Yesterday was a fantastic day for one group of researchers (Ingalhalikar et al.)* who specialize in looking at sex differences in the brain. Their paper was popularized the way a cure for cancer would be, and that is because the authors made de-lic-ious comments about their study as proving that the hardwiring differences between male and female brainz had been found, that they are GIGANTIC!!! and they gave us all PICTURES which show this so very very clearly.
Then, also, the differences were of the expected type! Women seem to have brainz built(!)/hardwired(!) for social cognition (which all the nasty commentators in all the comments threads turned into women talking and gossiping so much) and better memory (which those comments argued was all about never forgetting that you, a guy, forgot her birthday), whereas men seem to have brainz built for clear perception-action patterns and also seem to have better motor skills (which I thought was about stuff like muscle speed but which the popularization believe are about men's superior ability to read maps or the never-dying myth that men are better drivers than women).
On the other hand, menz are completely incapable of multi-tasking!
Now would you like some fries on the side? The hash I made for you above wasn't made by me. It was made by one of the researchers of the study, Ragini Verma, in several published interview comments. She mentioned ideas such as that men might be better map-readers and that women, in turn, might be better listeners or better at multi-tasking!
But the popularizers haven't actually helped! And John Tierney and David Brooks are probably still feverishly writing away, so we are going to get more fun and games for many, many weeks. If (or when) the flaws in the current study are revealed and the results changed, not a single popularizer will care to put any corrections on the front page of their newspapers. For that I'm willing to bet a Ferrari.
Goddess but I love-hate this shit! Let's step back a bit, to sort a few things out.
First, this particular study is an attempt to map out gender or sex differences in the human brain's structure, not in functionality, by using a fairly recent imaging method. I'm a babe-in-the-woods when it comes to such complicated research methods, but after spending most of yesterday looking for information, what I think the study tried to measure (and correct me if I'm wrong) is the water-permeability of the white matter in the brain. The idea might be a bit like finding paths in the woods? It's not the case that you cannot walk off the path but the paths show where you mostly use to walk. Or finding rivers and brooks. Water could travel anywhere but it mostly goes to those furrows in the soil it is used to. So if these maps of connectivity show a sex difference then it could be that men and women use their brainz in different ways, on average.
Now, as far as I get it, ALL this study could try to establish is whether those paths or rivers look the same in the brainz of men and women or whether they look different. The comments about how the maps of women's paths prove that women are good in multi-tasking and men not or how the maps of men's paths prove that men are good at driving and map-reading and women are not, all those seem to be assumptions lumped on top of whatever the brain pictures (SOOO pretty) show. They are added by Ingalhalikar et al. who even conclude like this (from the study itself, behind a pay-wall):
Overall, the results suggest that male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.
All that looks like making much bigger assertions than the data confirms. What the pictures (to be talked about later) seem to show is that the male brain (typical male brain?) we are shown appears to have paths which largely go from the back of each brain hemisphere to the front of that hemisphere or the other way, wheres the female brain (typical female brain?) seems to have paths which more often cross from one brain hemisphere into the other. But WHAT those paths imply about, say, communication between analytical and intuitive processing modes (the stuff which people in many of comments threads interpreted as meaning that men are logical, women emotional) is a whole different kettle of fish.
For instance, one recent study suggests that the left-brain-logical, right-brain-creative thinking we have all had for breakfast for decades might not be that tasty anymore:
Bolds are mine. So the point is that researchers can disagree about where those paths go or that perhaps researcher don't necessarily know where those paths go and why.
Second, the whole study and its treatment is a great breakfast barbeque of things designed, constructed, wired, hardwired and hardwired! Just look at the titles of some of the popularizations:
Not all yesterday's discussions of the study were like that. This one is critical of the study. What's the funniest thing on earth, right now, is that the paths one might make in the brain by either inheriting them or by walking a certain way a lot are just assumed to have been inherited. In reality they might have been there when one was born, but there is lots of evidence telling us that people can make new path-works in their brains and that people can be trained to do that. The brain, in general, has been found plastic (flexible, capable of learning new pathways).
