The team puts this advantage down to neuron development in the visual cortex, which is boosted by masculine hormones. Since males are flush with testosterone, in particular, they're born with 25 percent more neurons in this brain region than females, the team noted.Evolution at Work?The vision findings support the so-called hunter-gatherer hypothesis, which argues that the sexes evolved distinct psychological abilities to fit their prehistoric roles, the team says. (See "Sex-Based Roles Gave Modern Humans an Edge, Study Says.")Noting that men in the study showed "significantly greater sensitivity for fine detail and for rapidly moving stimuli," the researchers write that their hunter forebears "would have to detect possible predators or prey from afar and also identify and categorize these objects more easily."Meanwhile, the vision of female "gatherers" may have become better adapted recognizing close-at-hand, static objects such as wild berries.John Barbur, professor of optics and visual science at City University London, noted that females are often "worse off in terms of absolute chromatic [color] sensitivity than males."But when it comes to noticing subtle differences among shades of a color, women do tend to come out on top, as they did in Abramov's experiments, said Barbur, who wasn't part of the new study."If you're not dealing with the absolute sensitivity for color detection but the way in which colors are judged—such as the ability to describe a color, or what that color means, and so on," he said, "I'd say that females are definitely much better than males."