The effects of handedness and age on hand role selection in bimanual tasks.

Most tasks performed in everyday life require both hands to perform asymmetric movements. Such tasks require one hand to act as a manipulator and the other hand as a stabiliser, and choosing the hand to perform each role is termed hand role selection. The dominant and non-dominant hand are usually spontaneously assigned as the manipulator and stabiliser, respectively. Both handedness and age are known to affect coordination during bimanual tasks, but their influence on spontaneous hand role selection across a range of tasks is unknown. This study investigated the effects of handedness and age on spontaneous hand role selection during routine bimanual tasks. Fifty healthy adults (mean age = 53, range 19 - 85 years) performed seven bimanual tasks with five repeats each. Participants were naïve to the study's purpose to avoid any influence on their hand role selection. Handedness was determined using the 10-item Edinburgh Handedness Inventory. Hand role selection in each trial was noted to calculate a Preference score out of 35 for each participant. Overall, participants had a strong preference to consistently use their dominant hand as a manipulator across all tasks. Preference to use the dominant hand as a manipulator was task-dependent and correlated positively with handedness, but it did not correlate with age. These results show the degree of handedness, but not age, affects consistency of hand role selection across a range of bimanual task, and that preference to use the dominant hand as a manipulator varies between tasks.