The fault for concluding something from the study which it cannot actually prove (that the observed differences in brain structure are "hardwired") lies firmly in the researchers' lap. The study uses the words "designed" and "wired" a lot:
On the head motions: This study (Figure1) shows a sex difference in the amount of head motion during the imaging. Head motion is greater for males than for females. Moreover, the effect of greater average head motion was found to be associated with apparent decreased functional connectivity in large-scale networks and apparent increased functional connectivity between the left and right motor regions. As far as I can figure out, that is exactly what one would expect in the Ingalhalikar et al. study which seems not to have taken head motion into account at all. At the same time the authors of the article studying the effect of head motion find its impact to fairly small on the results in their study. On the other hand, they state:
Given this, the Ingalhalikar et al. study should bere-run reanalyzed with controls for brain size and head motion before its results are discussed.
For instance, one recent study suggests that the left-brain-logical, right-brain-creative thinking we have all had for breakfast for decades might not be that tasty anymore:
The preference to use one brain region more than others for certain functions, which scientists call lateralization, is indeed real, said lead author Dr. Jeff Anderson, director of the fMRI Neurosurgical Mapping Service at the University of Utah. For example, speech emanates from the left side of the brain for most right-handed people. This does not imply, though, that great writers or speakers use their left side of the brain more than the right, or that one side is richer in neurons.
There is a misconception that everything to do with being analytical is confined to one side of the brain, and everything to do with being creative is confined to the opposite side, Anderson said. In fact, it is the connections among all brain regions that enable humans to engage in both creativity and analytical thinking.
"It is not the case that the left hemisphere is associated with logic or reasoning more than the right," Anderson told LiveScience. "Also, creativity is no more processed in the right hemisphere than the left."
Bolds are mine. So the point is that researchers can disagree about where those paths go or that perhaps researcher don't necessarily know where those paths go and why.
Second, the whole study and its treatment is a great breakfast barbeque of things designed, constructed, wired, hardwired and hardwired! Just look at the titles of some of the popularizations:
Male and female brains wired differently, scans reveal
The hardwired difference between male and female brains could explain why men are 'better at map reading'
Male and Female Brains Really Are Built Differently
It’s true: male and female brains are wired differently. Study shows women’s brains are designed for social skills and memory, men’s for perception and co-ordination
The picture that reveals why men and women's brains really ARE different: The connections that mean girls are made for multi-tasking
Men and women's brains are 'wired differently' Men and women's brains are connected in different ways which may explain why the sexes excel at certain tasks, say researchers.
The fault for concluding something from the study which it cannot actually prove (that the observed differences in brain structure are "hardwired") lies firmly in the researchers' lap. The study uses the words "designed" and "wired" a lot:
Overall, the results suggest that male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes.
And
This, despite the fact that the study used data from young individuals (between ages eight and twenty-two), divided them into three age groups, to roughly match with childhood, teenage years and early adulthood, and then found the differences develop predominantly only after the age thirteen.
Now, it is quite possible that such a wake-up point could be consistent with a "hard-wired" explanation because puberty could switch on the process. But note that alternative explanations are possible: The way boys and girls interact with the world and the way the world interacts with them also changes when they hit puberty. Thus, to simply rule out anything to do with the way the genders use their brains (the trodden-paths explanation) looks to me unscientific, even somewhat biased. This is especially so because the case for innateness in the differences would have been much stronger if they had been visible from age eight onwards.
What did we get here? The researchers assert that their findings prove to be caused by structural engineering (which women don't now have to be pushed into, as several commentators gleefully asserted in the comments threads because girlz can't do math) without proving that. Then the popularizers go with that! Joy everywhere! Controversial topic! Lotsa clicks for advertisers, lotsa readers! Sex stereotypes are twue, as the study researcher Ragini Verma told in interviews! And I certainly had trouble understanding her (what with my frilly girl brainz) here:
Why does she want to go to a chef? And are hairstylists mainly men? I doubt that in the US. But never mind, we are told wonderfully controversial stuff, imputed to a picture of boy and girl brainz where the boys have blue brainz and the girls have orange brainz (which should be pink but the orange works, too).
