Auditory Cues Influence the Rubber-Hand Illusion

The perception of one's own body depends on the dynamic integration of signals from different sensory modalities. Earlier studies have shown that visual, tactile, and proprioceptive information contributes to this process. However, little is known about the role of auditory cues in the multisensory integration of bodily signals. To address this issue, we studied the effect of auditory feedback on the rubber-hand illusion and the somatic version of this illusion. In each experiment, we tested 30 healthy participants using four different conditions: synchronous touches without auditory cues (original illusion), asynchronous touches without auditory cues (original control), synchronous touches with synchronous auditory cues (illusion positively modulated by sound), and synchronous touches with asynchronous auditory cues (illusion negatively modulated by sound). For the classic rubber-hand illusion, we found that synchronous auditory cues made the illusion stronger compared with asynchronous auditory cues, as evidenced by both the results of the questionnaires and proprioceptive drift. In both versions of the illusion, proprioceptive drift indicated that the synchronous auditory cues enhanced the illusion compared with the condition without auditory feedback and that the asynchronous auditory cues reduced the illusion compared with the nonauditory condition. Taken together, these results demonstrate that auditory cues modulate the rubber-hand illusion, which suggests that auditory information is used in the formation of the coherent multisensory representation of one's own body. Public Significance Statement This study highlights the importance of sounds in the perception of our own bodies by demonstrating that auditory feedback modulates a classic perceptual illusion, the so-called "rubber-hand illusion." In the first experiment, we found that sounds of brushstrokes enhanced the illusion that a rubber hand was one's own when presented in synchrony with brushstrokes applied to the visible model hand and to the participant's real hand, which was hidden from view. Similarly, in the second experiment, we found that sounds of finger taps enhanced a nonvisual version of the illusion where the participants touched a right rubber hand with their own left finger while receiving corresponding touches on their real right hand. Taken together, these results are important because they reveal how sounds that the body makes contribute to the perception of what constitutes o