Male and Female Brains

My trek through the literature on sex differences continues. These podcasts from NeuroGenderings III are interesting, especially the talks by Anne Fausto-Sterling and Rebecca Jordan-Young.  The Jordan-Young talk led me to version 2, which she gave at a symposium in honor of Fausto-Sterling (video here).  And from there, I was led to two papers--"Male or Female? Brains are Intersex," by Daphna Joel; and "Reframing Sexual Differentiation of the Brain," by Margaret McCarthy and Arthur Arnold (which I haven't read yet).  A nice break in the technical slog: there's also this TED talk by Daphna Joel.

The Joel paper and talk (parts of which are highlighted by Jordan-Young) makes me wonder about several things.   First, a philosophical question.  What would you need to find out about brains to say there is a male brain and a female brain?  Joel is emphatic that there is no such thing as a male brain or a female brain because there aren't two forms for brains, just differences in averages on hundreds of parameters.  Plus, a person can score "female" on one parameter but "male" on another--the scores don't line up consistently. Plus, the scores on various parameters can change over time, for one individual, due to environmental factors like stress.  But what about the reproductive machinery in the brain, which takes different forms in males and females?  Donald Pfaff writes, "The most striking sex difference is that the female hypothalamus can command the pituitary to put out pulses of hormones that will cause ovulation by the ovary, whereas the male hypothalamus cannot do that."  (Man and Woman: An Inside Story kindle loc. 586).   How is it that this difference in the hypothalmus doesn't mean that there actually is a male brain and a female brain?  I have to surmise that "male brain" means, to Joel, a brain that's male through and through.  A difference in one part won't do.  Likewise for "female brain."

But why?  There are male and female bodies, right?  And they're male and female because of differences in certain parts. Among other things, males and females have different gonads.  You wouldn't say "there are no male and female bodies" just because male and female kidneys, livers, hearts, gall bladders, and so on, don't take different forms.  So I am honestly puzzled by this insistence that there are no male and female brains.

I suppose what's going on here is that folks like Joel want to disabuse people of a popular error--the belief that the brains of men and women are different through and through.  That is not the case (if Joel is right), though certain parts are different (if Pfaff is right).  I would think that, using language carefully and literally, the difference at the level of parts means there are male and female brains.  It's just that this isn't the super big deal some people say it is--like The Female Brain author Louann Brizendine.

Now for an empirical question. Jordan-Young embraces the part of Joel's paper that says it's impossible to say how one individual will score on one sex-dependent parameter, based on how they score on another. The various parameters don't necessarily line up, making each individual's mind/brain a pink, blue (and other) mosaic.  What I wonder, though, is what kinds of covariance you find between the different parameters.  Given a person scoring high on aggression, is there a higher probability that they will score high on other "male" traits like willingness to take risks?  If a person scores high on compassion, is it more probably they will score high on sensitivity and squeamishness?  This is really an important question for understanding sex, particularly if you want to evaluate a point Jordan-Young makes many times: sex is not a mechanism.  If there's even just pretty good covariance, it makes you think sex probably is a mechanism.  Something's got to be making these traits tend to cluster together (if they do).

The covariance question is an important question for me because I'm trying to think about the way parents react to the sex of their children, on ultrasound or at birth. If the mosaic of traits for each individual shows no internal coherence--from one tile you can't predict the others at all--then we ought not think much of it when we hear "it's a boy!" or "it's a girl!".  But if there's quite a bit of internal coherence--from one tile you can predict the others pretty well--then the natal sex of your child tells you more.

Questions, questions.  In another life I will study the neuroscience of gender full time, because it's a vast subject and awfully interesting.


What Sam Harris Said

Lately I've been working on the gender chapter of my book about parenthood. Because I've been knee deep in the literature about gender differences, I've been intrigued by the recent Sam Harris dust up in the blogosphere.  Michelle Boorstein, a Washington Post reporter, gives this account of an interview she did with Harris at a Center for Inquiry event in DC:
I also asked Harris at the event why the vast majority of atheists — and many of those who buy his books — are male, a topic which has prompted some to raise questions of sexism in the atheist community. Harris’ answer was both silly and then provocative.
It can only be attributed to my “overwhelming lack of sex appeal,” he said to huge laughter.
“I think it may have to do with my person slant as an author, being very critical of bad ideas. This can sound very angry to people..People just don’t like to have their ideas criticized. There’s something about that critical posture that is to some degree instrinsically male and more attractive to guys than to women,” he said. “The atheist variable just has this – it doesn’t obviously have this nurturing, coherence-building extra estrogen vibe that you would want by default if you wanted to attract as many women as men.”
So, angry criticism of bad ideas: intrinsically male.  Nurturing and coherence-building: intrinsically female.  Plus, a tentative explanatory claim: the gender difference "may be" the cause of Harris having more male readers and atheism having more male adherents.

