Body ownership and tactile processing: Effects of bilateral rubber hand illusion on tactile temporal order judgment

In the rubber hand illusion (RHI), individuals perceive a fake hand as their own if an unseen hand and a visible fake hand are stroked simultaneously. We examined how the RHI on either hand influenced the temporal order judgment (TOJ) of bimanual stimulation. In Experiment 1, participants performed TOJ during RHI or non-RHI conditions. When the fake hand was oriented in an anatomically incongruent position (non-RHI condition), the point of subjective simultaneity (PSS) from TOJ showed no difference between the stroke sides. However, during the RHI condition, the PSS tended to shift in the opposite direction to the stroke, resulting in a significant difference between the sides. This implies slower tactile processing in the illusion-affected hand. When participants performed an identical TOJ while watching the fake hand without stroking (Experiment 2), no PSS modulation was found. Our findings suggest the possibility that the RHI attenuates tactile processing, but its magnitude is small.