Men have a far greater appetite for sex and are more attracted to pornography than women are. This is the timeworn stereotype that science has long reinforced. Alfred Kinsey, America’s first prominent sexologist, published in the late 1940s and early 1950s his survey results confirming that men are aroused more easily and often by sexual imagery than women. It made sense, evolutionary psychologists theorized, that women’s erotic pleasure might be tempered by the potential burdens of pregnancy, birth and child rearing — that they would require a deeper emotional connection with a partner to feel turned on than men, whose primal urge is simply procreation. Modern statistics showing that men are still the dominant consumers of online porn seem to support this thinking, as does the fact that men are more prone to hypersexuality, whereas a lack of desire and anorgasmia are more prevalent in women. So it was somewhat surprising when a paper in the prestigious journal P.N.A.S. reported in July that what happens in the brains of female study subjects when they look at sexual imagery is pretty much the same as what happens in the brains of their male counterparts.

The researchers, led by Hamid Noori at the Max Planck Institute for Biological Cybernetics in Germany, weren’t initially interested in exploring sexual behavior. They were trying to find ways to standardize experiments that use functional magnetic resonance imaging (fM.R.I.) to observe how the brain responds to visual stimuli. In order to do that, they needed to compare past studies that used similar methods but returned diverse results. They happened to choose studies in which male and female volunteers looked at sexual imagery, both because doing so tends to generate strong signals in the brain, which would make findings easier to analyze, and because this sort of research has long produced “inconsistent and even contradictory” results, as they note in their paper. Identifying the reasons for such discrepancies might help researchers design better experiments.

A search turned up 61 studies that met Noori’s criteria for inclusion: Healthy adult men and women of different sexual orientations (including bisexual and transgender subjects) who had rated erotic images in terms of how arousing they were. Those participants had then been put in an fM.R.I. scanner — which detects changes in blood flow associated with neuronal activity — and been shown the most arousing images as well as neutral, nonsexualized ones. What Noori’s team found was that image type — whether it was a picture or a video — was the strongest predictor of differences in which parts of the brain became engaged. Unexpectedly, the weakest predictor was the subjects’ biological sex. In other words, when men and women viewed pornographic imagery, the way their brains responded, in the aggregate, was largely the same.

This latter, more provocative finding yielded the paper’s title, “Neural Substrates of Sexual Arousal Are Not Sex Dependent.” Headlines followed, along with controversy in the cognitive neurosciences. Researchers whose work has shown differences between men’s and women’s brains viewing sexual stimuli objected to such generalization. But the purpose of statistically analyzing many studies together, a process called meta-analysis, is precisely to be more conclusive: The goal is to reveal global patterns that smaller studies can’t.