High Crockalorum from the LAB
September 18, 2007
Yesterday, Heidi W a US forum member . sent in a note about the presentation that Dan Hodgins made to an Early Childhood Education group in her large urban school district ("How big is your crockus?", 9/17/2007). Much of his talk was the standard stuff of current pop neuro-indoctrinology ("science has revealed that boys' brains are made of snips and snails and puppy-dog tails"), but one bit stuck out: the idea that a brain structure called "the crockus" is four times larger in girls than in boys.
Now, I'm used to seeing the pop neuro-indoctrinologists misrepresenting or even inventing numbers, exaggerating differences, and generally misusing science to shore up weak arguments about social policy. But this is the first time, as far as I know, that someone has actually made up a whole new brain area.
In fact, the idea that someone would actually fabricate "the crockus" as a neuro-anatomical neologism was so unexpected, so far beyond the boundaries of my imagination, that I misinterpreted Heidi's note. I thought "crockus" was her attempt to render some odd pronunciation that Hodgins used in his presentation.
But she quickly corrected me, and sent in a scan of (parts) of his handout, which was the take-away paper form of his PowerPoint slides. Here's the crucial slide:
His next slide tells us that (because of their smaller Crockus) "boys see the whole but not the details". And then he showed the audience a lateral view of the brain -- Heidi also sent a scan of the handout version:
And she did a bit more research:
The drawing of the brain is not labeled on the handout, and it wasn't labeled in Hodgins' PowerPoint presentation, but the drawing indicates that it's from BrainConnection.com and I just located it here.
Hodgins referred to the small royal blue area, which is labeled "pars opercularis" on the web site PPslide, and he said that's the size of the crockus in males, and he referred to the motor cortex (somewhat lighter shade of blue) and said that's the size of the crockus in females.
This is truly strange stuff. I feel like I'm in a magic realist novel that's slipped slightly out of editorial control.
But I have a theory. Maybe back in 2003, Prof. Hodgins was talking with some of his drinking buddies, and the conversation went something like this:
Hodgins: Those education professionals, they're so worried about sex differences and so wowed by neuroscience, you can show 'em a picture of the brain and tell 'em any crazy thing about how brain scans show boys are different from girls. And they not only believe it, they pay you. Fly you out, nice hotel, per diem, the works.
Drinking Buddy #1: OK, they're desperate and they're credulous, but you got to make it plausible.
Hodgins: Nah, you take a random brain picture and any stupid made-up words and numbers, they'll swallow it like ice cream.
Drinking Buddy #2: Come on. You got to do a little reading, anyhow, you can't just tell them, oh, the "crockus" is four times bigger in girls and that's how come they're like better with details while us guys deal with the big picture.
Hodgins: Sure I could, absolutely.
Drinking Buddy #1: $500 says you're full of it.
Hodgins: You're on.
This theory is surely false. Maybe Prof. Hodgins just mis-remembered pars opercularis as crockus. Or ....
No, I give up. I'll just spoil the joke, in my usual heavy-handed way, by citing what's actually known about sex differences among school-age children in the brain region that Hodgins seems to have been talking about.
Let's take a look at R.E. Blanton et al., "Gender differences in the left inferior frontal gyrus", Neuroimage, 22(2):626-636, 2004.
This study examined frontal lobe subregions in 46 normal children and adolescents (25 females, mean age: 11.08, SD: 3.07; and 21 males, mean age: 10.76, SD: 2.61) to assess the effects of age and gender on volumetric measures as well as hemispheric asymmetries.
Here's their Fig. 8 "Gender Differences" bottom graphs
which they explain as follows:
Total intracranial volume, total gray matter, and total white matter were significantly larger in boys compared to girls (F = 11.63, P = 0.001; F = 16.17, P < 0.001; F = 9.59, P = 0.004, respectively). In addition, total left gray matter volume was found to be significantly larger in boys (F = 7.58, P = 0.009).
After covarying for total intracranial volume, male subjects were found to have more gray matter in the left IFG (F = 9.14, P = 0.004), a trend for a significantly larger left IFG relative to girls (F = 6.38, P = 0.016), and a trend for increased asymmetry in total right white matter as compared to total left (F = 6.24, P = 0.017).
Let me point out here, again, is that the distributions are heavily overlapped, and that most of the subjects are in the overlapped region. The sex differences are interesting and worth further study, but it's nuts to prescribe on the basis of such evidence that our educational systems needs to treat boys and girls as if they were completely separate species.
Posted by Mark Liberman at September 18, 2007 06:17 AM