In sync or not in sync? Illusory body ownership in autism spectrum disorder

Background: A fundamental aspect of self-consciousness is body ownership, which refers to the experience that our body and its parts belong to us and it is distinct from those of other persons. Body ownership depends on the integration of different sensory stimulations and it is crucial for the development of functional motor and social abilities, which are compromised in individuals with autism spectrum disorder (ASD). Here we examined the multisensory nature of body ownership in individuals with ASD by using a procedure based on tactile conflicts, namely the numbness illusion (NI). Method: We induced an illusory feeling of numbness and ownership for another person’s finger by asking participants to hold their palm against another person’s palm and to stroke the two joined index fingers with the index and thumb of their other hand. Results: As expected, when the agent self-strokes their finger, healthy participants do not perceive the NI if the stroking is performed asynchronously. Conversely, in individuals with ASD the illusion occurred with both synchronous and asynchronous self-stroking. Conclusions: We contend that individuals with ASD are more vulnerable than controls to this illusory tactile experience and we discuss the findings in light of impaired perception of the temporal relationships between tactile and proprioceptive inputs.