Brains!

This weekend, my mom mentioned seeing something on TV about female and male brains. I know that I have a sort of allergic reaction to gender essentialism (which I am using to refer to the belief that men and women are/must be different in many respects that have nothing to do with reproduction and that these differences arise naturally, perhaps inevitably, from genetics/biology), but the entire pop psychology view of the brain, including the sweeping categorizations that are made on the basis of gender, is pretty whack.

On the show my mom was watching, some doctor (note: not a neuroscientist) brought up ye olde "men and women have different brains" chestnut, focusing on the fact that men's brains are more "compartmentalized" to explain some differences in social behavior - if I recall correctly, in expressing feelings or something like that.

I am going to take this "compartmentalized" brain language to be referring to hemispheric lateralization - the idea that the right and left hemispheres of the brain are specialized for (or show processing advantages in) different cognitive functions - and the extent of a person's connection between the hemispheres in terms of neural connections within the corpus callosum, the 250 million nerve fiber connection that allows the two sides of the brain to communicate.

(I am not going to interpret "compartmentalized brain" in its other common meaning of "men store their ideas about sex, love, work, etc., all in different file drawers in their head" because I don't know of a respectable memory model that would support that and the interpretation of "compartmentalization" as emotion suppression is not something I'm at all prepared to address from a brain perspective.)

One thing we do know: the average woman's brain is smaller than the average man's brain, since brain size is correlated with body size. This causes problems in understanding whether some observed gender differences, such as the shape of the posterior section of the corpus callosum, are really due to gender or are simply a matter of brain size. (Also, of course, neuroscientists have not actually found functional differences that correspond to every anatomical difference, so it may not even matter.)

What about the popular notion that men's brains are more "compartmentalized" or show a greater degree of lateralization than women's brains do? This is a continuing source of debate, with various studies showing women (and left-handed men!) to be less lateralized than right-handed men, showing no differences between the sexes, or even showing women to be more lateralized. One review of the literature found that between 5% and 15% of studies have found women to be less lateralized than men are and further noted that even when the differences reach the level of statistical significance, gender accounts for about 1% or 2% of the variability in lateralization. I would not say that is explaining much of anything at all, and especially not about stereotypically male and female social behavior.

Also, note that I used the phrase "show processing advantages" when talking about the two hemispheres of the brain advisedly. People used to think that cognitive functions were very localized to particular parts of the brain, but we now know that there are often multiple ways the brain can accomplish the same function and that many functions are much more generalized than previously thought. Once you get past the popular media summaries of things like "the left hemisphere is for language, the right hemisphere is for spatial processing," you find it's a lot more complicated. Maybe the left hemisphere (LH) is more analytic and the right hemisphere (RH) is more holistic in its processing. But maybe it's more that the LH has an advantage in processing local information and the RH has an advantage with global information. And when it comes down to it, the hemispheres are a lot more alike than they are different.

My mom asked an astute question: Even if there are differences in the brain, how do we know that they are inherent and haven't changed over a person's life? I don't know how to answer that question. Since we're generally studying adults, not infants, to me it does require a leap to infer that differences are genetic, especially since there are plenty of well-documented cases of people's brains "reorganizing" after being damaged, for example.

One thing that is lost in the mass media discussion of neuroscience is that brain science is not straightforward. There are a wide array of different methodologies, each of which is problematic and requires making interpretive leaps. (This is why neuroscientists place so much value on converging evidence from multiple methodologies - animal studies, neuroimaging, electromagnetic recordings, studies of people with brain damage, behavioral studies, studies of neurotypical people, etc.) A lot of what is being measured is very indirect - for instance, functional MRI (fMRI), which is one of the more advanced methods, involves measuring blood flow and blood oxygenation in different parts of the brain and using those measures to infer the activity levels of those brain areas.

In any event, making categorical statements about male and female differences on the basis of linking some perceived discrepancies in behavior to tiny differences in brain anatomy or neural activation rather than, say, socialization is pretty drastic...especially when these supposed behavioral differences are questionable to begin with. (My mom brought up the finding that despite widespread belief to the contrary, women don't actually talk 3 times as much as men do.)

I know that since I study social psychology, I am very interested in and highly aware of how much influence environment and social context has on people's behavior, perhaps to the extent of prejudging some biological/genetic arguments as unlikely without giving them a fair hearing. But all these variants on "Men are from Mars and Women are from Venus and because God/Nature/Evolution made them that way!" gets tiresome. And yeah, that does include the work of Simon Baron-Cohen, whose "female brain = empathizing, male brain = systemizing because of prenatal testosterone levels" thing is not bearing out perhaps as well as it might in the general (neurotypical) population.