Third, the whole research is about connectivity between parts of the brain, so it's apt to note that the paper makes poor connections between behavioral data on gender differences and the differences found in the structure of the brains. I quote from the article itself:
So from a larger study (with extra people with no brain scans added?), we learn that the behavioral differences which the imaging study argues it finds in everyone over the age 13 or so, are in reality mainly observed in midadolescent age (12-14 years)???
Cordelia Fine has written about this study today. I'm going to borrow more from her in my more detailed discussion of the study (see footnote), but she is worth quoting here, too:
A second cup of bitter coffee, anyone, to go with those fried boy and girl brainz?
Fourth, it really is necessary to ask when studies of this type are dragged out into the public square and when they are utterly ignored. I bet you can guess the main reason!
For instance, another very similar study using data on 439 individuals between the ages twelve and thirty, published last July, was not popularized because its findings about sex differences were modest. The researchers of the present study mention that study, but argue that their larger sample size (n=949) allows them to find statistically significant sex differences when the previous study could not do so (quote from the study);
The top two views are of a male brain, the bottom two views of a female brain. Those squiggly blue and orange lines are the increased connectivity paths. Men are from Mars, after all!
But WHOSE are these brains? Are these some kind of averages, constructed over the whole sample of 949 individuals? Or are they actual brains of two individuals? Neuro-scientists may know all about how such pictures are selected, but, alas and alack, I have no idea. And the article doesn't tell us. The answer to this question matters enormously, because it is these pictures readers seem to be reacting to. So we need to know how they were created and what they mean.
And here's the fun bit about those brain pictures: They are taken from the same Figure 2 in the article. Figure 2 also contains male and female comparison pictures for the three age groups in the study (children, teens and young adults), which to me sounds like all of the study, right? But those figures look a whole lot less dramatic:
Pictures B apply to children, pictures C to teenagers and pictures D to young adults. I assume that out of each pair of brains the female one is on the right. But the study doesn't tell us.
I am confused about the Now-Famous Pictures and these poor Cinderella pictures which weren't allowed to go to the public ball.
Nevermind. Have one more cup of coffee and look at this hilarious spoof version of the Now-Famous Pictures:
It's a very nice way of summarizing one of the main reason why this study has gotten so much publicity. The other reason would be in those fewer popularizations that suggested that men can never learn to multi-task (but see).
Fifth, and finally, a few important warnings: I'm obviously not an expert in neuro-science and what I discuss here is more based on my general knowledge how research should be reported as well as what more knowledgeable people (such as Dorothy Bishop, Tom Stafford, Cordelia Fine and Sophie Scott) report. Still, I'm fully responsible for all the things my feeble girl brain got wrong, even though that is sooo unfair.
Neither does anything I say imply that I believe there are no possible innate sex differences in the structure of the brain***. My point is that reporting inflated findings or links to behavior which the study itself cannot prove is not nice (files nails). Moreover it's bloody fu..ing deplorable when its consequences might be increased stereotype threats for women (and men), reduced advancement of women in fields where an individual woman is perfectly skilled for the job, but where prejudices about what women can do have been made stronger by bad research (and thus keep her from getting a job she applies for) and a discouraging belief that men simply cannot learn social skills or have good memory and so on.
And if you care to spend few hours tearing out your hair, do go and read what the comments threads to those popularizations talk about! The vast majority of them are about everybody knowing that women are like that and how the time now is ripe for feminazis to stop pushing women into the STEM fields and how all possible environmental effects on gender differences have now been proven false. Because of pictures of brainz! Which are colored blue for boys and orange for girls!
A few words about prior beliefs and prejudices: It looks to me as if those who commented on the popularizations of the Ingalhalikar et al. study were of three major types, ranked in rapidly reducing group size from the largest to the smallest: Many men (based on names or context) and a few women who loved the idea that women and men have now presumably been shown to be so fundamentally different that no further conversation can exist on anything having to do with gender differences, people (mostly women, I suspect) who were very angry at the study (and frightened by the way it is already used) and wanted to prove it wrong or have it proven wrong (which, anyway, is really impossible to achieve the same day a study comes out) and then quite a small group of people who talked about plasticity vs. hard-wiredness and some of whom actually were in neuroscience.
