Action prediction judgements are unaffected by motor impairment in participants with spinal muscle atrophy


Spinal muscle atrophy (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. It remains unknown whether limited motor experience in participants with SMA impairs their ability to make perceptual judgements about the others' actions. To examine this, participants with SMA and sex and age matched controls (NH) performed a perceptual-motor judgment task using the Fitts's law paradigm (see Fitts, 1954). Participants observed apparent motion videos of reciprocal aiming movements with varying indices of difficulty (ID, see: Manson et al., 2014). For each movement, participants selected the shortest movement time (MT) at which a young adult could perform the task while maintaining accuracy. To index upper limb motor ability participants completed a SMA health index questionnaire (SMAHI) and received a score from 1 (some motor function) to 5 (no motor function). Contrary to our expectation, both groups showed a Fitt's law relationship (e.g., MT linearly increased as ID increased). 10 participants with SMA reported SMAHI scores of 1-3 (some motor function) and 5 reported SMAHI scores of 4.5-5 (no motor function). A supplementary analysis revealed no differences between the participants with some and no motor function. Overall, results suggest that participants with SMA who have none or limited motor experience are still able to make predictions about other peoples' actions. Furthermore, our findings provide evidence that participant's action-prediction judgements may not be biased on their own motor capability.

Acknowledgments: MITACS