As the tech industrys well-documented gender disparity once again enters the spotlight, even Michelle Obama is calling for men to make room at the table for women and other underrepresented groups.

While some people attribute the lack of women in tech to a host of issues (from social biases in childhood education that discourage women from analytic fields to a culture that silently condones sexual harassment in the workplace), others believe the answer is a little more...primal. Maybe mens brains are genetically more adept at logical reasoning. I read a study that showed that boys are better at mentally rotating cubes when theyre younger.

And there are indeed quite a lot of studies that show that men and boys are better at mentally rotating cubes, that boy babies prefer mobile toys to dolls, and other experiments that hint at a genetically predetermined male advantage in STEM.

There is also little question that currently, more men are involved in STEM fields, and that mens and womens brains are different. So its easy for people to put two and two together and assume that these differences are hardwired. That the reason that there are so few women in tech is *neuroscience*.

Thankfully, there is also Cordelia Fine. In her book Delusions of Gender, Fine dissects the various neuroscientific theories behind an intrinsic male superiority in STEM abilities and the landmark studies that supported them. A neuroscientist and researcher by trade, Cordelia Fine examines how social ideas about gender have influenced the hypotheses and methods used to study gender in as it relates to the brain. She then points out major logical faults.

Delusions of Gender illustrates how gender bias leads researchers to make flawed neuroscience conclusions that then reinforce gender bias. Ive created a brief timeline to offer a taste of how this dynamic has played out over the last 130 years:

Fines response: Did he really know not a single weedy intellectual, nor one muscular chump, to provoke him to wonder whether physical strength really was correlated with tenacity of brain action? We now have evidence to show that neither sheer brain size nor brain-to-body mass ratio are predictive of intelligence. In short, those missing five ounces mean nothing.

Again, here is a neuroscientist merely listing the observed differences between adult male and female brains. Dana does not offer a reason why these differences would lead to the conclusions he draws. The power of shared preconceptions was so overwhelming that nobody questioned the lack of real scientific evidence. Instead, scientists and readers alike accepted that if X (the observed physical differences between male and females) is true, and they believed Y (the superiority of male intellect) to be true as well, then X must cause Y.

In additional to this logical fallacy, Fine points out that observed physiological differences between male and female brains do not necessarily result in differences in brain function: some differences offset each other, and others are different means to the same behavior end.

Modern ideas of men as rational/unemotional and women intuitive/irrational seem to arise from a theory by Norman Geschwind and his colleagues in the 1980s.

In 1982, Geschwind and Behan published a short paper proposing a complicated theory behind brain lateralization. The implications for gender went something like this: during development, male fetuses experience a surge of testosterone. Geschwind suggests that this surge slows the boys left hemisphere growth, leaving male babies with greater potential for superior right hemisphere talents, such as artistic, musical, or mathematical talent.

This theory spurred decades of research into fetal testosterone, leading scientists to draw conclusions between factors like digit ratios and math abilities (again--for a more detailed dive into individual studies, read the book!).

Meanwhile, it is widely ignored that neurophysiologist Ruth Bleier points out that a premise of the fetal testosterone hypothesis, that fetal testosterone leaves boy babies with cramped left hemispheres, is inconsistent with post-mortem studies of fetal brains. So if male fetuses do not actually have smaller left hemispheres (and for that matter, expanded right hemispheres), there is no reason to believe that fetal testosterone grants them superior right hemisphere talents.

The Fetal Testosterone Hypothesis hasnt gone away, but a new generation of researchers has put forth a new theory of genetically determined male dominance in STEM abilities: The Spotlight/Floodlight hypothesis, as coined by Ruben Gur in 2005. The general idea is that women, as observed by Ruben and his wife Raquel Gur, have larger corpus callosum, the area that connects the two brain hemispheres. They pinpoint the splenium, to be specific. Because of this enlarged splenium, women have greater inter-hemispheric traffic, leading to a floodlight mind better for multitasking, whereas men, they posit, have less inter-hemispheric traffic, creating a spotlight mind better for focusing, specifically on visuo-spatial tasks deemed essential for developing STEM skills.

