Abstract
As numerous movement options are available in reaching and grasping, of particular interest are what factors influence an individual’s choice of action. In the current study a preferential reaching task was used to assess the propensity for right handers to select their preferred hand and grasp a coffee mug by the handle in both independent and joint action object manipulation contexts. Mug location (right-space, midline, and left-space) and handle orientation (toward, away, to left, and to right of the participant) varied in four tasks that differed as a function of intention: (1) pick-up (unimanual, independent); (2) pick-up and pour (bimanual, independent); (3) pick-up and pass (unimanual, joint action); and (4) pick-up, pour and pass (bimanual, joint action). In line with previous reports, a right-hand preference for unimanual tasks was observed. Furthermore, extending existing literature to a preferential reaching task, role differentiation between the hands in bimanual tasks (i.e., preferred hand mobilizing, non-preferred hand stabilizing) was displayed. Finally, right-hand selection was greatest in right space, albeit lower in bimanual tasks compared to what is typically reported in unimanual tasks. Findings are attributed to the desire to maximize biomechanical efficiency in reaching. Grasp postures were also observed to reflect consideration of efficiency. More specifically, within independent object manipulation (pick-up; pick-up and pour) participants only grasped the mug by the handle when it afforded a comfortable posture. Furthermore, in joint action (pick-up and pass; pick-up, pour and pass), the confederate was only offered the handle if the intended action of the confederate was similar or required less effort than that of the participant. Together, findings from the current study add to our knowledge of hand and grasp selection in unimanual and bimanual object manipulation, within the context of both independent and joint action tasks.
Highlights
As there are an almost infinite number of options available to complete any given movement, of particular interest are what factors influence an individual’s choice of action
More right-hand selection was displayed in the unimanual tasks compared to the bimanual tasks [pour = 23.22% and pour and pass = 25.29%; F(1.292,54.268) = 48.163, p < 0.001, η2 = 0.534]
Studies of hand selection in unimanual grasping report a preference for the right hand when picking up objects at the midline and in ipsilateral space, where right-handers are more likely to continue with this pattern of hand selection when reaching for objects in contralateral space (e.g., Bishop et al, 1996; Calvert, 1998; Mamolo et al, 2004, 2006; Bryden and Roy, 2006; Carlier et al, 2006)
Summary
As there are an almost infinite number of options available to complete any given movement, of particular interest are what factors influence an individual’s choice of action. When reaching for objects, hand preference is consistently observed to influence hand selection. Hand and Grasp Selection pattern of hand selection when reaching for objects in contralateral space (Bryden et al, 2000, 2011; Gabbard and Rabb, 2000; Bryden and Roy, 2006; Mamolo et al, 2006; Bryden and Huszczynski, 2011). Motor dominance is not the only hypothesis used to explain hand selection. According to the kinaesthetic hypothesis, biomechanical constraints should decrease preferred hand use in contralateral space to limit awkward postures; hand selection will be constrained by object proximity and efficiency of the movement. The hemispheric bias hypothesis indicates that each hand typically performs best in its own region of space due to spatial compatibility (Gabbard and Rabb, 2000)
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