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Study proves that brain views tools as body parts

European researchers have demonstrated that when we use a tool, our brains temporarily think of them as body parts. The findings help to explain why humans are so adept at using tools. The study, published in the journal Current Biology, was partly funded by a mobility grant...

European researchers have demonstrated that when we use a tool, our brains temporarily think of them as body parts. The findings help to explain why humans are so adept at using tools. The study, published in the journal Current Biology, was partly funded by a mobility grant from the EU. Although the idea that the brain incorporates tools into its view of the body (the 'body schema') is almost a century old, this is the first scientific proof that it happens. 'Since the origin of the concept of body schema, the idea of its functional plasticity has always been taken for granted, even if no direct evidence has been provided until now,' commented Alessandro Farnè of the French National Institute of Health and Medical Research (INSERM). 'Our series of experiments provides the first, definitive demonstration that this century-old intuition is true.' The shape of our bodies is not constant, yet our ability to move our limbs and grasp objects does not change as we grow and develop. This is because our brain is constantly updating its representation of the size, shape and position of the different parts of our body. It is widely accepted that when we use a tool, the brain adapts its representation of the body accordingly. For example, we don't need to look at our mouth or arm while brushing our teeth because the toothbrush is incorporated into the brain's representation of the arm. However, until now, direct proof of this idea was lacking. In this study, volunteers were first asked to point to and pick up objects placed on a table with their bare hands. The volunteers were then provided with a 40-cm-long mechanical grabber, which they used to pick up the object on the table. Next, they were asked to pick up the object with their bare hands. Finally, the volunteers were touched at different points on the arm and hand and asked to point to the position above the arm where they had been touched. The results showed that for a short period after using the grabber, the volunteers really behaved as if their arms were longer. Although they were actually able to grasp the object with their bare hands during this period, they did not move their hands as quickly and took longer to complete the tasks. Furthermore, they perceived the places where they had been touched on their arm as being further apart than they really were. 'We believe this ability of our body representation to functionally adapt to incorporate tools is the fundamental basis of skilful tool use,' said Lucilla Cardinali, also of INSERM. 'Once the tool is incorporated in the body schema, it can be manoeuvred and controlled as if it were a body part itself.'

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