Previous studies have found that individuals with limited motor capabilities due to acquired neurological injury (e.g., spinal cord injury and stroke) can make accurate action possibility judgements for neurologically healthy individuals. Previous studies have shown that people with limited motor capabilities may rely on previous motor experience (i.e., pre-injury) when making action possibility judgments for others. In the present study, we examined whether having severely limited previous motor experience from birth, as a consequence of spinal muscle atrophy (SMA), alters the action possibility judgments made for neurologically healthy individuals. Participants with SMA and Neurologically Healthy (NH) sex- and age-matched controls 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 predicted the shortest movement time (MT) at which a neurologically healthy young adult could perform the task while maintaining accuracy. Between-group comparisons revealed that participants with SMA predicted significantly longer MTs compared to controls. Regression analyses revealed that predicted MTs of both NH and SMA participants exhibited a Fitts’s law relationship (i.e., the predicted MTs significantly increased as movement difficulty increased). A supplementary analysis on the SMA group revealed no differences in predicted MTs between the participants with some and no motor function as assessed by the SMA health index. Overall, these results provide evidence that participants with SMA who have limited or no motor experience may make more conservative action possibility judgments for others. Critically, our finding that the pattern of action possibility judgements (e.g., the slopes of the regression lines) were not different between SMA and NH groups provides evidence that limited previous motor experience may not completely impair action possibility judgements.