (each p < .05). Conclusion The findings suggest differences in the processing, integration, and updating of learned information associated with tool use when visual feedback is unavailable. One possible explanation is difficulty incorporating information about the rod tip into the representation used to guide reaching movements. However, the findings do not provide direct evidence of altered tool embodiment. VR may contribute to understanding the factors underlying sensorimotor atypicalities in ASD and inform future support and training methods.