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How To Master Your Third Arm

How To Master Your Third Arm Popular Science


In the 2002 movie Minority Report, Tom Cruise plays with a futuristic computer like a maestro. With a flick of his wrist, data moves from one screen to the next, and a panoramic view of a park spins like a toy top.

“But if it’s virtual reality, why should he only use two arms? Why should he even have a humanlike form?” asks Jeremy Bailenson, director of Stanford's Virtual Human Interaction Lab.

Last week, Bailenson’s team released new research that shows a person can master a virtual third arm within just a few minutes. The study explores the concept of “homuncular flexibility”, wherein people learn to control bodies different from their own by changing how they perceive human movements.

“It opens interesting opportunities, such as with the design of video game avatars, but could also help war amputees who are in rehab,” says cognitive neuroscientist and media researcher Wijnand IJsselstein, who wasn’t involved with the research.

The project began in the 1980s as a brainchild of Jaron Lanier, the computer science pioneer who coined the term “virtual reality” as well as homuncular flexibility. Back then, he and a few friends built unnatural virtual bodies like a lobster with three arms along each side of its midriff. They would guide these extra limbs by subtle motions, like an elbow twist or bend of the knee.

But fast-forward two decades, and virtual reality experts remained the only ones who could conquer homuncular flexibility.

“When we first tried this with Jaron, most people failed miserably. Only he and others who are gifted spatially and mathematically could power a third hand,” says Bailenson. “But we learned in this study that the key isn’t intellect, but better motion tracking.”

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It would be very cool to have a third arm in virtual reality. 

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