How the brain deals you a poor hand
June 24th 2010 06:20
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From: New Scientist
IF YOU thought you knew your hand... like the back of your hand, you could be disappointed. Our mental image of the size and position of our hands seems not to match with reality.
Instead, our brains have inner representations that perceive the hand as wider than it really is, and with stubbier fingers.
Matthew Longo and Patrick Haggard of University College London asked volunteers to point to the tips and bases of the fingers of one hand while it was hidden beneath a board. The researchers used an overhead camera to record the guessed positions, then compared these with the dimensions of the real hand.
On average, volunteers estimated that their hands were two-thirds wider than in reality, and their fingers a third shorter (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1003483107).
The most accurate representations were of the thumb and index finger. Longo says this is not surprising, since these are the digits with the highest tactile sensitivity, and larger regions of the brain are devoted to their use.
The researchers say the findings may help in understanding the basis of conditions associated with body dysmorphia, such as anorexia nervosa. "The distortions we have identified may contribute to this," Longo says. "The brain regions responsible may have undue influence on body image perception."
Longo hopes to investigate this further by studying perceptions of face, foot and belly size.
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