How to distinguish between referent configuration and internal models hypotheses of motor control?: Comment on "Laws of nature that define biological action and perception" by M. Latash

Reaching Movements With Limb-Based Visual Feedback

Reaches in experimental settings are commonly found to be straight. This straightness is robust to physical, but not visual, perturbations. Here, we question whether typical visual feedback contributes to this finding by implicitly promoting straight movements. To do so, we replaced the conventional feedback depicting the hand's location with feedback depicting the limb's orientation. Reaching movements with three different visual feedback conditions were examined. In the final condition, the subject's arm was depicted as two rotating links, and targets were depicted as two links indicating a desired arm posture. We found that by replacing standard cursor feedback, reaches became curved and arched to the target. Our findings further demonstrate that depicted feedback influences movements, and feedback depicting the limb, in particular, may elicit curved reaches.