There’s a popular myth that men and women have different types of brains. What’s the truth in this statement, and how significant are the differences? Professor Indre Viskontas, Ph.D. discusses this myth in her course Brain Myths Exploded. Below is an excerpt from lecture five of the series.
Women’s Brains vs Men’s Brains—The Amygdala
The amygdala is larger in men than in women. The hippocampus is larger in women than in men. The corpus callosum… well, it depends on how you measure it. Each of these regional differences is in fact far more complicated than it first seems.
Let’s start with the amygdala, an almond-shaped structure that plays a key role in the emotional modulation of memory. The amygdala is why we remember details of events that were very emotional: where you were when you heard about 9/11, for example.
We used to think that the amygdala was primarily concerned with negative emotions, especially fear. But with more data, there is now good evidence that the region leaps into action when we are experiencing strong emotions, regardless of their valence. And when the amygdala is active, we tend to form stronger and more vivid memories of whatever we are experiencing.
You might have heard the term flashbulb memory: this is a characterization of a memory that you might have that seems to be particularly vivid – as though a moment in time has been captured by the flash of a camera. We’ll consider the accuracy of flashbulb memories in a later lecture, but for now, suffice it to say that the amygdala plays a role in telling the hippocampus, the region that lays down new long-term memories, to pay attention.
Learn more: How Different are Male and Female Brains?
There are studies documenting behavioral differences in the recall of emotional events by men and women: women seem to have stronger and more detailed memories of emotional events and are able to bring them to mind more quickly. So the idea is that the increase in memory strength that happens with emotion is bigger in women than in men, on average.
And while this memory enhancement sounds like a benefit, it might also be one of the reasons why women tend to be diagnosed more frequently with disorders like depression, anxiety, and PTSD. And there’s some evidence that memory for things that happened just before an emotional event is worse in women than in men.
You might also have heard that men and women differ in terms of how their brains are ‘wired’. Usually, when we talk about wiring, we mean how the different parts of the brain are connected. And you’ve probably heard the idea that the two hemispheres are more tightly connected in women than in men.
But on average, women’s brains have proportionally more gray matter than men’s brains and men’s brains actually have a larger percentage of white matter. White matter is the stuff that connects neurons. Moreover, when we look at the corpus callosum—which is the largest bundle of white matter in the brain—the connectivity story gets even more complicated.
The corpus callosum is the fiber tract that joins the left and right hemispheres in the brain and is often cited as one of the regions that shows robust sexual dimorphisms: women tend to have larger and more bulbous corpus callosa than men, and this finding has been interpreted as showing that women have more communication between hemispheres, and think more holistically. In 1982, a study published in the eminent journal Science first reported this difference.
Then, in 1991, a second paper came out in the highly reputable Journal of Neuroscience indicating that it’s more bulbous in women, but more tubular in men and the total area is the same.
Then, a meta-analysis in 1997 found no significant sex differences across 49 studies of the corpus callosum.
Finally, a study in 2003 in India showed that in Indian brains, the corpus callosum is longer in males than in females and that it increases with age in males, but not in females.What these studies show is that measuring brain volumes, even in the same region, is complex and that variability with age, culture, and other factors muddies the waters significantly. And, the corpus callosum seems to be especially prone to neuroplasticity: musicians, for example, after much training, have been shown to have larger corpus callosa than non-musicians.
And yet, when those first studies came out in 1982, many scientists and journalists were quick to tell a good just-so story: of course women have greater connectivity between their hemispheres – they think more holistically and intuitively. And of course men’s brains are more modular – they look for solutions to problems and focus on one thing at a time.
Some of these differences in connectivity have also been used to promote the left/right brain myth: that because women are supposed to have greater interaction between the hemispheres, they have greater access to the non-dominant, intuitive and emotional right hemisphere, while men are more dominated by their logical, analytical left hemisphere.
But the truth is much more complicated and nuanced, of course.