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Professor of Medicine challenges what we know about sex, gender, and the human brain

Marcia Stefanick

Nov 5 2020

“Why do we still have battles about whether sex differences in the human brain exist because of biology or sociocultural factors - nature versus nurture? Why don’t we acknowledge that culture and experience change how each unique brain develops from conception through our lives?” Marcia L. Stefanick, professor of medicine, posed these questions during a recent talk for the Clayman Institute Faculty Research Fellows program titled “Biological and Neurophysiological Basis for Gender Identity and Sexual Orientation.” Stefanick questions how binary thinking on gender and sex, and sexual orientation, has led to conclusions in the various disciplines of neuroscience that men and women start out with different brains, and that these different brains lead to different behaviors, cognitive skills, and emotional reactions. Furthermore, this literature tends to attribute and emphasize a biological or genetic explanation to these presumed differences, ignoring or downplaying social and cultural factors like family socialization. Instead, Stefanick proposes an approach that challenges the gender/sex binary that considers how our cultural upbringing leads us to think about sex, gender, and ourselves.

Stefanick contends that gendered stereotypes contribute to how the public and neuroscientists conceptualize and talk about the brain and human behavior. Anatomical differences in the sizes of the brains of men and women, and different areas of the brain linked to specific functions are often presented as evidence of inherent (binary) sex differences in the human brain and often assumed to explain cultural stereotypes of men as more aggressive and with higher sex drive than women; furthermore, many still believe men evolved as hunters in prehistoric societies, whereas women’s important reproductive roles led them to demonstrate more emotion and develop better communication skills than men, and become the gatherers. Stefanick debunks this perspective, citing research that shows that differences in overall body mass explain differences in the sizes of men and women’s brains. Furthermore, structural differences do not entail functional differences because human brains, regardless of gender, have the same basic wiring; however, neuroplasticity, i.e. how the brain develops, is strongly influenced by experience and education. 

Despite the persistence of arguments that reinforce a sex and gender binary, more recent research and evidence paints a more complicated picture of how the human brain shapes sexuality and gender.

Despite the persistence of arguments that reinforce a sex and gender binary, more recent research and evidence paints a more complicated picture of how the human brain shapes sexuality and gender. For example, Stefanick references her own research that examined how the introduction of sex hormones to newborn male and female rats altered their mounting behavior. Castrated males treated with estrogen were highly receptive to being mounted while female rats treated with testosterone engage in male mounting behavior. Stefanick strongly cautions, however, that human sexuality and reproductive behavior are not one and the same. For example, female rats are not at all receptive to being mounted unless they are ovulating or treated with estrogen; whereas, human females may be interested in sex throughout their menstrual cycle and after menopause. 

 Scholars today agree that while sex matters, even at the cellular level, what we refer to as sex differs from what we consider gender. Still, disagreement arises about how and why these perceived differences exist. Stefanick states, “People [scholars] love the idea of sex differences…[but] we have to challenge this! We have to look at how gender interacts with the brain.” Scholars who take gender into account point to how gender and sexuality has existed as a spectrum rather than a binary on every continent throughout human history. During the talk, Stefanick provided examples of several cultures throughout the world that recognize a third (or more) gender(s) or sex category. For instance, while Hawaiian and Tahitian societies recognize a third gender referred to as Māhū, intersex people known as Güevedoce have been identified in the Dominican Republic and Papua New Guinea. This diversity of terminology prompts Stefanick to point out how these terms complicate how we conceptualize biology in terms of gender and sex. Stefanick suggests we embrace a gender/sex continuum rather than binary categories.

A gender lens
exposes gaps in knowledge,
identifies root causes of barriers,
and proposes workable solutions.