Tools and the Extended Body Representation: Blurred Boundaries between the Models for Perception and Action

The embodiment of tools and rubber hands is believed to involve the modification of 2 separate body representations. Tools are embodied motorically in the body schema following tool use, while rubber hands are embodied perceptually in the body image during the rubber hand illusion (RHI). The embodiment of tools is based in action and requires tool use, while the embodiment of rubber hands is based in perception and requires identification with the rubber hand. Although these processes have been investigated separately in the past, there is evidence that some, but not all, tools can alter the body image. This research examines 3 mechanisms that cause tool-use dependent changes to the body image: tool morpho-functional and sensorimotor match, tool expertise, and tool characteristics such as shape and function. Self-reported identification with the rubber hand was largely unaffected by the tool, but tool-use did impact proprioceptive drift, a behavioral measure of the body image. Proprioceptive drift occurred when the tool had morpho-functional and sensorimotor match, suggesting that this factor may be necessary for a tool-version of the RHI to succeed.