French researchers have reported that people who use tools may temporarily alter the structure of their self concept and, correspondingly, their brains to accommodate the tool’s shape and capacity. The findings imply that people who use prostheses also reconfigure their perception of their own bodies to accommodate their device.
The team, led by Lucilla Cardinali of France’s National Institute of Health and Medical Research (Inserm), had participants use a pincer-type grasping tool with a handle to repeatedly pick up and set down a small block. After the participants had done so for several minutes, researchers took away the tool and had the participants perform a series of similar tasks. Cardinali’s team found that the participants, when asked to use their own hands to pick up or even touch the block, were significantly less agile than before they had used the tool. Blindfolded participants asked to point to their elbow and fingertip on their tool-using arm also overestimated the length of that arm.
In the June 2009 issue of the journal Current Biology, the team explained, “To control bodily movements, the human brain relies on a somatosensory representation referred to as the body schema…. These findings indicate that tool-use alters the body schema, and also show that what is modified is the somatosensory representation of intrinsic properties of the body morphology.”
Cardinali told the BBC, “This is the first unambiguous and definitive proof that using a tool modifies the representation of our body; previous studies suggested this but never proved it directly.”