A Binary is a Wonderful Thing to Break: New Study Rejects the Idea of “Male” and “Female” Brains

Illustration by Aimee Chang

We explored this topic—in part—because a Bitch reader asked us to look into it. Got a question about feminism and pop culture that you want answered, too? Tell us! 

I have a good friend with whom I often talk about politics and culture. He’s a lovely, kind person with a deep commitment to social justice and an unfortunate tendency to mansplain. He knows this, and is trying to work on it, so we developed a sort of code. Whenever he starts mansplaining, I just say, “Ow! My ladybrain!” It’s good-natured ribbing that gets the point across, but it also winkingly refers to ingrained cultural notions of the differences between male and female brains, notions that have been used to justify the subjugation of women.

Whether the brains of men and women actually vary in form and function is a hotly debated question in psychology and neuroscience. Cultural discussion of gender and brains tends toward a reductive, binary view of neurobiology: Men are more aggressive and sex-focused, and their brains tend toward building systems; women are more emotional and communicative, and they tend toward empathy. Pop culture is rife with this men/women-are-just-soooooo-alien-how-can-I-possibly-understand-them-without-help idea. It is the basis for many stale stand-up routines and films, of course, and for a litany of books about relationships. John Gray’s 1992 Men Are from Mars, Women Are from Venus is perhaps the best-known example and is now fully embedded in the cultural lexicon (thoroughly unpacking the problems with this book and its legacy is a heroic endeavor that I don’t have room for here).

But a quick search reveals a glut of more recent examples of (super heterocentric) relationship advice books that draw on the same kinds of ideas, including Gregg Michaelsen’s To Date a Man, You Must Understand a Man, which features a cover illustration of a person in profile with a maze where their brain would be, Understanding Men: Know How Men Really Think by James Kingsley and Stefanie Maria Rhoden, and, my personal favorites—and yes, these are real—the books by husband and wife team Barbara and Allan Pease: Why Men Don’t Listen and Women Can’t Read Maps, Why Men Don’t Have a Clue and Women Always Need More Shoes!, and Why Men Want Sex and Women Need Love (groan, double groan, triple groan). All of these books rely on a foundation of biological essentialism—the idea that men and women are fundamentally different because of innate, immutable qualities, including the anatomy of their brains. These ideas spill over into many aspects of our lives—remember when the former president of Harvard University said science and math fields are male-dominated in part because of genetic differences between men and women?

If your feminist alarm bells are ringing, that’s good. The science of whether sex determines anything about brain structure and function is actually far more complicated than the simplistic view put forth by, say, Louann Brizendine, author of the books The Female Brain (2006) and The Male Brain (2010), both of which were packed with messy, often unsupported assertions and inferences. As Harvard molecular and cellular biology professor Catherine Dulac explained to Scientific American last year, “[I]t is assumed that the male and the female brains are very different because male and female behaviors differ so significantly. But over the last few decades, neuroscientists have been looking for major anatomical differences and did not find that many.”

A buzzed-about recent study, titled “Sex Beyond the Genitalia: The Human Brain Mosaic,” helps debunk the notion that there are distinct male and female brains. The 2015 study shows that brains cannot be categorized as male or female based on their structure. Instead, we should see brains as a big, heterogeneous group, and each brain as a “mosaic” that may have any combination of characteristics. Our brains are one more place where gender is best seen as a spectrum—not a cut-and-dry binary. “[M]ost brains are comprised of unique ‘mosaics’ of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males,” notes the study’s designer Daphna Joel, a professor in the school of Psychological Sciences at Tel-Aviv University.

Undermining the commonly held belief that males and females have different brains is important because sex differences between brains has been used as a justification for social differences and inequalities. There’s a long tradition of biological research being used to justify racism, sexism, ethnocentrism, and a very long list of other forms of oppressive social organization. When biology and social differences are linked, those social differences are often thought to be biologically determined. For instance, the 18th-century practice of phrenology used measurements and classification of human skulls to “prove” the superiority of Caucasians. Later, the fact that women tend to have smaller brains than men would be used as a reason to prevent them from attending college and arguing (as late as 2006!) that women are just not as smart as men because we have smaller brains. Biological determinism is a slippery slope that starts with observations of differences between people and slides into a belief that the ways society is structured around those differences are normal, natural, and inevitable. It also tends to lead to a fatalistic view: This is just the way things are.

The mosaic-brain theory pushes against these ideas. It says that there are differences between brain structures, sure, but it would be more accurate and useful to think of all brains as part of one group that displays a wide variety of anatomical characteristics. The conclusion often drawn from previous neuroscientific research was that differences between groups of male and female brains were greater than differences within those groups. The mosaic brain study argues that all human brains exist on a spectrum and even suggests that sex should not be used as a variable in scientific studies of the brain because “comparing brains of females to brains of males would be analogous to comparing two samples randomly drawn from a single population of brains.”

Of course, not everyone agrees with this conclusion. Other researchers and folks in the field published responses to the study that challenged its methods, premises, and conclusions. One common critique was that the study focused on brain anatomy rather than brain function and therefore could not detect sex-based differences in how brains actually work. Another critic was troubled by the idea that in order for a brain to be classified as “male” or “female” according to Joel et al.’s definition, it would have to be entirely so and could not display any characteristics of the other classification, which the critic thought unreasonable.

As a response to these critiques, Joel published a follow-up opinion piece coauthored with Anne Fausto-Sterling, a biologist and professor in the Department of Molecular Biology, Cell Biology, and Biochemistry at Brown University who is known for her work challenging binary understandings of biological sex. Joel and Fausto-Sterling clarify the goals and outcomes of the research: They are not denying that differences between brains exist, they are just challenging the accuracy and utility of funneling those differences into two sex-based categories.

This study, unsurprisingly, in a culture that is deeply invested in binaristic views of sex and gender, is not without its detractors, and some of them seem to raise valid critiques of the science. Ultimately, though, the study seems like a step in a good direction. Research that flies in the face of biological determinism and moves toward dismantling the sex and gender binaries can only be a good thing, even when it’s flawed.