Hand study reveals brain’s distorted body model

Our brains contain a highly distorted model of our own bodies, according to new research by BBSRC-funded scientists at University College London (UCL). The findings may be relevant to psychiatric conditions involving body image, such as anorexia nervosa.

A study published yesterday, which focussed on the brain's representation of the hand, found that our model of our bodies is out of synch with reality - with a strong tendency to think that the hands are shorter and fatter than their true shape.

The results of the study, published in the journal Proceedings of the National Academy of Sciences, show that the brain maintains a model of the hand in which our fingers are perceived to be shorter and our hands fatter than they are. Neuroscientists suspect the reason for these distortions may lie in the way the brain receives information from different regions of the skin.

Dr Matthew Longo, lead author from the UCL Institute of Cognitive Neuroscience, said, "The phrase "I know the town like the back of my hand" suggests that we have near-perfect knowledge of the size and position of our own body parts but these results show that this is far from being the case."

"Our results show dramatic distortions of hand shape, which were highly consistent across participants. The hand appears to be represented as wider than it actually is and the fingers as shorter than they actually are - a finding that might also apply to other parts of the body," added Dr Longo.

Participants in the study were asked to put their left hands palm down under a board and judge the location of the covered hand's knuckles and fingertips by pointing to where they perceived each of these landmarks to be. A camera situated above the experiment recorded where the participant pointed. By putting together the locations of all the landmarks, the researchers reconstructed the brain's model of the hand, and revealed its striking distortions.