Via Live Science:
The idea that the human brain sees tools as an extension of the body is an old one. Now scientists have some proof that it’s true…. Researchers have long thought that when we use a tool, even for just a few minutes, it changes the way our brain represents the size of our body; the tool becomes a part of what is known in psychology as our body schema. In the new study, researchers reasoned that if one incorporates a used tool into the body schema, his or her subsequent bodily movements should differ when compared to those performed before the tool was used.Indeed, that is exactly what they saw.
After using a mechanical grabber that extended their reach, people behaved as though their arm really was longer, they found. It’s a phenomenon each of us unconsciously experiences every day, the researchers said. The reason you were able to brush your teeth this morning without necessarily looking at your mouth or arm is because your toothbrush was integrated into your brain’s representation of your arm…. The finding, detailed in tomorrow’s issue of the journal Current Biology, help to explain how it is that humans use tools so well.