Evolutionary Psychology Co-Editors: Bernhard Fink, Benedict C. Jones, and Todd K. ShackelfordTask selection is critical for the demonstration of reciprocal patterns of sex differences in hand/arm motor control and ear/far visual processing
Evolutionary Psychology 6(2): 342-364Abstract
Women have been reported to perform better with hand rather than arm movements (Sanders and Walsh, 2007) and with visual stimuli in near rather than far space (Sanders, Sinclair and Walsh, 2007). Men performed better with the arm and in far space. These reciprocal patterns of sex differences appear as Muscle*Sex and Space*Sex interactions. We investigated these claims using target cancellation tasks in which task difficulty was manipulated by varying target size or the number of distracters. In Study 1 we did not find the Muscle*Sex or the Space*Sex interaction. We argue that ballistic movement was too simple to reveal the Muscle*Sex interaction. However, a trend for the Space*Sex interaction suggested task difficulty was set too high. Study 2 introduced easier levels of difficulty and the overall Space*Sex interaction narrowly failed to reach significance (p = 0.051). In Study 3 the Space*Sex interaction was significant (p = 0.001). A review of the present, and four previously published, studies indicates that task selection is critical if the Space*Sex interaction and its associated reciprocal within-sex differences are to be demonstrated without the obscuring effects of Space and Difficulty. These sex differences are compatible with predictions from the hunter-gatherer hypothesis. Implications for two-visual-system-models are considered.
Keywords
Sex differences, hand/arm motor control, near/far visual processing, tool use, hunter-gatherer hypothesis, two visual systems.