Taken together, these results reveal fundamental sex differences in the structural architecture of the human brain. Male brains during development are structured to facilitate within- lobe and within-hemisphere connectivity, with networks that are transitive, modular, and discrete, whereas female brains have greater interhemispheric connectivity and greater cross-hemispheric participation.
Bolds are mine.
This, despite the fact that the study used data from young individuals (between ages eight and twenty-two), divided them into three age groups, to roughly match with childhood, teenage years and early adulthood, and then found the differences develop predominantly only after the age thirteen.
Now, it is quite possible that such a wake-up point could be consistent with a "hard-wired" explanation because puberty could switch on the process. But note that alternative explanations are possible: The way boys and girls interact with the world and the way the world interacts with them also changes when they hit puberty. Thus, to simply rule out anything to do with the way the genders use their brains (the trodden-paths explanation) looks to me unscientific, even somewhat biased. This is especially so because the case for innateness in the differences would have been much stronger if they had been visible from age eight onwards.
What did we get here? The researchers assert that their findings prove to be caused by structural engineering (which women don't now have to be pushed into, as several commentators gleefully asserted in the comments threads because girlz can't do math) without proving that. Then the popularizers go with that! Joy everywhere! Controversial topic! Lotsa clicks for advertisers, lotsa readers! Sex stereotypes are twue, as the study researcher Ragini Verma told in interviews! And I certainly had trouble understanding her (what with my frilly girl brainz) here:
Ragini Verma, a researcher at the University of Pennsylvania, said the greatest surprise was how much the findings supported old stereotypes, with men’s brains apparently wired more for perception and coordinated actions, and women’s for social skills and memory, making them better equipped for multitasking.
“If you look at functional studies, the left of the brain is more for logical thinking, the right of the brain is for more intuitive thinking. So if there’s a task that involves doing both of those things, it would seem that women are hardwired to do those better,” she said.
“Women are better at intuitive thinking. Women are better at remembering things. When you talk, women are more emotionally involved - they will listen more.”
She added: “I was surprised that it matched a lot of the stereotypes that we think we have in our heads. If I wanted to go to a chef or a hairstylist, they are mainly men.”
Why does she want to go to a chef? And are hairstylists mainly men? I doubt that in the US. But never mind, we are told wonderfully controversial stuff, imputed to a picture of boy and girl brainz where the boys have blue brainz and the girls have orange brainz (which should be pink but the orange works, too).
Third, the whole research is about connectivity between parts of the brain, so it's apt to note that the paper makes poor connections between behavioral data on gender differences and the differences found in the structure of the brains. I quote from the article itself:
A behavioral study on the entire sample, of which this imaging study is a sub-set, demonstrated pronounced sex differences, with the females outperforming males on attention, word and face memory, and social cognition tests and males performing better on spatial processing and motor and sensorimotor speed (2). These differences were mainly observed in midadolescent age (12–14 y), where males performed significantly faster on motor tasks and more accurately on spatial memory tasks.
So from a larger study (with extra people with no brain scans added?), we learn that the behavioral differences which the imaging study argues it finds in everyone over the age 13 or so, are in reality mainly observed in midadolescent age (12-14 years)???
Cordelia Fine has written about this study today. I'm going to borrow more from her in my more detailed discussion of the study (see footnote), but she is worth quoting here, too:
In an larger earlier study (from which the participants of the PNAS study were a subset), the same research team compellingly demonstrated that the sex differences in the psychological skills they measured – executive control, memory, reasoning, spatial processing, sensorimotor skills, and social cognition – are almost all trivially small.
To give a sense of the huge overlap in behaviour between males and females, of the twenty-six possible comparisons, eleven sex differences were either non-existent, or so small that if you were to select a boy and girl at random and compare their scores on a task, the “right” sex would be superior less than 53% of the time.
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.
As for map-reading and remembering conversations, these weren’t measured at all.
Yet the authors describe these differences as “pronounced” and as reflecting “behavioural complementarity” – scientific jargon-speak for “men are from Mars, women are from Venus”. Rather than drawing on their impressively rich data-set to empirically test questions about how brain connectivity characteristics relate to behaviour, the authors instead offer untested stereotype-based speculation. Even though, with such considerable overlap in male/female distributions, biological sex is a dismal guide to psychological ability.
