Reaching patterns across working space: the effects of handedness, task demands, and comfort levels.

Two experiments are reported which examine skill demands, location, and perceived comfort levels for a preferential reaching test with left- and right-handed participants. In Experiment 1, the effect of task demands was examined by having participants perform tasks of varying difficulty with tools (Lift, Pantomime, and Use) that were placed in an array in working space. Preferred hand reaches predominated at the midline and ipsilateral positions, and decreased significantly for contralateral positions, where the frequency of preferred hand reaches increased with task difficulty. In Experiment 2 we developed a new measure (the Comfort Rating Scale) to rate the subjective feeling of comfort for reaching movements. Using the same array of tools and tasks, participants were instructed which hand to use to perform reaching movements, and then rated how the movement felt. The preferred hand was always rated as being comfortable, whereas the non-preferred hand was sensitive to the effects of task demands and tool position. The ratings showed that it was the level of comfort with the non-preferred hand, rather than with the preferred hand, that contributed to the patterns seen on the first study. The Comfort Rating Scale provides new insight into the distribution of reaching movements within working space.