Many feminists in the atheist community think what Harris said was sexist and contemptible. If you look around, you'll see people accusing him of "gender essentialism,"  seeing women as "biologically inferior," and all manner of other screw ups.  One person's response is a simple "fuck you."  The demonizing of Harris says a lot about why feminism has become such a divisive topic among atheists, skeptics, and such. A certain kind of feminist does regard any assertion of intrinsic gender differences as anathema, taboo, sexist, and grounds for dismissal.  But that kind of feminism just isn't compatible with reasoned, science-based inquiry.  The scientific literature does not, just does not, support the idea that all assertions of intrinsic gender differences are beyond the pale, signs of sexism, or taboo.

To see this, you might want to start with the book Touching a Nerve: Our Brains, Our Selves, by the philosopher Patricia Churchland.  A whole chapter of the book is devoted to arguing that males are more aggressive than females, because of brain differences.  She sums up at the end:
To a first approximation, human males and females display differences in aggressive behavior that are linked to male and female hormones, though these behavioral dispositions can be modulated by the cultural matrix.

Churchland relies heavily on Man and Woman: An Inside Story, by Donald Pfaff, for her account of how hormones create innate differences.  This is a rather technical book that covers a vast amount of research about hormones and fetal development.  Aside from being tough going, it's also quite focused on rat and mouse models.  A more digestible and people-centered book is Brain Gender, by Melissa Hines.  Hines strikes me as a model of restraint, yet she does assert that there are innate brain differences. Again, the claim is that hormones make the difference, causing boys to be (among other things) more inclined to rough and tumble play than girls.  She says the research backing up her picture of brain gender amounts to over a thousand studies.

All that at least shows one respectable position is to assert innate differences, but if you're still not convinced, there's Pink Brain, Blue Brain by Lise Eliot, who argues that there are very small but real innate differences between boys and girls.  Note: she's not at all a Louann Brizendine,  one of these "vive la difference" authors who seize upon and exaggerate every difference they can get their hands on. This is cautious, restrained science that finds small differences and only small differences.  Another author of the same character is Janet Hyde, who's very critical of authors like Brizendine, but still does find small differences--as she explains in this talk.  Even an outright feminist and gender social constructionist like Anne Fausto-Sterling acknowledges small innate differences and cites Hyde with approval.  See, for example, her book Sex/Gender.

No discussion of this literature would be complete without a mention of critics like Cordelia Fine, author of Delusions of GenderThe subtitle sums up her attitude:  "How our minds, society, and neurosexism create differences."  She does appear to take the ultimate social constructionist position--that all apparent gender differences are created, not found.  By all means, she does an effective job of dismantling "vive la difference" authors like Brizendine and Simon Baron-Cohen (author of The Essential Difference).  Her book includes a very illuminating chapter on how non-innate factors like stereotype threat can create significant differences.  This is definitely a book worth reading, but for my money, it does not undermine all of the research on innate gender differences.  And neither does a second book of the same sort--Brain Storm, by Rebecca Jordan-Young, which does have some compelling chapters and sections.  Both Fine and Jordan-Young are worth reading, but effectively criticized in this review.

All in all, I think people could read the gender differences literature and come away with different conclusions, which is why the science of gender is lively and interesting.  What is really clear, though, is that there's nothing taboo or shocking or offensive or sexist about thinking there are some innate gender differences.  And that brings us back to Sam Harris. As a neuroscience PhD, I imagine he's familiar with some of this literature.  He's right to protest (here) against being accused of sexism for thinking (along with the likes of Patricia Churchland!) that there are some innate differences between men and women.

But let's cut to the chase. Do I entirely agree with what Sam Harris said?  I agree that men are innately a bit more aggressive (on average) and women innately a bit more affiliative (on average).  I'm less sure about Harris's tentative explanatory hypothesis.  It's tricky to say how a set of inborn differences must manifest themselves in the real world.  Supposing women are less aggressive, are we really to believe that they're aggressive enough to be half of law school students, but not aggressive enough to be half of Sam Harris's readers?  That's not all that plausible.  To me it seems as if something else is going on here, something more complicated.  Women can be aggressive enough for doing philosophy and debating religion, but have less room on their "mattering maps" for those activities (to use Rebecca Goldstein's phrase).   But why?  Is it for innate reasons or because culture steers them in certain directions and not others?  I really don't think we know.