The Right Arm Likes to be Close

A prior study revealed that the left (vs. right) hemisphere has a visual attentional bias toward the body, a finding that is consistent with the observation that most of the visual cognitive activities performed by the left hemisphere (e.g., reading) take place in proximal (peripersonal) space. In addition, when right-handed people perform bimanual motor tasks their right hand is often held more proximal to the body than their left hand. In this study, we wanted to test the hypothesis that the right hand is also more biased toward the body than is the left hand. Thus, we had blindfolded right-handed subjects attempt to draw straight horizontal lines (at the junction of the transverse and coronal planes), with their left and right hands, on sheets of paper placed in front of them and then measured their deviation from the coronal plane. We found that these subjects' right hands deviated closer to their body than did their left hands. These results support the postulate that in addition to an attentional bias, the left hemisphere-right hand has a proximal motor bias. This bias might account for means by which right-handed people position their hands when using both hands on tools and implements.