Learning to coordinate a redundant motor system : the role of postural comfort

Abstract

When realizing a motor goal, actors have access to a large number of redundant action possibilities from which a particular movement must be selected. Comfort has been shown to play an important role in the selection of particular actions and may be important for resolving the redundancy problem. To understand the relationship between comfort and motor redundancy, I asked subjects to perform a novel motor control task involving coordinated arm movements. Using a full-body motion capture system, the angles of six arm joints were mapped onto the position of a cursor in a 2D virtual environment. Subjects moved the cursor between four targets by adopting different arm postures. The mapping between arm posture and cursor position was redundant and unintuitive, presenting a novel redundancy problem to be resolved. Over practice, subjects constrained movements to a subset of motor solutions consistent with more comfortable body postures. A reduction in the overall complexity of movements, and an increase in the similarity between postures adopted was also observed. Taken together, these findings suggest that the comfort of particular motor solutions is important for constraining the set of redundant actions, as well as improving motor performance in a novel motor task.