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Is the female brain innately inferior?
Stanford neuroscientist tackles myths about the brain
We have all heard that women are from Venus and men from Mars, with brains from equally distant galaxies. You may have heard that in comparison to men, women have smaller, inferior brains ruled by estrogen instead of testosterone, and that they are innately less mathematical. Some believe that these differences cause men to have fundamentally superior brains, leading to disparate careers, achievements and successes. With women holding just 16 of the CEO spots at Fortune 500 companies, winning only 17% of the seats in Congress, and graduating with just 18% of all computer science degrees, innate brain differences have even been used to explain, or justify, these outcomes.
Josef Parvizi, Clayman Institute fellow and assistant professor of Neurology and Neurological Sciences at Stanford University Medical Center, argued such statements are beliefs unsubstantiated by neuroscience, or even by basic logic. In a talk given at the Clayman Institute, Parvizi challenged these myths.
Gender Brain Myth #1: Brain size matters
The first myth Parvizi tackled was that women are innately less intelligent than men because they have smaller brains. While men have larger brains on an absolute level, there are no sex differences in brain size once body mass is controlled. The male brain is not proportionately larger than that of the female brain; men are just physically larger, on average. Furthermore, if absolute brain size were all that mattered, whales and elephants, both of which have much larger brains than humans, would outwit men and women.
Gender Brain Myth #2: Women and men have different brains due to estrogen and testosterone
Many believe that “male” and “female” hormones differentially shape the brain, leading some to conclude that these hormonal differences cause men to be better leaders and thinkers. Although it is true that males generally have more testosterone, while females have more estrogen, men and women possess both hormones. These hormones perform other functions besides those related to reproduction; for instance, the male brain needs estrogen for normal brain development and function. And testosterone is also important to women; for example, in the development and maintenance of libido.
Although the popular press often touts the importance of testosterone to the behavior of men, this claim is also overstated. A 1996 study showed that even unnaturally large doses of testosterone did not alter the mood or behavior of normal men (although it did exaggerate aggression for men who were already aggressive).
Lastly, Parvizi stated that even if estrogen and testosterone did shape the brain in different ways, it is an unsubstantiated, logical leap to conclude that such differences cause, “…men to occupy top academic positions in the sciences and engineering or top positions of political or social power, while women are hopelessly ill-equipped for such offices.”
Gender Brain Myth #3: Men are naturally better at math
But perhaps the most damning myth, which has even been espoused by a former president of Harvard, is that men are innately better at math and women are naturally better at verbal tasks. The logic is that gendered differences in math and verbal scores on standardized tests must result from intrinsic, biological differences in the brains of women and men. According to Parvizi, this logic is flawed: “Differences seen in cognitive tests do not necessarily provide direct evidence that those differences are in fact innate.”
If not inherent abilities, what can explain the differences in test scores? Evidence shows that test scores are not immune to social factors. Extensive empirical research on stereotype threat has demonstrated that if a person is exposed to a negative stereotype about a group to which they belong (e.g. women, Asians, African-Americans), they will then perform worse on tasks related to the stereotype. A striking example comes from a study on Asian-American women. When reminded of being Asian (which invokes stereotypes of high math ability) they scored higher than the control group (which was not reminded of their race or gender) on a math test. However, when Asian-American women were reminded of being female (which invokes stereotypes of poor math performance), they scored lower on the math test than the control group.
In this manner, social factors can greatly influence test performance. “Consequently, we are not in a position to draw any conclusions regarding sex differences in the brain and their relationship to differential cognitive abilities,” concluded Parvizi, “as we have yet to establish beyond a reasonable doubt that there are indeed real differences in ability.”
Neuroscience to the rescue: The difference between being & becoming
So if women and men do not have such innately dissimilar brains, why do they seem so different? Parvizi explained that the brain exhibits significant neuroplasticity, as it able to make structural and functional changes in response to environmental inputs; in his words, “the brain is molded by experience.” As the brain replicates the same signals over time, the networks through which they are sent become progressively stronger, as repetition reinforces both the networks and brain synapses. Building off, “…what we know about the neural basis of learning, one can argue that the map of associations in the brain is sculpted by our experience throughout our life. Even if the hard wiring of the brain remains unchanged, the function of the hardware is constantly altered by experience.”
Thus, “if we are to entertain the idea that humans ‘experience’ life differently, and that different experiences mold the brain function differently, then we must also seriously consider that gender (along with class, ethnicity, age, and many other factors) would also contribute to this experience, and that they will contribute to molding of the brain.” For instance, it is a commonly known fact that the blind develop superior hearing, in order to compensate for the lack of visual stimuli. Due to the brain’s ability to adapt, this difference becomes a part of the brain structure (especially for those who are born blind); neuroimaging has found that many blind individuals use parts of their visual cortex to process sound.
So if women and men have systematically different life experiences and face dissimilar expectations from birth, then we would expect that their brains would become different (even if they are not innately dissimilar), through these different life experiences. Even if neuroscientists see differences in the brains of grown men and women, it does not follow that these differences are innate and unchangeable. For instance, if girls are expected to be more adept at language, and are placed in more situations that require communication with others, it follows that the networks of the brain associated with language could become more efficient in women. Conversely, if boys receive more toy trucks and Lego’s, are given greater encouragement in math and engineering classes, and eventually take more STEM (science, technology, engineering and math) courses, it follows that the sections of the brain associated with mathematics could become more efficient in men.
However, as Parvizi noted, “The tricky part is that we do not make the mistake of taking account of these differences as evidence for biological determinism.”
Josef Parvizi is an Assistant Professor of Neurology and Neurological Sciences at Stanford University Medical Center, and was a Faculty Research Fellow at the Clayman Institute during the 2010-11 academic year. He specializes in the field of clinical neurology and cognitive neuroscience and uses a combination of functional imaging and intracranial electrophysiological recordings and electrical stimulation within the human brain to study cognition and emotion and how they are altered by neuropathological problems. The general theme of his research is the relationship between brain anatomy, physiology, and human cognition.