Is the female brain hard-wired to be more social? A large body of research has pointed to better female performance on social information processing, but the question of whether this advantage represents a sex-based difference in brain structure has remained unanswered. A series of studies conducted by Wood, Nopoulos, and colleagues from the University of Iowa attempted to answer the question by studying sex differences in brain regions involved in social cognition.
Decades of research have shown that men tend to perform better on mathematical and visuo-spatial reasoning, while women excel on cognition tasks involving processing and interpreting social information. Even as young as a few days old, baby girls make more eye contact than boys, and by three months, show more facial expressions indicating interest, such as wider eyes and higher eyebrows.
In line with these findings, a number of studies have documented sex-related differences in brain structure, including differences in the volume of certain brain regions and different gray and white matter ratios.
But when it comes to social interactions, are male and female brains really all that different? Neuroimaging studies have identified regions involved in social cognition, in particular, the ventral frontal cortex (VFC) in the frontal lobes. The VFC is critical for normal social behaviour in humans: tasks involving facial recognition, perceiving anger in others, and experiencing moral emotions all activate this area of the brain. Patients with a damaged VFC lack inhibition and concern for others, and display impaired reasoning about others’ mental states.
In their first study, Wood and Nopoulos looked at the relative VFC volumes in adult males and females, and correlated these measurements with individual scores on an interpersonal perception task, a common test for social cognition. They found that a specific subdivision of the VFC, called the straight gyrus (SG), is about 10 per cent larger among women. What’s more, greater SG volume and surface area correlated with higher scores on the interpersonal perception task, so that individuals with better interpersonal awareness also tended to have a larger SG.
So far, so good. While their neuroimaging results were correlated with social cognition scores in males and females, the researchers decided to take their work one step further and speculate on some of the genetic factors at work during development. Since the genes located on sex chromosomes are expressed to different degrees in the male and female brain, could enhanced social cognition have a sex-based genetic difference at its root?
Wood and Nopoulos addressed this issue in a second study by testing VFC volumes in children between seven and 17 years of age. If the straight gyrus in female children and teens was larger than that of males of the same age, this would provide better evidence for an inherent genetic difference.
But the results weren’t quite what the researchers expected. Contrary to their first study, they found that SG size was actually larger in boys, while in girls, high scores of interpersonal perception correlated with a smaller SG.
Wood and Nopoulos explained their strange findings by clarifying that female brains mature and develop around one or two years earlier than male brains. This means that girls undergo pruning (the reduction of gray matter volume, which is an important process in brain maturation) at a younger age, hence the smaller, more mature SG in girls compared to boys.
But they weren’t out of the water yet. To add to the admitted complexity of their findings, Wood and Nopoulos used a questionnaire in each study to measure the self-ratings of masculine and feminine traits in each of the participants, using questions about their interests, abilities, and personality type. They found that much like the scores on the social cognition test, higher levels of identification with feminine traits, such as preference for masculine or feminine clothes, careers, hobbies, and interpersonal styles, correlated with larger SGs in adults, and smaller SGs in girls.
So what does all this mean? It appears that brain structure isn’t just a matter of being a man or a woman, since psychological gender—the possession of masculine or feminine traits—appears to be correlated with SG size. So are feminine people simply more social? Do they have more friends on Facebook? And can they attribute it all to the sizeable SG sitting in their foreheads?
The research made an important point in showing that behavioural differences can be biological without being hard-wired. In this case, women and men can show brain structure–related differences in social cognition, but it remains unclear whether the discrepancy is based on genetic factors determined from birth. What’s more, the studies address the issue of whether psychological gender can influence brain structure. Wood and Nopoulos concluded that there is a complex relationship between femininity, social cognition and SG size, suggesting that social learning may contribute to brain structure. But some questions still arise from these conclusions, namely, how might stereotypes influence performance on social cognition tasks?
Dr. Michael Inzlicht, a psychology professor at UTSC, researches how negative stereotypes affect cognitive and emotional processes in people belonging to a stigmatized group. For example, “If a woman is aware that there are negative stereotypes about her group—say, that men are better than women at math—if she takes a math test, she might risk underperforming in that task, because now, not only is she thinking of the test items, but she’s also worried about confirming the negative stereotype,” says Inzlicht.
This phenomenon is called stereotype threat and is well studied in social psychology. Individuals from a stigmatized group may underperform because of the anxiety from belonging to a negatively stereotyped group. “The important part about the phenomenon of stereotype threat is that it can affect all groups, even dominant groups in society, because […] every group out there has some stereotype that exists about them, and there’s bound to be at least one of those that’s going to be negative,” Inzlicht explains.
But what does stereotype threat have to do with the research by Nopoulos and Wood? One study examined the stereotype that men are not as emotionally sensitive as women: when given a task to judge the emotional expression on another person’s face, they tended to perform poorly when the negative stereotype was active in their minds.
This raises an important question: are men’s lower scores in social cognition tasks the result of a negative stereotype, or did the biological differences in performance provide the seed for the stereotype to proliferate? What’s more, the fact that people with more conventionally masculine traits performed most poorly on the social cognition task suggests that gender stereotypes might indeed be at work, since more “masculine” people would identify most with this particular male stereotype.
It’s a difficult question, and one that’s not easily answered. While many people—including a number of researchers—would like to say that there are inherent differences between male and female cognition, there’s a chance that these differences are influenced by the social processes that lead to cultural impressions about specific groups.
“It’s impossible to tell unless stereotypes are gone,” says Inzlicht. “There’s no doubt in my mind, at least, that stereotypes contribute to this difference. Whether they account for all of it is difficult to determine.”
