Demonstration of plastic body schema by tool use.

Cardinali et al have volunteers use a mechanical grabbing arm that extends reach by 40 centi-meters. Measuring arm movements with a high-resolution motion-tracking system, they show that the volunteers reduce the velocity and acceleration of movements to grab or point at an object after a period of using the tool.

When blindfolded, the volunteers also estimate their arms to be slightly longer after tool use, confirming that our body schema — the sense of where our body parts are in space — is plastic.