Daphna Joel was already an established neuroscientist in 2009, when she chose to launch a gender studies course at Tel Aviv University. While preparing the class curriculum, she became deeply interested in the mechanisms through which gender is formed. Her research led her to an experiment by a professor at the University of Maryland that demonstrated how characteristics of certain neurons in animal brains could change from male to female, or vice versa, when exposed to a stressor for 15 minutes.
“I realized that if certain areas of the brain could change from the typical ‘female form’ to the typical ‘male form’ under stress, there was no point in talking about the female brain and the male brain,” Joel told Haaretz (paywall).
Around the same time, Cordelia Fine was prompted to write Delusions of Gender: How our minds, society, and neurosexism create differences, which would become a zeitgeist-y hit,after spotting the book Why Gender Matters, by the American psychologist Leonard Sax, at her son’s kindergarten in Australia. Sax’s guide, she says, presents as fact the idea that “hardwired sex differences in the brain mean that girls and boys should be parented and educated differently.” Fine had studied brain structure during her PhD work at Institute of Cognitive Neuroscience at University College London, so she looked into the studies Sax cited. She was “shocked at the disconnection between what the studies revealed, and the practical implications being drawn from them.”
We take for granted how often laymen and even researchers use science—and specifically neuroscience—to “verify” stereotypes about gender: That men are naturally more competitive, for instance, or that women are more in touch with their emotions and better skilled at communicating. Such notions aren’t just academic, but pervasive and potent, indirectly influencing the way we organize our households and organizations, not to mention the way we see our relationships, and even ourselves.
Recently, former Google engineer James Damore was fired from the company after writing a memo criticizing its diversity programs, and suggesting there may be biological reasons that women aren’t fully represented in engineering. Studies have found that women care more about people than things, wrote Damore, who holds a graduate degree in biology and cited studies from both Wikipedia and reputable institutions.
“When I hear stories like the Google memo in the news, I think, Is this 1873 or 2017?” says Kimberly Hamlin, a professor of American Studies at Miami University. Hamlin, who is the author ofF says the same arguments about women’s abilities keep being repackaged with new natural reasoning because “naturalist” explanations for why there are few women in science and tech are easier to accept than the more complex structural ones.
But some scientists believe it’s time to question the pat explanation evolutionary biology offers about sex and gender: Namely, that gender is entirely pre-programmed in utero.
Evolutionary biologists are behind many popular theories that have gained traction outside academia, like the notion that our brains are “hardwired” with the skills our Stone Age ancestors needed to hunt and kill (if we are men), or keep children safe while also preparing food (if we are women).
Within neuroscience, however, a loose, global network of five female scientists are at the forefront of a movement to liberate people of all genders from what they see as the sexist limits of “hardwiring.” The question is whether their scientist peers will take them seriously.
The gendered brain
Cordelia Fine, a psychologist, writer, and professor at University of Melbourne, initially met Rebecca Jordan-Young, an interdisciplinary scientist who chairs the Women’s, Gender, and Sexuality Studies department at Barnard College in New York in 2010, at the inaugural NeuroGenderings conference. The two discovered, to their mild horror, that they both had books in press on the same topic. Fine’s Delusions of Gender was shortlisted for several book awards and named a 2010 book of the year by The Guardian and the Washington Post, and Jordan-Young’s Brainstorm: The Flaws in the Science of Sex Differences, was called “by turns fascinating and appalling” by the Los Angeles Times.
NeuroGenderings had been co-organized by Anelis Kaiser, a Swiss neuroscientist and professor of gender studies in STEM at the University of Freiburg, in Germany. At the second conference, in Vienna two years later, she helped connect Daphna Joel, a professor of psychology and neuroscience at Tel Aviv University in Israel, and Gina Rippon, a professor of cognitive neuroimaging at Aston University in the United Kingdom, to Fine and Jordan-Young.
Today, these five researchers, while still working independently, also join forces in pairs or as a group to write papers for the scientific and popular press, and to respond to public issues about gender and neuroscience, explaining the many ways that neuroscience studies and their tantalizing headlines are misleading or misinterpreted.
When Damore’s Google memo took over the news cycle, for instance, the scientists were contacted by reporters from around the world. In Joel’s notes for Spanish reporters, which she shared with Quartz, she wrote: “Studies do often find differences between women and men in specific cognitive tasks, personality characteristics, interests and attitudes. However many of these differences are very small; and some of the differences are different in different societies (for example, in some countries boys do better on average in math, whereas in others girls do better.)”
What’s more, many gender gaps can be eliminated with training, she added, a point which Rippon also made to the Guardian. With some practice playing the right sort of video game, women can boost their spatial reasoning skills to match those of boys.
