Adaptive body schema for robotic tool-use

The development and expression of many higher level cognitive functions, such as imitation, spatial perception, and tool-use relies on a multi-modal representation of the body known as the body schema. Although many studies support the hypothesis that the body schema is adaptive and alterable throughout ontogenetic development, the mechanisms underlying its plasticity have yet to be clarified. Here we argue that the temporal integration of multisensory information is a plausible candidate mechanism to explain how manipulated objects (e.g. tools) can become incorporated into the body schema. To demonstrate the validity of our idea, we introduce a model of body schema adaptation instantiated in a small-sized, table-top, tool-using humanoid. The robot’s task is to learn to reach for and touch a visually salient distant object, first with its “bare” hand, and then— using the acquired know-how—with a reach-extending tool (a stick). Our experimental results show that in order to successfully causally relate and integrate vision, touch and proprioception, and to learn to use the tool, timing is of crucial relevance. On a more general note, this study also suggests that synthetic modeling might not only be a valid avenue towards getting a better grasp on results provided by neuropsychology and neurophysiology, but also a powerful approach for building advanced tool-using robots.