Males' Superior Spatial Ability Likely Is Not an Evolutionary Adaptation; Testosterone 'Side Effect'?

Feb. 19, 2013 — Males and females differ in a lot of traits (besides the obvious ones) and some evolutionary psychologists have proposed hypotheses to explain why. Some argue, for example, that males' slight, but significant, superiority in spatial navigation over females -- a phenomenon demonstrated repeatedly in many species, including humans -- is probably "adaptive," meaning that over the course of evolutionary history the trait gave males an advantage that led them to have more offspring than their peers.

A new analysis published in The Quarterly Review of Biology found no support for this hypothesis. The researchers, led by University of Illinois psychology professor Justin Rhodes, looked at 35 studies that included data about the territorial ranges and spatial abilities of 11 species of animals: cuttlefish, deer mice, horses, humans, laboratory mice, meadow voles, pine voles, prairie voles, rats, rhesus macaques and talastuco-tucos (a type of burrowing rodent). Rhodes and his colleagues found that in eight out of 11 species, males demonstrated moderately superior spatial skills to their female counterparts, regardless of the size of their territories or the extent to which males ranged farther than females of the same species.

The findings lend support to an often-overlooked hypothesis, Rhodes said. The average superiority of males over females in spatial navigation may just be a "side effect" of testosterone, he said. (Previous studies have shown that women who take testosterone tend to see an improvement in their spatial navigation skills, he said.)

Continued:  http://www.sciencedaily.com/releases/2013/02/130219121345.htm