This is a variant on the rubber hand illusion that creates the peculiar sensation of having three arms, a bit like Zaphod Beeblebrox in the The Hitchhiker's Guide to the Galaxy. Set up the rubber hand illusion as normal (see box, far top-right) but with two rubber hands on the table instead of one. Get someone to stroke and tap both rubber hands and your unseen hand in the same way. "A lot of people feel the touch on both rubber hands and that their hand is in two places at once," says Ehrsson. "We interpret this as the brain saying 'is that my hand, or is that myrnhand?' It can't make up its mind."
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