Also missing from the study is any mention of experience-dependent brain plasticity. Why?Bolds are mine.
A second cup of bitter coffee, anyone, to go with those fried boy and girl brainz?
Fourth, it really is necessary to ask when studies of this type are dragged out into the public square and when they are utterly ignored. I bet you can guess the main reason!
For instance, another very similar study using data on 439 individuals between the ages twelve and thirty, published last July, was not popularized because its findings about sex differences were modest. The researchers of the present study mention that study, but argue that their larger sample size (n=949) allows them to find statistically significant sex differences when the previous study could not do so (quote from the study);
Insignificant differences between the genders were observed in a recent study on SCs of 439 subjects ranging in age from 12–30 y (38). However, detailed analysis on a very large sample is needed to elucidate sex differences in networks reliably, as is provided in this study.
Dorothy Bishop notes, in her criticisms of the study that:
Indeed, she links to a post where Gerard Ridgway tries to figure** out the effect sizes which the Ingalhalikar et al. study doesn't tell us at all. Here's his picture of the effect sizes. The top graph (on sex differences in height) is to give you a comparison base for evaluating the effect sizes in the Ingalhalikar et al. study finding:
Hmm. It doesn't look quite so dramatic as one popularization led us to expect. The male and female distributions differ much less than they do for human height, even for the largest difference Ingalhalikar et al. found.
The point, my dear readers, is that the study was pushed as one about hard-wiredness, as one which reinforces old gender stereotypes and as one which finds humongous differences. Then the readers were given a script of interpreting those, not based on the images of the brains themselves but on the researchers' ideas about how men and women differ in behavior.
What really, really helped them to get this study out into the public arena wasn't just that it allowed wonderful comments threads where hundreds (if not thousands) mentioned that they knew all this already, that every man knows women cannot drive, that we should perhaps now let Larry Summers to run the Fed as we have proven that women can't do mathematics and that we should certainly stop pushing women into STEM careers which they don't want and cannot do.
It was also the pictures of the brainz. Bishop writes about another study:
Bolds are mine. A picture of a brain makes people suspend normal judgement? I think she's got something there!
Here is the picture most of the popularizations used. It's from the article itself (Figure 2) but looks to me to have been color-enhanced.
...if an effect was only evident when N = 900, then it would be a very small effect; in other words, while there may be a mean difference between males and females, the variation within each of those groups would be much larger than any difference between them. This was not conveyed at all in the media coverage.
Indeed, she links to a post where Gerard Ridgway tries to figure** out the effect sizes which the Ingalhalikar et al. study doesn't tell us at all. Here's his picture of the effect sizes. The top graph (on sex differences in height) is to give you a comparison base for evaluating the effect sizes in the Ingalhalikar et al. study finding:
Hmm. It doesn't look quite so dramatic as one popularization led us to expect. The male and female distributions differ much less than they do for human height, even for the largest difference Ingalhalikar et al. found.
The point, my dear readers, is that the study was pushed as one about hard-wiredness, as one which reinforces old gender stereotypes and as one which finds humongous differences. Then the readers were given a script of interpreting those, not based on the images of the brains themselves but on the researchers' ideas about how men and women differ in behavior.
What really, really helped them to get this study out into the public arena wasn't just that it allowed wonderful comments threads where hundreds (if not thousands) mentioned that they knew all this already, that every man knows women cannot drive, that we should perhaps now let Larry Summers to run the Fed as we have proven that women can't do mathematics and that we should certainly stop pushing women into STEM careers which they don't want and cannot do.
It was also the pictures of the brainz. Bishop writes about another study:
How is it that this paper has been so influential? I suggest that it is largely because of the image below, summarising results from the study. This was reproduced in a review paper by the senior author that appeared in Science in 2009. This has already had 42 citations. The image is so compelling that it’s also been used in promotional material for a commercial training program other than the one that was used in the study. As McCabe and Castel (2008) have noted, a picture of a brain seems to make people suspend normal judgement.
Bolds are mine. A picture of a brain makes people suspend normal judgement? I think she's got something there!
