New evidence finally reveals how male and female brains really differ

FOR most of recorded history, men and women tended to have different societal roles, interests and occupations. Perhaps it was natural to assume these stemmed from innate differences in their brains, as well as the more obvious ones in their bodies. That idea has long been contentious, but now, with ideas about gender changing faster than ever, the question of whether there are differences between the brains of men and women has taken a keener edge. It remains a divisive issue, even among neuroscientists. Nevertheless, they are finally cutting through the historical discrimination and gender politics to get at the truth.

Early measurements of skull capacity showed that the brains of men are, on average, somewhat bigger and heavier than those of women. Some commentators posited that this “missing 5 ounces” was the key to men’s supposedly superior abilities. In fact, the simple explanation is that bigger bodies require more brain tissue to run them – a relationship seen across animal species.

Things got more complicated with the advent of brain-scanning technology in the 1990s, which suggested sex differences in the size of specific brain regions and structures. These findings were often turned into compelling tales about why, for instance, women are more empathic on average, or why men are more likely to be engineers. However, studies from the early decades of brain-scanning research should be taken with a pinch of salt, says Lise Eliot at Rosalind Franklin University in Illinois. “When you control for brain size, all of the claims about volume differences of individual structures…