Last week one of the big science stories to hit the news was the publication of a brain scanning paper that purportedly used science to back the popular stereotype that men are better than women at navigation and various other action-related tasks, and women are allegedly better at all that intuitive stuff.
Is this news true? Who knows? The stories don’t offer any real backing for the claim and there seemed to be rampant confusion between chatty speculation and experimentally-grounded observation. .
The claim comes from a group at the University of Pennsylvania and Children's Hospital of Philadelphia. The researchers used a brain scanning technique called diffusion tensor imaging (DTI) on a sample of 521 female and 428 male subjects. The results were published in the Proceedings of the National Academy of Sciences (PNAS). A press release from Penn said the team found "striking" sex differences in neural wiring, with women showing more connections between hemispheres and men more connection from the front to the back parts of the brain.
In the press release, the researchers are quoted speculating that the differences they observed explain why men are better at “single tasks, such as cycling and navigating” and women are better at memory tasks and "social cognition skills".
No evidence is presented in any of the stories or the press release that men are in fact better at these things, or that the brain scans have anything to do with these differences if they indeed exist.
Here's the lede from The Telegraph :
It is something that men and women have long suspected – their brains are wired differently.
Here's the Guardian:
Scientists have drawn on nearly 1000 brain scans to confirm what many had surely concluded long ago: that stark differences exist in the wiring of male and female brains.
Those ledes tell us more about the writers (and the press release writer) than about science or the way the world works. Sure, a you may be a better map reader or car-parker than your spouse, but it’s an error to assume that’s due to some universal sex difference.
Most of the stories I read failed to answer the most a basic, critical questions needed to determine what, if anything, presented in this paper is newsworthy, interesting or true.
One glaring omission was the size of the observed sex difference. The press release said it was “stark” and “striking” but there was nothing presented in the stories to back it. The stories for the most part presented various sex differences as clear-cut, as if women were always good at intuitive, emotional activities and men always good at navigation. Surely we’re talking about some subtle difference in the averages.
I did find one answer, not from a news story but in a subsequent commentary piece by psychologist Cordelia Fine, writing in The Conversation:
Even the much-vaunted female advantage in social cognition, and male advantage in spatial processing, was so modest that a randomly chosen boy would outscore a randomly chosen girl on social cognition – and the girl would outscore the boy on spatial processing – over 40% of the time.
Even when there's a large difference in averages, as with height, we don't say men are tall and woman are short, or suggest that women are any less feminine if we happen to be tall. And so it felt misleading to me to read that men’s brains allegedly work better for X and women’s better for Y. Here’s CBS.com:
….men have more neural connectivity from the front to back of their brains and within each of the hemisphere than women. Theoretically, this means their brains are more adapted towards tasks involving perception and coordinated actions.
Women, on the other hand, have more wiring between the right and left hemispheres of the brain, making them more adept at communicating, analyzing and having better intuition.
Also missing from the stories I read was any explanation for why the researchers could so confidently connect the physiological difference they observed with alleged behavior differences, interpreted by some reporters to include men excelling at navigation, parking and throwing (isn't that attributable more to differences in the arm and shoulder?), and women being better at remembering anniversaries.
The press release says that the researchers also gave their cohorts various psychological tests – "face memory, spatial processing, attention, social cognition" and the like. But neither the press release nor any of the stories offered a convincing argument that these tests are connected to the brain scans or to the real world.
From my reading there’s a leap connecting the brain scans to the psychological tests, and another leap connecting the psychological tests to the real world, and a third leap in assuming that stereotypes about navigation and “intuition” are remotely true.
Another unanswered question was whether these brain connections are really "hard wired". I thought some kinds of connectivity in the brain change in response to learning new skills, such as playing a musical instrument. Why the connections imaged by the Penn team were “hard wired” went unexplained.
Many of the news stories also made it sound like these researchers were just imaging brains when the "striking" sex differences jumped out at them, but in fact some memebers of the team have been looking for sex differences in the brain for years. Here's a story about their discovery of male-female brain differences back in 1995.
A blog called Neuroskeptic did follow up with some good critical observations, and a Wired blog called Brain Watch answered a number of the questions I'd posed. According to blogger Christian Jarrett, the size of the effect was small, it concerned averages, and the scientists had no evidence that the differences they observed with their scanning technology corresponded to any differences in skills or talents, except for some vague and outmoded ideas about brain hemispheres.
The way Verma and her colleagues have arrived at the idea that their results support gender stereotypes about map reading, and so on, is via a logical mistake known as “reverse inference”. They looked at where in the brain they found wiring differences and then they’ve made assumptions about the functional meaning of those differences based on what other studies have suggested those brain regions are for.
It’s fair enough that the researchers speculate in quotes and in their press release. We like scientists to loosen up, be human, and chat with us. Isn’t it the reporters’ job to separate evidence, observation, theory, guesswork and chit-chat?
And I couldn’t help wondering if the spin Penn put on the press release got so widely amplified because it allowed writers to indulge in repeating stereotypes that would otherwise seem sexist if not allegedly backed by science. And yet, here in the U.S. anyway, the more common navigation-related stereotype is not that men are better than women at reading maps but that they’re reluctant to ask for directions, even if sometimes they should.