Here is the picture most of the popularizations used. It's from the article itself (Figure 2) but looks to me to have been color-enhanced.
The top two views are of a male brain, the bottom two views of a female brain. Those squiggly blue and orange lines are the increased connectivity paths. Men are from Mars, after all!
But WHOSE are these brains? Are these some kind of averages, constructed over the whole sample of 949 individuals? Or are they actual brains of two individuals? Neuro-scientists may know all about how such pictures are selected, but, alas and alack, I have no idea. And the article doesn't tell us. The answer to this question matters enormously, because it is these pictures readers seem to be reacting to. So we need to know how they were created and what they mean.
And here's the fun bit about those brain pictures: They are taken from the same Figure 2 in the article. Figure 2 also contains male and female comparison pictures for the three age groups in the study (children, teens and young adults), which to me sounds like all of the study, right? But those figures look a whole lot less dramatic:
Pictures B apply to children, pictures C to teenagers and pictures D to young adults. I assume that out of each pair of brains the female one is on the right. But the study doesn't tell us.
I am confused about the Now-Famous Pictures and these poor Cinderella pictures which weren't allowed to go to the public ball.
Nevermind. Have one more cup of coffee and look at this hilarious spoof version of the Now-Famous Pictures:
Fifth, and finally, a few important warnings: I'm obviously not an expert in neuro-science and what I discuss here is more based on my general knowledge how research should be reported as well as what more knowledgeable people (such as Dorothy Bishop, Tom Stafford, Cordelia Fine and Sophie Scott) report. Still, I'm fully responsible for all the things my feeble girl brain got wrong, even though that is sooo unfair.
Neither does anything I say imply that I believe there are no possible innate sex differences in the structure of the brain***. My point is that reporting inflated findings or links to behavior which the study itself cannot prove is not nice (files nails). Moreover it's bloody fu..ing deplorable when its consequences might be increased stereotype threats for women (and men), reduced advancement of women in fields where an individual woman is perfectly skilled for the job, but where prejudices about what women can do have been made stronger by bad research (and thus keep her from getting a job she applies for) and a discouraging belief that men simply cannot learn social skills or have good memory and so on.
And if you care to spend few hours tearing out your hair, do go and read what the comments threads to those popularizations talk about! The vast majority of them are about everybody knowing that women are like that and how the time now is ripe for feminazis to stop pushing women into the STEM fields and how all possible environmental effects on gender differences have now been proven false. Because of pictures of brainz! Which are colored blue for boys and orange for girls!
A few words about prior beliefs and prejudices: It looks to me as if those who commented on the popularizations of the Ingalhalikar et al. study were of three major types, ranked in rapidly reducing group size from the largest to the smallest: Many men (based on names or context) and a few women who loved the idea that women and men have now presumably been shown to be so fundamentally different that no further conversation can exist on anything having to do with gender differences, people (mostly women, I suspect) who were very angry at the study (and frightened by the way it is already used) and wanted to prove it wrong or have it proven wrong (which, anyway, is really impossible to achieve the same day a study comes out) and then quite a small group of people who talked about plasticity vs. hard-wiredness and some of whom actually were in neuroscience.
All those people most likely have a prior belief about how much and in which ways women and men might innately differ, and it is those prior beliefs that even researchers have. In that sense all these discussions will be gender-political, between those who think that men are from Mars and women are from Venus and between those who think that all such prior beliefs are pulled from Uranus.
The gender-political aspect has much to do with power and struggles for higher positions in the society, vs. trying to stay on top of the heap, and it has also much to do with feeling that one deserves, in a natural way, the good things one has or the feeling that others are out to get you either for being the oppressor or by making sure that you remain the oppressed. It's all very emotional! In a gender-neutral way, my friends.
The gender-political aspect has much to do with power and struggles for higher positions in the society, vs. trying to stay on top of the heap, and it has also much to do with feeling that one deserves, in a natural way, the good things one has or the feeling that others are out to get you either for being the oppressor or by making sure that you remain the oppressed. It's all very emotional! In a gender-neutral way, my friends.