Rippon and others have called also attention to brain plasticity, which complicates evidence from brain imaging tests since men and women are both saddled with gender expectations from the time of infancy, and develop skills and behavioral tendencies accordingly. These learned behaviors could be responsible for literally changing the shape of certain structures in one’s brain, in the same way that memorizing London’s streets alters the physical structure of cabbies’ hippocampus, the area of the brain associated with memory.
Perhaps most importantly, studies have also shown that gender biases exist within science, and a researcher’s implicit assumptions can inform the methods and language they use to build a study. Damore’s assertion in his memo that “women on average show a higher interest in people and men in things” is a timely example of how this happens, Fine writes to Quartz. She explains that meta-analyses of career interest surveys have shown that 80% of men are more interested in “things,” compared to the average woman. But some psychologists who have studied such surveys find them problematic because the “things” they include are often associated with men—the surveys do not try to gauge a subject’s interest in, say, taking apart and reassembling a dress.
Such concerns make it obvious that culture and biology cannot be disentangled, according to Daphna Joel. In studies that find differences between genders, “there is no way to prove that these differences have an innate basis, because the studies are conducted in adults, who have lived their entire life in a highly gendered society.”
The Mosaic brain model
Ask Joel what the most persistent myth is about men’s and women’s brains and she says, “that they exist.” And it’s a problem that has “a very important role in maintaining our social structure.”
The myth endures, Joel proposes, because we assume that since humans have two separate reproductive systems (with very few exceptions), and because sex hormones also play a role in brain development (in both those sexes), we must have two separate brains.
“What my work has shown, first on the basis on data from animals, and then in the human brain, is that the next step is unjustified,” Joel says. “It’s not a logical conclusion and it’s not the only possibility.”
Where there are plenty of studies that show sex hormones affect the brain, and that there are some group-level differences between male and female brains—for example, on average, women have more gray matter then men—what’s not proven, according to Joel, “is that these effects add up to create two types of brains: male and female.”
That was the paramount finding of her recent paper, “Sex beyond the genitalia: The human brain mosaic,” which she wrote with a team of neuroscientists and published in 2015. In the meta-analysis, the scientists compared the brains of 1,400 men and women, analyzing the volume, connections, and other physical characteristics of brain structures. Though there were some extreme differences in outliers of both sexes, they found that, on an individual level, brains contained a mosaic of bothsex-congruent and sex-incongruent features. For example, the left hippocampus, which is associated with memory, was more often bigger in male brains, but a woman with a large left hippocampus was common.Depending on the sample, 23% to 53% of individual brains contained a mix of “typically male” and “typically female” traits, while only zero to 8% of the subjects were found to have “all-male” or “all-female” brains.
The same was true of gender as it relates to personality traits and interests—such as scrapbooking or playing video games—which Joel also examined in a meta-analysis of three data sets for the same study. “The only thing you can say is that more women have more feminine than masculine characteristics, and more men have male characteristics on average than women,” says Joel. To her, however, “it really doesn’t matter how many you have of these characteristics. The question is, who are you?”
In the Guardian, Joel and Fine summed up the metaphysical questions posed by the mosaic brain model poetically:
Which of the many mosaics that males display should be considered the male nature? Is it a profile of pure masculinity that appears to barely exist in reality?
Or is it time to let go of binary thinking and celebrate the fact that there are many different ways to be male, to be female, to be human?
A common critique: This is political
While the scientists have found support from within the scientific community, and they are not alone in their conclusions, they are also often dismissed by evolutionary biologists who believe that gender is innate, and their supporters. Jordan-Young, recalls facing “purple faced” academics at one conference where, as the keynote speaker, she presented her findings from Brainstorm.
For that book, Jordan-Young, who has a special interest in research methodology, had painstakingly analyzed hundreds of studies around the “brain organizational paradigm,” which, as she explains to Quartz, proposes “that the brain is essentially organized to be either more masculine or feminine by the degree of testosterone exposure in utero.” In her examination of the studies, however, she found that this thesis was not supported by any cohesive body of research.
One common complaint among their scientist critics is that their work is driven by ideology, and that the women are using arguments about neuroscience to undo gender inequities. “The Science of the neurobiological basis of behavioral sex differences is Objective,” Fine jokes, “while any critiques of that science is Ideological.”
This attitude “isn’t just a very naïve view of science,” she adds, “it’s also highly counterproductive to scientific progress.”
Working in Europe, Kaiser says her motives within the lab are also questioned, a consequence of being open about her feminist values. “We are ‘the others,'” she tells Quartz.
