A kinematic examination of hand perception

Previous research has found that the perception of our hands is inaccurate. This distorted representation has several constant characteristics including an overestimation of hand width and an underestimation of finger length. In this study, we further investigate this phenomenon by exploring the boundaries of hand representation. Participants placed one hand underneath a table top so it was occluded from view. Using their free hand, participants were instructed to point to the location where they believed the tips and bases of each of their fingers were. These ten landmarks were recorded using a motion capture system. One group of participants pointed to the landmarks in a random order (as done in previous studies) while another group pointed to them in a systematic fashion (from the tip of the thumb sequentially through to the pinky). Furthermore, to explore if having a frame of reference facilitates hand perception, some participants initiated each of their estimations directly from the previous landmark while others initiated them from a home spot located outside the span of the hand. Results showed that the participants who pointed in the systematic order made numerous accurate judgments of hand size and were overall more precise than participants who pointed in a random order. Including a frame of reference however, had no effect on the judgments. The results also showed asymmetries in hand perception. These findings are discussed in relation to different possible internal body representations and hemispheric asymmetries in body perception.