Task Selection is Critical for the Demonstration of Reciprocal Patterns of Sex Differences in Hand/Arm Motor Control and Near/Far Visual Processing

Abstract

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.