Thursday, May 20, 2010

A virtual slap in the face (isn't there an iPhone app for that?)

This post was chosen as an Editor's Selection for ResearchBlogging.orgResearchers from the group who recently reported the illusion of owning a virtual hand have come out with a new study on the sense of body ownership that has garnered media attention.

The study, conducted by Mel Slater and colleagues, is summarized as follows at

Male volunteers donned virtual reality goggles and took on the view of a virtual teenage girl sitting in a living room. The virtual girl's mother appeared to stroke her shoulder at the same time a real lab assistant stroked the shoulders of the volunteers.
Suddenly, the virtual mother slapped her daughter about the face three times with accompanying sound effects. The male volunteers all experienced a strong bodily reaction measured as rapid deceleration of their heart rates in response to the sudden threat, because they reacted to the virtual slap as if it were real.

...[The researchers] showed that a first-person perspective seems to play the biggest role in helping people inhabit a virtual body. When participants had more of a third-person perspective of the girl-slap (they didn't feel like they inhabited the girl's body), they didn't show the same physiological reactions.
This is pretty cool, but the findings just confirm what all hardcore video gamers already know. ‘First person shooter’ games are largely successful because they make players feel like they are actually part of the warzone displayed on the screen. Gamers would probably report similar feelings of body transfer if they were administered the questionnaires given to subjects in this experiment, and if you’ve ever played a first-person perspective video game, you’ve probably experienced fluctuations in your heart rate when being threatened by enemies.

News reports on this study are calling it a demonstration of an out-of-body experience, but whether the findings should be considered in such a way is up for debate. An out-of-body experience is often defined as the experience in which a person who is awake sees his or her body from a location outside the physical body. A 2007 study by H. Henrik Ehrsson, published in Science, demonstrates a much more convincing induction of an out-of-body experience. In this study, subjects wore head-mounted video displays that showed them a live film recorded by video cameras behind the subjects. Subjects thus observed their own backs from the perspective of someone sitting behind, and they reported experiences of being outside their own bodies and observing themselves.

So the new study by Slater and colleagues on virtual reality and the sense of body ownership is not necessarily a vivid demonstration of an out-of-body experience. Furthermore, the ‘slap-in-the-face’ design and the transfer of male body ownership to a virtual female that make interesting headlines (including the title of this article) are not the significant parts of the study. If this study is to make an impact on future work, it will be its introduction of the first-person video game (or ‘immersive virtual reality’) paradigm to research on the concept of self-consciousness.

The study importantly demonstrates that the sense of body ownership is more dependent on visual perspective (e.g. first-person or third-person) than it is on sensations of touch and movement. Combining this design with neuroimaging and neurophysiology techniques may prove useful in the development of technologies that use virtual reality for brain training therapeutic strategies in cases of neurological disorders and/or injuries and amputations. We’re currently far away from these sorts of applications, but at least the door to immersive virtual reality in neuroscience research is now open.


Mel Slater, Bernhard Spanlang, Maria V. Sanchez-Vives, Olaf Blanke (2010). First Person Experience of Body Transfer in Virtual Reality PLoS ONE

Ehrsson HH (2007). The experimental induction of out-of-body experiences. Science (New York, N.Y.), 317 (5841) PMID: 17717177

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