Bimanual comfort depends on how extreme either hand's posture is, not on which hand is in the more extreme posture.

Although hand preference is one of the best known features of performance, a recent study of object transfer behavior (Coelho, Studenka, & Rosenbaum, J Exp Psychol Human Percept Perform, 40:718-730, 2014) showed that people place greater emphasis on using the hand that avoids extreme joint angles than on using the hand they normally prefer. In the present study, we sought converging evidence for the hypothesis that adopting midrange joint angles by either hand (the preferred-posture hypothesis) is more important than using the preferred hand in particular to adopt midrange joint angles (the preferred-hand hypothesis). We asked participants to hold both of their hands in different orientations and to rate their comfort. Consistent with the preferred-posture hypothesis but contrary to the preferred-hand hypothesis, the bimanual comfort ratings were more strongly affected by how extreme the two hands' postures were than by which of the hands was in the more extreme posture. The data support a theory of action planning, the posture-based motion planning theory, which says that whole-body postural comfort is a key ingredient for physical action planning.