An illusory sensation of ownership over a surrogate limb or whole body can be induced through specific forms of multisensory stimulation, such as synchronous visuotactile tapping on the hidden real and visible rubber hand in the rubber hand illusion. Such methods have been used to induce ownership over a manikin and a virtual body that substitute the real body, as seen from firstperson perspective, through a head-mounted display. However, the perceptual and behavioral consequences of such transformed body ownership have hardly been explored. In Exp. 1, immersive virtual reality was used to embody 30 adults as a 4-y-old child (condition C), and as an adult body scaled to the same height as the child (condition A), experienced from the first-person perspective, and with virtual and real body movements synchronized. The result was a strong body-ownership illusion equally for C and A. Moreover there was an overestimation of the sizes of objects compared with a nonembodied baseline, which was significantly greater for C compared with A. An implicit association test showed that C resulted in significantly faster reaction times for the classification of self with child-like compared with adult-like attributes. Exp. 2 with an additional 16 participants extinguished the ownership illusion by using visuomotor asynchrony, with all else equal. The size-estimation and implicit association test differences between C and A were also extinguished. We conclude that there are perceptual and probably behavioral correlates of bodyownership illusions that occur as a function of the type of body in which embodiment occurs.body awareness | self consciousness | perceptual illusion H ow would it be to have the body of a child again, and how would this change perception of the world and your attitudes toward yourself and others? In this article we address this question in the context of body-ownership illusions. The issue of how the brain represents the body has been approached extensively in philosophy (1, 2), cognitive neuroscience (3-5), robotics (6, 7), and virtual environments (8,9). It has been demonstrated that it is straightforward to generate the illusion in people that their body has changed (1, 10-16). In particular, immersive virtual reality (IVR) has been used as a compelling way to manipulate and introduce illusions with respect to the body representation of people in terms of structure, size, and morphology. It has been shown that specific types of synchronous multisensory and sensorimotor stimulation can lead to illusory perceptions of body shape, size, and symmetry even when these are very different from the normal body form (17-23). In other words, there have been significant demonstrations that perceptual ownership of a body that may be quite different to your own is possible through particular types of multisensory stimulation.Although previous work has focused on the phenomena of body ownership and explanations for it, here we show that the form of the body, in terms of the relative proportions of head size, trunk, a...

Virtual reality can be used to visually substitute a person's body by a life-sized virtual one. Such embodiment results in a perceptual illusion of body ownership over the virtual body (VB). Previous research has shown that the form of the VB can influence implicit attitudes. In particular, embodying White people in a Black virtual body is associated with an immediate decrease in their implicit racial bias against Black people. We tested whether the reduction in implicit bias lasts for at least 1 week and whether it is enhanced by multiple exposures. Two experiments were carried out with a total of 90 female participants where the virtual body was either Black or White. Participants were required to follow a virtual Tai Chi teacher who was either Asian or European Caucasian. Each participant had 1, 2, or 3 exposures separated by days. Implicit racial bias was measured 1 week before their first exposure and 1 week after their last. The results show that implicit bias decreased more for those with the Black virtual body than the White. There was also some evidence of a general decrease in bias independently of body type for which possible explanations are put forward.

When we carry out an act, we typically attribute the action to ourselves, the sense of agency. Explanations for agency include conscious prior intention to act, followed by observation of the sensory consequences; brain activity that involves the feed-forward prediction of the consequences combined with rapid inverse motor prediction to fine-tune the action in real time; priming where there is, e.g., a prior command to perform the act; a cause (the intention to act) preceding the effect (the results of the action); and commonsense rules of attribution of physical causality satisfied. We describe an experiment where participants falsely attributed an act to themselves under conditions that apparently cannot be explained by these theories. A life-sized virtual body (VB) seen from the firstperson perspective in 3D stereo, as if substituting the real body, was used to induce the illusion of ownership over the VB. Half of the 44 experimental participants experienced VB movements that were synchronous with their own movements (sync), and the other half asynchronous (async). The VB, seen in a mirror, spoke with corresponding lip movements, and for half of the participants this was accompanied by synchronous vibrotactile stimulation on the thyroid cartilage (Von) but this was not so for the other half. Participants experiencing sync misattributed the speaking to themselves and also shifted the fundamental frequency of their later utterances toward the stimulus voice. Von also contributed to these results. We show that these findings can be explained by current theories of agency, provided that the critical role of ownership over the VB is taken into account.agency | body-ownership illusion | rubber-hand illusion | illusory speaking | vibrotactile stimulation T here is growing evidence that the brain does not treat our body as relatively fixed, changing only slowly through time, but that its body representation demonstrates high plasticity. Although this is counter to common sense, a number of findings have shown that simple experimental manipulations can generate the illusion that an external object is part of our body (1, 2), that a plastic manikin (3, 4), and even a body displayed in immersive virtual reality (IVR), is our body (5-7). Furthermore, evidence suggests that such illusions have physiological and psychological consequences. For example, the rubber-hand illusion (RHI), where participants feel a somatic sense of ownership over a rubber hand through synchronous multisensory stimulation on the rubber and corresponding hidden real hand (1), has been shown to lead to a cooling of the real hand (8) as well as an increase in its histamine reactivity (9). The RHI over a black rubber hand can lead to a reduction of implicit racial bias in light-skinned people (10). When light-skinned people have a dark-skinned VB that apparently substitutes their own body, in IVR-as seen directly and in a virtual mirror, and that moves like themselves-they have the illusion that the body is theirs, which also results in a reduction o...