Mounting challenge to brain sex differences

I work in a area related to this: neural aging. Many of my collaborators are constantly looking for gender differences in the basal brain and WRT the aging process.<p>They are encouraged to do this by a semi-recent NIH policy strongly encouraging experiments to include both genders because of a perception that females were being left out of biological research. I don&#x27;t think that is true, because for example NCBI GEO samples are virtually equally balanced between M&#x2F;F, but hey, NIH has to play along with politics to some extent to get funding.<p>So once investigators have gone to the trouble and expense of including both genders in an experiment, they will naturally do the analysis comparing genders. They will perform lots of comparisons, sort the p-values, and declare some differences. And to provide a fig leaf for readers concerned that our time is being wasted, they will say these differences which are probably often statistical artifacts, are &quot;important&quot; for some nebulous, rarely explained reason.<p>This is not to say there are NO differences. In the context of aging, female humans live several years longer than males on average, and there are some biological reasons for that. It&#x27;s just that it beggars my imagination to think that core biological processes unrelated to reproduction would have vast differences between genders. Evolution, it should be remembered, predates gender by a long time. More importantly, if we are trying to understand core biology, we should be focusing on the main effect IMO rather than the relatively minor gender differences.

That article has some kind of hasty judgement, saying that because a tiny brain structure is equal in men and women it is evidence for the whole brain being the same...<p>Yet what about other obvious evidence of the differences, like the fact that men brains are usually obviously heavier? Or the differences in overall distribution of grey and white matter? or that many neurological disorders, like aspergers syndrome, have different symptoms depending on the sex?

I didn&#x27;t read the actual study, but from the article they are basing this on the amygdala size being bigger but the male brain also just overall being bigger.<p>My question is: What rules out the bigger size itself (irregardless of overall brain size) causing differences? Perhaps, the ratio of amygdala size to brain size does not matter but rather just the absolute size.

They are demonstrating that they didn&#x27;t find difference. Not that none exist. They do exist, and this is easy to verify with the Piaget Water Level Task.<p>The task is simple. Draw a cup like |_| and then the same tilted perhaps 30 degrees. Hand the pictures to someone and ask, &quot;If they are both half-full of water, draw the water line.&quot; Conduct this experiment on 5 random adult friends of each gender.<p>With extremely high probability, you will now have very strong evidence that there are very real brain sex differences. No demonstrated ones that seem particularly important to me, but clearly they exist.<p>(I first encountered this as part of a pair of questions, this one and another which women got and men didn&#x27;t. I thought it was BS, a month later gave this one to my then girlfriend, and have never again found the other. Incidentally there is no difference on performance in this one until puberty. Interestingly the odds of success for gay&#x2F;trans people are between straights, suggesting that their brains tend to be mixes of &quot;normal&quot; in more ways that one.)

I wonder what the transgender community has to say about this given their efforts to prove that there are differences.

TLDR; Evidence is piling up that the male brain &#x2F; female brain concept is nothing more than a myth.