During a full body illusion (FBI), participants experience a change in self-location towards a body that they see in front of them from a third-person perspective and experience touch to originate from this body. Multisensory integration is thought to underlie this illusion. In the present study we tested the redundant signals effect (RSE) as a new objective measure of the illusion that was designed to directly tap into the multisensory integration underlying the illusion. The illusion was induced by an experimenter who stroked and tapped the participant's shoulder and underarm, while participants perceived the touch on the virtual body in front of them via a head-mounted display. Participants performed a speeded detection task, responding to visual stimuli on the virtual body, to tactile stimuli on the real body and to combined (multisensory) visual and tactile stimuli. Analysis of the RSE with a race model inequality test indicated that multisensory integration took place in both the synchronous and the asynchronous condition. This surprising finding suggests that simultaneous bodily stimuli from different (visual and tactile) modalities will be transiently integrated into a multisensory representation even when no illusion is induced. Furthermore, this finding suggests that the RSE is not a suitable objective measure of body illusions. Interestingly however, responses to the unisensory tactile stimuli in the speeded detection task were found to be slower and had a larger variance in the asynchronous condition than in the synchronous condition. The implications of this finding for the literature on body representations are discussed.

中文翻译：

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冗余信号效果和全身错觉：错觉不会影响多感官，但会影响单感觉触觉刺激。

在全身错觉（FBI）期间，参与者会体验到从第三人称视角看向自己面前的身体的自我定位的变化，并体验到源于该身体的触摸。多感官整合被认为是这种错觉的基础。在本研究中，我们测试了冗余信号效应（RSE），将其作为幻觉的一种新的客观指标，旨在直接利用幻觉的多感官整合。幻觉是由一名实验者引起的，该实验者抚摸并轻拍了参与者的肩膀和腋下，而参与者则通过头戴式显示器感知了他们面前虚拟身体的触摸。参与者执行了快速的检测任务，以响应虚拟身体上的视觉刺激，在真实的身体上产生触觉刺激，并结合（多感觉）视觉和触觉刺激。通过种族模型不等式测试对RSE进行的分析表明，在同步和异步条件下都发生了多传感器集成。这一令人惊讶的发现表明，即使不产生幻觉，来自不同（视觉和触觉）方式的同时身体刺激也会瞬间整合到多感官表征中。此外，这一发现表明，RSE并不是对身体错觉的合适客观衡量指标。然而，有趣的是，在异步条件下，对同步感应条件下的单感触觉刺激的响应较慢，并且具有较大的方差。