Why Peter Pan might never empathize with Captain Hook: The sensitivity of the human body schema to hidden, missing, and prosthetic limbs


It has been proposed that our brain stores a representative map of our dynamic body shape in space, known as the body schema that we can use in social cognitive processes such as self-other matching and empathy. One method used to study the body schema and self-other matching involves the body part compatibility task (Bach, Peatfield & Tipper, 2007). This research has shown that when target stimuli are presented on the limbs (e.g., hand) of an observed body, response initiation times are shorter when the response is made with the same limb (e.g., hand) in the observer than when it is made with a different limb (e.g., foot). These data suggest that we identify with the observed body and respond to the stimuli with our own compatible limbs. The purpose of the present experiments was to use the body-part compatibility effect task to assess the coding of observed limbs when observing altered body forms. In Experiment 1, when the target limb (hand) was hidden behind an object (backpack) we observed a body part compatibility effect consistent to a full-limb control suggesting that the observer was able to intuit the limb behind the backpack and match the response compatibility.  In Experiment 2, when the observers viewed stimuli on a non-existent limb (limb amputee) there was a disruption in the body part compatibility effect. Finally, in Experiment 3, when the non-existent amputated limb was extended via a prosthetic limb (that matched the size attributes of a control full-limb body) the body part compatibility effect did not consistently re-emerge.  In sum, the present data suggest that the human body schema is sensitive to modulation depending on the integrity of the human body being observed.

Acknowledgments: This research was supported by grants from NSERC and the Ontario Ministry of Research and Innovation.