Action possibility judgements in people with limited motor capabilities as a result of spinal muscle atrophy


Predictions about the action capabilities of others are thought to be based on a simulation process involving linked perceptual and motor networks. Given the role of motor experience in the formation of these networks, one's own motor capabilities are thought to be the basis of one's perceptual judgments about other's actions. It remains unknown if limitations in one's own motor capabilities affects the accuracy of predictions made for other's actions. To determine if action possibility judgments are affected by one's own motor capabilities, we examined the predictions made by neurologically-healthy (NH) participants and participants with spinal muscle atrophy (SMA) on a perceptual-motor judgment task. SMA is a rare form of muscular dystrophy that affects motor neurons in the brain and spinal cord and causes a severe impairment of voluntary movement. Participants observed apparent motion videos of reciprocal aiming movements with varying indices of difficulty (ID, see Fitts,1954). For each movement, participants selected the shortest movement time (MT) at which a young neurologically-healthy adult could perform the task while maintaining accuracy. Analyses of MTs revealed that, for both NH and participants with SMA, the predicted MTs linearly increased as a function of ID. Also, participants with SMA predicted significantly longer MTs at all IDs than NH participants. Taken together, these results suggest that, although the judgments may be more conservative, participants with severely limited motor function during development can form accurate action possibility judgements for others.

Acknowledgments: MITACS