“When you are working within normative ideas, you do not need to use any labels,” she says, which creates the illusion for those scientists they are working without an underlying belief system. “I try to make this point when I’m asked if I’m an ideologist or not: maybe we are, but then all of us are.”
Joel says her first paper on the brain mosaic was rejected from the leading journals: Editors told her the topic wasn’t of general interest. After a year of rejections, she sent it to an open-access journal. Her second paper, published in PNAS, was received with enthusiasm from the media and public, receiving coverage all over the world, but was harshly criticized in ways she says she found sexist within some professional networks.
The scientists’ most vocal opponent may be Larry Cahill, a professor of neurobiology at University of California, Irvine, who wrote about the women’s research in “Equal ≠ The Same: Sex Differences in the Human Brain,” an essay published by the Dana Foundation, a private philanthropic organization that funds brain research, in 2014. He called scientists like Joel, Rippon, Fine, Jordan-Young, and Kaiser, “anti-sex differences,” and expressed concern that they were afraid to find a distinction between male and female brains because it would somehow mean that men and women were not equal.
By contrast, he tells Quartz, his work for the last 17 years has been focused on defining sex differences in the brain —which he says exist on every level and vary in size— because neuroscience had been treating male and female brains as if they were the same. He says this view puts women at risk for diseases, such as Alzheimer’s, that manifest differently in men and women.
Cahill also asserts that, yes, the brain is plastic, but only within certain limitations, and that the reason Joel’s study did not find two categorical genders was because her definition of “internal consistency” was extreme, an assertion that was also made by a different group of researchers in a study described in a letter to PNAS. “It’s a joke,” he says. “I wish people would read the two papers and come to their own conclusions.”
Joel, for her part, responded to the team of researchers who challenged her definition of internal consistency. She says their data actually validated her findings, but were presented in a way that “attests more to their political agenda than to their wish to advance science.”
And together, the five women have written a detailed response to Cahill’s critiques, clarifying that they “are neither ‘for’ nor ‘against’ sex differences (or sex similarities, for that matter)” and proposing that “focusing only on similarities or differences is misleading.”
They emphasized the points on which they agreed with Cahill, particularly in terms of sex and brain development, but urged that “we need to develop a new framework for thinking of the relation between sex, brain, and gender that better fits current knowledge, and that takes into account distributions, changes, overlap, variance, and most of all, context.”
The irrelevant, gendered brain
Neuroscientists are beginning to integrate ideas about culture into their research, according to Fine, who says she’s feeling positive about the direction science is going.
In her new book about women in science, British journalist Angela Saini speaks to Paul Matthews, a neuroscientist at Imperial College London who agrees with Joel and others, saying, “There’s a lot of variability in individual brains. In fact, the anatomical variability is much greater than we ever realized before. So the notion that all people of the male sex have a brain that has fixed characteristics that are invariant seems less likely to me. In fact, so much less likely that I think the notion of trying to characterize parts of the brain as more male-like or more female-like actually isn’t useful.”
Regarding the question of whether certain traits that we call “male” or “female” (at least in the West) are determined by biology or socialization, Joel says she isn’t sure why scientists or the public are so captivated by it. “The question doesn’t interest me, because we can’t answer it,” she says.
It’s also irrelevant in terms of the way society should operate, she says. For example, if a child can’t read, we give them extra lessons and find ways to help them improve. “We don’t say, it’s biologic so it must be natural and good for the child,” says Joel. “Likewise, we don’t celebrate aggression just because it is natural.”
“If we feel empathy is a great characteristic and someone is not empathetic by nature, we help them to enhance their empathetic abilities. It’s not, ‘She is not empathetic, so let’s help her,’ but ‘He is not empathetic, but it’s fine, he’s a boy,'” she says. “What society needs to decide is what virtues or characteristics we would like to encourage.”
As for the arc of research, Hamlin says that historically, it has mostly taken women scientists mounting careful and convincing studies to slowly dismantle baseless, damaging ideas about gender stereotyping that science is not immune to, despite the field’s objective aims. These researchers believe that, in the end, the power of science will uncover the truth—if other scientists will only allow it.
Correction: This article has been updated to reflect that it was Joel’s first paper, published in 2011, that was initially rejected by editors and eventually published in an open-source journal. Her second paper on the same topic was published in PNAS and was well-received. Additionally, Larry Cahill’s article published in DANA was not a response to Joel’s 2015 PNAS paper, but a response to the research generally, as it was published in 2014.
Chapter 16 of my book, 50 Human Brain Ideas You Really Need to Know. Here's the introduction to the book, the chapter about topographic mapping, the chapter about mirror neurons, and my post about the most important idea in neuroscience.
