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Grown men swap bodies with virtual girl

Simulated visual shifts create illusion of being in someone else's skin

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4:43pm, May 12, 2010
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Virtual reality can get downright unreal. In this simulated realm, grown men given a new perspective on the world suddenly find themselves convinced that they inhabit the body of a young girl.

Guys who spend time looking at a simulated world through a life-size virtual girl’s eyes feel as if they reside in her body when they then view her from a third-person perspective, say cognitive scientist Mel Slater of University of Barcelona and his colleagues.

This illusion derives from a real-world expectation that a person who looks down will see his or her own body, the researchers propose in a paper published online May 12 in PLoS ONE. In the experiment, men wearing virtual-reality headsets gazed down to see a girl’s body, first at ground level and then from above.

“When subjects looked down they saw a different body, suggesting that this was a powerful cue for the brain to generate the illusion that the virtual body was their own,” Slater says.

He plans to use this phenomenon in future experiments to study the nature of self-awareness and body consciousness. The discovery may also lead to virtual-reality games in which human players actually feel that they’ve switched places with virtual characters.

“It’s especially compelling that such relatively simple manipulations can profoundly alter our sense of reality,” remarks neuroscientist Vilayanur Ramachandran of the University of California, San Diego. He says Slater’s study “is an elegant and important culmination of over a decade of experiments that demonstrate a powerful role of visual input, whether conveyed by mirrors or video, in maintaining and anchoring body image.”

In 2008, another team observed this body-swap illusion in volunteers who adopted a partner’s visual perspective, via a 3-D headset, while shaking hands with that person for about 10 seconds (SN: 12/6/08, p. 16). Slater’s new study provides the first demonstration that changes in visual perspective alone can induce the feeling that another’s body is one’s own.

In the new experiment, 24 men wore stereo headphones and lightweight head-mounted devices over their eyes that allowed them to move through a virtual room. For two minutes, volunteers explored the room, which included a standing woman stroking the shoulder of a seated girl.

Participants then stood with the virtual woman and girl. Half were assigned to continue viewing the room from their own perspective for almost seven minutes. The rest assumed the girl’s perspective, so that when looking down at themselves they would see her body.

The virtual girl moved her head either in or out of time with volunteers’ own head movements. Men in both groups also felt shoulder strokes delivered in or out of sync with the virtual woman’s stroking of the girl’s shoulder.

Participants’ virtual viewpoints were then lifted up toward the ceiling so the men looked down on the girl from a third-person perspective. The woman continued to stroke the girl’s shoulder, but the men felt no shoulder strokes.

Suddenly, the woman slapped the girl’s face three times.

Men who had previously taken the virtual girl’s visual perspective while receiving synchronized shoulder strokes reported having had strong feelings of being inside her skin when the slaps were delivered.

Men who had taken the girl’s perspective also displayed sharper heart-rate declines than men who had not. Alarming events typically trigger this physiological response.

Critically, men who displayed the steepest heart-rate drops during virtual slaps later reported having had especially strong feelings of inhabiting the girl’s body. These men also felt that they were being personally attacked by the woman and that they faced possible physical injury. Such responses show that visual manipulations alone can induce body-swap illusions, the researchers conclude.

Slater suspects that head-mounted devices can be designed to trick players into thinking they have swapped bodies with characters in virtual games. “These devices are beginning to get better, but they’re still not at a level for consumer use,” he says.

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