Before babies learn language, they can perceive gender stereotypes. Studies suggest that at 18 months, before they even have the ability to understand their own gender identity, infants will focus longer on images that challenge typical roles - a man putting on lipstick, for example. By age two, they can locate themselves in the gender system and identify pictures of males and females based on external characteristics like hair length and clothing. But they cannot discern a naked person's sex.
These phenomena are examples of ways our social context influences our development, said Anne Fausto-Sterling, professor of biology and gender studies, in a public conversation Friday with Debbie Weinstein '93, assistant director of the Pembroke Center for Teaching and Research on Women. Students and their parents filled Pembroke Center 305 to listen to the talk, entitled "An Alternative to Nature v. Nurture: Biology in a Social World."
"These days the nature-nurture debate is a fallback for a lot of people," Fausto-Sterling said. "But actually the whole contour of that so-called debate is really changing. It's changing across the board because people are becoming much more aware of the ways in which nature and nurture are integrated phenomena."
She explained a study of London taxi cab drivers that illustrates the profound impact society has on biology. To become certified, cab drivers must memorize more than 20,000 roads and key sites in London. Scientists found that such training causes a key memory structure in the brain, the hippocampus, to grow. "Training to fill a very particular cultural niche results in their physical biology changing," Fausto-Sterling said.
The study's results counter many people's belief in "nature" as permanently fixed and unchangeable. People are also prone to believe in "nurture" as "infinitely pliable," but certain cultural phenomena are "extremely difficult to change," Fausto-Sterling said.
Over time, she and other scientists have realized that even subtle social differences can shape development. While early feminist psychologists focused on whether children were punished or rewarded for behaving in certain ways, "daily experience starts from the moment of birth on," she said.
To examine some of these early influences, Fausto-Sterling teamed up with Cynthia Garcia Coll, professor of education, psychology and pediatrics, to study how mothers interacted with infants. They are in the process of observing, coding and analyzing weekly videotapes of interactions. Though they have not finished their analysis, Fausto-Sterling said they have found differences between how mothers interact with girls and boys. Mothers speak more to girls but will move boys around to encourage them to walk and crawl, she said.
Fausto-Sterling said she uses the dynamic systems theory to approach much of her work. This approach relies on multiple levels of organization that influence each other dynamically. For example, a baby's motor cortex, muscle development and weight all influence his ability to learn to crawl. If one level destabilizes, the whole system turns to chaos but will then find a way to stabilize again, Fausto-Sterling said.
The multiple layers that influence development may change the way we approach cultural issues like transgender identity, Fausto-Sterling said in response to a question from Weinstein about the stakes of her research. Currently, people who identify as transgender often change their bodies surgically, through a "medically complex and dangerous set of procedures," Fausto-Sterling said. But changing the social structure of society to be more accepting of people whose gender identity and biological sex do not match is an alternative worth considering, she said.
In the long term, there "has to be a better way to train scientists to think in more social contexts," Fausto-Sterling said.
Emma Bratton '14 said she was particularly struck by the fact that 18-month-olds are able to recognize when gender stereotypes are violated. "Gender norms are really limiting, and so the fact that something is learned so early that is so limiting to gender identity in general is troubling to me."