Sandra Witelson has spent much of her career studying the relationship between brain structure and function, and the differences in these between men and women.
A neuroscientist from the Michael G. DeGroote School of Medicine at McMaster University in Hamilton, Ontario, Dr. Witelson has assembled a massive collection of brains for research and is known for studying Albert Einstein's brain and what made it unique.
She sat down with The Wall Street Journal's Rebecca Blumenstein at the Journal's Women in the Economy conference last week to discuss how brain differences can affect the skills, behavior, thinking and aspirations of men and women, and how that might relate to their careers.
Here are edited excerpts of their conversation.
Rebecca Blumenstein: You have found significant differences between male and female brains. Could you explain what those are?
Sandra Witelson: The very first one that I reported [in a 1976 paper] was that when a young boy is doing things relevant for reading, he is using one side of his brain. He uses the other side for non-reading skills. In a girl, there is much more of a bilateral involvement in these skills. So, in the normal six-year-old, the brain is organized to do the same task, but it's organized in a very different way.
RB: Could you go a little bit more deeply into the innate differences? When we spoke earlier, you had said that there's a finding that there are 12% more brain cells in the female brain.
SW: Some of you may know that there is a structure called the corpus callosum. It is the big highway track between the left and the right hemispheres. What we were able to show is that there is a part of this corpus callosum that is larger in women in the back part of the brain, which is the region where language representation is. This may be part of the substrate that gives an advantage to earlier speech, to better ability to learn phonics, to verbal fluency in women. In another study, we found that in the language region, there were more brain cells in women than in men.
Other laboratories have shown that boys' frontal lobes, which are important for judgment and planning of our behavior, mature at a slower rate than girls' frontal lobes. As a consequence, there is more risk taking and more behavior that shows poor judgment in boys than in girls in the adolescent period.
Another example is the response to stress. In animals, it has been shown that in acute stress situations, the male brain, in the hippocampus, which is in the middle of the brain and is crucial for new learning and memory, sprouts more synapses and dendrites, which facilitate learning. In contrast, there is a decrease in the amount of sprouting of these interconnections among neurons in a female during periods of acute stress. It turns out that chronic stress may be biologically responded to more adaptively in the female than the male brain.
There is another part of the brain, the amygdala, that becomes active if there is a negative response to emotionally arousing stimuli. The amygdala is connected physiologically to different parts of the brain in each sex, and I think this has tremendous implications for our behavior.
In men, the amygdala communicates very strongly to motor parts of the brain, which means behavior that is directed outward to the external milieu. And in women, the amygdala is connected very strongly to the hypothalamus, which looks after our internal environment—our breathing, our heart rate, etc.
Innate or Acquired?
RB: A few years ago, Larry Summers got into a lot of hot water when he said that innate differences between men and women might be one reason fewer women succeed in science and math careers. But you would say that we need to acknowledge these differences.
SW: Yes, I would say that. No one gets upset that there is an innate difference in lung capacity between different groups of people. No one seems to be that upset when there are different motor skills and athletic skills. But when it comes to our most revered organ, namely the brain, people do not like to think that there is something innate, immutable. But the brain is an organ of the body like any other organ. So to think that there are no innate differences is an incorrect assumption.
What is very important is to try to get the full picture of why women and men are differentially distributed in the work force in many fields. It's not only trying to understand the organizations and the culture and dealing with the social environment, external milieu, but it is essential to try to understand where some of the differences that you all know and see come from. It is important to celebrate these differences and for the people in authority, whether they're men or women, to understand that, on average, women may bring different styles of thinking, different approaches, different skill sets to their job and should be hired for those reasons and not to fill any quota.
The other advantage would be for women to understand who they are.
There is a very informative study by some psychologists who studied thousands of children who scored in the top one percentile on the SAT, Scholastic Aptitude Test, on mathematics when they were in elementary school. There were a lot more boys, but there still were a lot of girls. These kids were followed 20, 30 years later. There were fewer physicists among the women. There were fewer mathematicians. There were more administrators among the women. But I think more revealing was that when they were asked to talk about what is important in their life, what their priorities are, there were huge differences.
For women, they are statistically more interested in having close relationships with parents, having a part-time career, living close to parents and relatives, period. Men, on the other hand, more frequently said they want to have a full-time career, and they wanted to invent and create something.
So my point is that the kind of aspirations that men and women have may be very related to some of the biological drives and needs that we have inherited as Homo sapiens over the development of our species.
This story originally appeared on WSJ.com.