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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冗余信号效应和全身错觉：错觉影响的不是多感官刺激，而是单感觉触觉刺激。


在全身幻觉（FBI）期间，参与者会体验到从第三人称视角看到的身体的自我定位变化，并体验到源自该身体的触摸。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）作为错觉的一种新的客观测量方法，旨在直接利用错觉背后的多感官整合。这种错觉是由实验者抚摸并轻敲参与者的肩膀和腋下引起的，而参与者通过头戴式显示器感知到他们面前的虚拟身体上的触摸。参与者执行快速检测任务，对虚拟身体上的视觉刺激、真实身体上的触觉刺激以及组合（多感官）视觉和触觉刺激做出反应。通过竞赛模型不等式测试对 RSE 进行分析表明，同步和异步条件下都发生了多感官整合。这一令人惊讶的发现表明，即使没有引起错觉，来自不同（视觉和触觉）方式的同时身体刺激也会短暂地整合到多感官表征中。此外，这一发现表明 RSE 并不是身体错觉的合适客观衡量标准。然而有趣的是，在快速检测任务中，对单感觉触觉刺激的响应被发现比同步条件下更慢，并且在异步条件下具有更大的方差。讨论了这一发现对身体表征文献的影响。