Hmm...women are better at multi-tasking? At first, this hypothesis seems to empower women! But then, as Fine notes, we realize that this is just new marketing copy for an idea that continues to justify the segregation of women from math and science.

But by creating and emphasizing any distinction between the functions of mens and womens brains, we open ourselves to a world in which neuroscientists can say that one genders brain is better for something than the brains of others. It was creativity in the Victorian age, judicial thought at the turn of the 20th century, and it is STEM abilities now.

Simon Baron-Cohen, a longtime champion of gender-based neural differences, demonstrates how this unintentionally sexist dynamic plays out. Baron-Cohen quoted the Spotlight/Floodlight hypothesis in Science, noting that the increased local connectivity of male brains makes them better for understanding and building systems, whereas womens long range brains make them better for empathizing.

Unfortunately for Baron-Cohen and the Gurs, meta-analyses conducted in 2004 and 2008 have showed that there is little evidence to support the idea that a female brain has on average a larger splenium. Studies that conclude this tend to suffer from small sample sizes.

A small sample size alone is not the problem. A study can have a small sample size and be perfectly valid. The problem is that studies that show difference are more likely to be published. So if 20 studies are conducted and only one shows a difference, that one will be published because it causes a stir. But by looking at all twenty studies in a meta analysis, we see that the one published study was only significant because of its small sample size.

So lets recap: the Spotlight/Floodlight hypothesis posits that 1) because women have a larger splenium (part of the corpus callosum, which connects the two hemispheres), the hemispheres in womens brains do more talking; 2) men have less hemispheric talking because of a smaller splenium; and 3) less hemispheric talking is better for building systems e.g. engineering abilities, therefore men are better at engineering. Even disregarding the dubious nature of claim #3, meta analyses show that women do not on average have a larger splenium, which eliminates this entire hypothesis as a possible neuroscientific explanation for the abundance of Y chromosomes in tech startups.

In addition to the lack of evidence to support the hypothesis that a woman has a larger splenium, the Gurs themselves found evidence that contradicted the Spotlight/Floodlight hypothesis. The Gurs and their colleagues found that in some parts of the brain, men show more bilateral (cross-hemispheric) activation than women on certain visuo-spatial tasks. As a result, they edited the Spotlight/Floodlight hypothesis to the following: optimal performance on these STEM-skill-determining visuo-spatial tasks now requires unilateral activation in primary regions AND bilateral activation in associated regions.

At this, Cordelia Fine delivers one of the best passages in the book:

Basically, the Gurs coined Spotlight/Floodlight when they found evidence for less bilateral activation in male brains, then claimed that less bilateral action = STEM brain. Then they found more bilateral activation in male brains for other STEM tasks, which prompted them to change their hypothesis. The Gurs reformulation now claims that an optimal STEM brain has unilateral (spotlight) activation and some bilateral (floodlight) activation.

Cordelia Fine pokes fun at their shifting stance while suggesting again that certain scientists are so determined to find evidence for male STEM superiority in the brain that they will label anything they find as the cause.

Fine is not saying that its impossible that there is something inherent in males that could make them more suited for math and science. She simply argues that the current support for this idea is poorly substantiated.

To reiterate: the debate in question is not about whether there are differences between men and women. At every level of behavioral science, from the brain to behavior, differences are well-documented. The debate is over whether or not these differences are predetermined by genetics, or if they are the result of brain plasticity and stereotype threat in a society where, from infancy, we see messages that men=mars=science and women=venus=empathy.

In the end, Delusions of Gender has two calls to action: 1) Scientists should have more rigor when conducting and reporting on studies that have implications as serious as the origins of gender differences. 2) Readers should be vigilant when presented with such studies and not be dazzled by the use of neuroscience simply because it is neuroscience.

For anyone who is interested in the brain, research methods, applied science, gender, parenting, the workplace, human nature, or general sass, this book is an absolute must read.

Cyndi Chen writes about jobs, women, and technology. She is currently pursuing her MBA at Yale University. Interests include human narratives, the brain, pop culture, art, the Bachelor, and railing against the wedding industry. Follow Cyndi on Twitter at https://twitter.com/cyndithinks

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Summer Reading: how biases influence neuroscience research on gender - HuffPost