Sex Differences in Performance with the Hand and Arm in near and Far Space: A Possible Effect of Tool Use

Abstract

Using novel tasks, we tested two predictions from the hunter-gatherer hypothesis concerning sex differences in the motor control of hand and arm and in the visual processing of near and far space. In Study 1 we replicated earlier findings by demonstrating that women scored higher with the hand while men scored higher with the arm. Study 2 tested the motor and visual predictions concurrently and showed that the Muscle*Sex interaction, seen in Study 1, occurs in far as well as near space. However, we failed to confirm that women perform better with visual information from near and men from far space. Instead the relative performance of women and men was the same in far as it was in near space. Drawing on evidence from studies of selective visual neglect we suggest that this outcome arose because tool use causes far space to be re-mapped as near space. Finally, the selective visual neglect literature indicates that the processing of far and near space is located in the ventral and dorsal cortical streams, previously described as two “what”/“where” visual systems. We draw attention to their additional “there”/“here” functions that are sex dimorphic and, as we have shown, modulated by tool use.