These are the reasons why studies on gender differences should measure twice and cut once, as carpenters say. Researchers' mistakes heap very high social costs on the shoulders of others, much higher than is in general the case with published research. And that is the reason why I spend so much time on studies of this type and why I always try to bite the butts of bad popularizations.
These things matter.
On my own biases: You can tell what they might be when my first quick reading of the study made me mutter how exaggerated it sounded. That is a bias, too, of course, with a real world basis: I don't see the kind of gendered differences in behavior which would suggest large fundamental differences in the architecture of the brain. I do see differences, sure, but with lots and lots of individual variation and much weaker general differences than the Ingalhalikar et al. tells us it has established, and I cannot really tell, for most of them, what the environmental effect in them might be. And they say zero about individual variation, they fail to provide effect sizes. These are the kinds of things which turn my skepticism engines on.
Whatever that is worth. You can take any leftovers home with you if so desired. A few additional criticisms about the study are left in the footnote if you are still peckish.****
--------------------------------
*The paper can be found and purchased here. Ruben and Raquel Gur, among the authors of the paper, have been studying gender differences for thirty years. They and Regini Verma wrote the actual paper, which suggests to me that they chose to talk about hard-wiring and so on.
**I have not tried to check any of the calculations, either here or in Ingalhalikar et al..
***In any case, the proof of the pudding is in the eating. As both birds and bats can fly, so it is possible that brainz with quite different paths can solve the same problems and accomplish the same tasks. For several examples of recent studies which have found sex differences in structural imaging (but not necessarily in the same direction or in the same places) read here, here, here and here.
For some criticisms of this field, check out this.It includes a fascinating quote pertinent to this topic:
For some criticisms of this field, check out this.It includes a fascinating quote pertinent to this topic:
Of course, sex differences are also found at cellular and molecular levels of the central nervous system (Cosgrove et al., 2007). But whether it involves gene expression, neuronal signaling, gross structure, or regional blood flow, every brain-related sex difference is not necessarily behaviorally relevant. As Geert De Vries (2004) has shown, sex differences in neural circuitry or neurochemistry often reflect compensation for genetic and hormonal differences and actually end up making male and female behavior more similar than different.
****The two more technical criticisms I have seen have to do with brain size and head motion. Those might look very weird, for the uninitiated, but they both matter here, because men have, on average, larger brains, than women, and because one study found that the amount of head motion in young male subjects during imaging was clearly somewhat higher than the amount of head motion in young female subjects and it confounded some of the results of the imaging.
On the size of the brain, Fine states:
One important possibility the authors don’t consider is that their results have more to do with brain size than brain sex. Male brains are, on average, larger than females and a large brain is not simply a smaller brain scaled up.I came across the same suggestion in other literature and also some findings that the imaging results may suffer if there is a consistent brain size difference between groups. Some conclusions may be caused by that rather than whatever the study tries to analyze. To test this, one might try to compare large-brained women with smaller-brained men? I have no idea if that is doable.
Larger brains create different sorts of engineering problems and so – to minimise energy demands, wiring costs, and communication times – there may physical reasons for different arrangements in differently sized brains. The results may reflect the different wiring solutions of larger versus smaller brains, rather than sex differences per se.
On the head motions: This study (Figure1) shows a sex difference in the amount of head motion during the imaging. Head motion is greater for males than for females. Moreover, the effect of greater average head motion was found to be associated with apparent decreased functional connectivity in large-scale networks and apparent increased functional connectivity between the left and right motor regions. As far as I can figure out, that is exactly what one would expect in the Ingalhalikar et al. study which seems not to have taken head motion into account at all. At the same time the authors of the article studying the effect of head motion find its impact to fairly small on the results in their study. On the other hand, they state:
Paradoxically, large data samples may be particularly vulnerable to this kind of confound where small, systematic differences in motion could become the dominant difference as other sources of variation are matched between groups. The rightmost panel of Figure 4 illustrates this point. The panel compares two large samples (each n = 100) that were matched for age and sex but systematically differed in a small degree of motion (0.044 versus 0.048 mm Mean Motion displacement). A between-group effect on functional connectivity of the default network is evident that is most likely entirely driven by head motion. This difference in another context could easily be mistaken for a true neuronal effect.
Given this, the Ingalhalikar et al. study should be