What Do You Know About Your Body?

When we know somewhere well, we say we “know it like the back of our hand.” But new research has shown that how we think of our hands is wrong.

false impressions

Dr Matthew Longo and his colleagues at the Institute of Cognitive Science at University College London did an experiment. They covered the left hands of 100 people. Then, they asked the people to point to where they thought their fingertip and knuckles were. They made some quite big mistakes.

“People think their hand is wider than it actually is,” says Dr Longo. The fingers appear shorter than they are. The mistake increases as you go across the hand from the thumb to the little finger.

body maps

“It's connected to our sense of position,” explains Dr Longo. This is our ability to tell where different parts of our bodies are, even when we can’t see them. It also tells us whether we are going up or down in a lift. That information comes from signs from nerves in real time. “We also need to know the distance between joints,” he continues. The brain knows the size and shape of our body from the maps it has. “This experiment tried to find those maps.”

under my skin

These mistakes may be due to how the brain understands different parts of the skin.  “Our brains 'see' areas as larger where the skin is more sensitive,”  says Dr Longo. Body parts don’t appear as their true size, but seem bigger or smaller depending on how strongly they feel touch. Our lips, for example, have more nerves than our nose.  So our brain “sees” lips on its map of the body as being bigger than our nose. The same thing happens for other parts of the body which have lots of nerves.

Dr Longo believes that more research in this area may help us to understand eating problems better. People who suffer from anorexia, for example, tend to think that their body is wider than it is. They don’t eat because they think they’re fat.