Summary: Subtle observable differences exist between male and female brains, but how exactly these relate to differences in behaviour is unknown. Such gender variations in the brain are often exaggerated and misappropriated, not only by the mass media but also by scientists, to reinforce stereotypes and perpetuate myths.
The science of sex differences has always been – and still is – fraught with controversy. Some believe that behavioural differences between men and women are mostly due to cultural influences, while others argue that sex differences are largely determined by biology. In reality, the situation is far more complex. It lies somewhere in the middle, and involves two related but independent factors, which are often confused or conflated.
One of these factors is biological sex, which is determined by chromosomes. Most people have either two X chromosomes, which makes them female, or one X and one Y chromosome, which makes them male. The other is gender, which is influenced largely by the socialization process. As we grow up, we learn society's norms about how males and females look and act; for most people, sex and gender are matched, and so they inadvertently conform to these norms.
Men and women's brains differ in subtle ways, and these differences are probably established in the womb, due to the effects of sex hormones, which masculinize or feminize the organ as it develops. However, we still do not understand the effects of sex hormones on the developing brain, or how the subtle differences observed between men and women's brains are related to differences in their behaviour.
Battle of the sexes?
The most obvious difference between the brains of men and women is overall size – men's brains are, on average, between 10 and 15 per cent larger than women's. In one recent study, neuroscientists compared the brains of 42 men and 58 women postmortem, and found that men's weighed an average of 1,378g (3lb), compared with 1,248g (2.75lb) for women. These size differences have been found repeatedly, but they emerge only when comparing large numbers of people, so some women's brains are larger than the average whereas some men's are smaller. These differences partly reflect the fact that men are generally bigger and taller than women, but they are not related to differences in intelligence.
Men and women's brains also differ in overall composition. Male brains tend to have a slightly higher proportion of white matter, whereas those of females have a higher proportion of grey matter in most parts of the cerebral cortex. Consequently, the cortex is slightly thicker in women's brains than in men's and, according to several studies, is slightly more convoluted as well. There are also sex differences in the size of individual brain structures. The hippocampus, a structure involved in memory formation, is on average larger in men than in women, as is the amygdala, which is also involved in memory, as well as emotions.
Another sexual variation is found in a structure called the third interstitial nucleus of the anterior hypothalamus. The function of this tiny structure is unknown, but research from four different laboratories has repeatedly found that it is almost twice as large in males than in females. It has also been linked to sexual orientation and gender identity: one study showed that it is more than twice as large in heterosexual males than in homosexual males, where it more closely resembles that of women; another found that it is smaller in male-to-female transsexuals, and larger in female-to-male transsexuals. These studies have been criticized for their small sample sizes, and the findings have not been confirmed.
Stereotypes and myths
Numerous studies show subtle differences in male and female behaviour and in cognitive functions, too. Men tend to be more aggressive and outperform women on mental tasks involving spatial skills such as mental rotation, whereas women tend to be more empathetic and perform better on verbal memory and language tasks. Findings like these are often exaggerated to reinforce the stereotypes that women are bad at reverse parking and that they love to chat!
In some cases, individual studies purporting to show sex differences in certain tasks are misappropriated. For example, according to a tiny postmortem study published in 1982, the corpus callosum, the massive bundle of nerve fibres connecting the two brain hemispheres, is proportionally larger in women than in men. This was widely reported to mean that women are better at multitasking, even though subsequent work has failed to replicate the results. A more recent study showed that women are marginally better than men at paying attention to sounds presented to both ears simultaneously – this was interpreted by some as evidence that 'men don't listen'.
Many of these claims are accompanied by the assertion that the observed differences between men and women's brains are 'hard-wired' and, therefore, irreversible. We now know, however, that brain structure and function change in response to experience, so any observed differences between the brains of men and women could also be due to differences in upbringing and socialization. To date, though, very little research has been done to investigate how different nurturing styles might influence brain development.
Box: The extreme male brain hypothesis
People with autism tend to perform poorly on tests of empathizing, or the ability to put oneself in somebody else's shoes, but do well on tests of systematizing, or finding repeating patterns. Similarly, women tend to score higher on the empathy scale, and men on the systematizing scale. These observations led one researcher to propose the highly controversial 'extreme male brain' hypothesis of autism. The hypothesis states that autism is an extreme form of the normal male cognitive profile, which occurs as a result of high testosterone levels in the womb. Accordingly, people with autism can be considered as 'hyper-systematizers' who focus more on patterns and fine details than on other people's thoughts and actions. The extreme male brain hypothesis has been used as an explanation for why autism is four times more prevalent in males than in females, and why people with autism can excel in disciplines such as maths and engineering.