The limb-specific embodiment of a tool following experience

The present study was designed to investigate the incorporation of tools into the human body schema. Previous research on tool use suggests that through physical interaction with a tool, the representation of the body is adjusted to incorporate or “embody” the tool. The present experiment was conducted to test the limb-specific nature of tool embodiment. Participants were presented with images of a person holding a rake and executed hand- and foot-press responses to colored targets superimposed on the hand, foot, and rake of the image. This task was completed before and after moving a ball around a course with a hand-held rake. Consistent with previous research, a body-part compatibility effect emerged—response times (RTs) were shorter when the responding limb and target location were compatible (e.g., hand responses to targets on the hand) than when they were incompatible (e.g., hand responses to targets on the foot). Of greater theoretical relevance, hand RTs to targets presented on the hand were shorter than those to targets on the rake prior to experience, but were not different after completing the rake task. The post-experience similarity in hand RTs emerged because there was a significant reduction in RTs to targets on the rake following use. There was no significant pre-/post-experience change in hand RTs to targets on the hand or, importantly, for any response executed by the foot. These results provide new evidence that a tool is embodied in a limb-specific manner and is represented within the body schema as if it was an extension of the limb.