I pointed out that that Daphna Joel’s work was crap – she was trying to find ways that can’t distinguish between male and female brains – that’s easy but useless. But if you can find one approach, any approach, that reliably distinguishes male and female brains, then they’re different. But even then, not necessarily different in ways that anyone could ever give a shit about. Or if they are, the approach that distinguishes male from female may not tell you much about the behavioral differences you’re interested in.
Important differences might not show up in brain scans. For example, we can’t see schizophrenia in a brain scan, yet schizophrenia is important. Hearing voices that aren’t there, even when they give useful tips [ “They’re all against you! They all must die!” ] has social significance. Sure, there are some differences between crazy and not-yet-crazy brains [shrunken ventricles], but they’re not huge and (with what we know today) they’re not diagnostic. Yet we have good reason to believe schizophrenia is caused by differences in the brain – we just can’t say exactly what they are. Even when we know the underlying genetic cause – which we do, in a few cases – we generally don’t know the details of how that genetic flaw changed brain development and/or activity.
You could have a psychological sex difference as drastic as schizophrenia and we likely couldn’t identify it from a brain scan. Not seeing it in a brain scan wouldn’t show that the psychological difference didn’t exist. Got it?
Narcolepsy, massive daytime sleepiness, is generally caused by loss of the neurons that secrete the neuropeptide orexin/hypocretin. Only 10,000-20,000 neurons do this, and I sincerely doubt if you could notice the difference via MRI or CAT scans if they all disappeared.
Inability to see the physical basis via scans is often [not always] the case with various kinds of brain damage or mental illness, but the neurological basis of behavioral adaptations is also usually unobservable via such scans. We don’t know how to detect the brain differences that make a border collie inclined to herd, or that cause the personality differences between a pit bull and a Labrador retriever.
What does this say to someone trying to show effective sameness of female and female psychology by showing effective sameness of male and brains? It can’t be done, with the tools we have. Just as well, since that conclusion [no differences] is almost certainly wrong, since natural selection routinely creates wired in behavioral differences between the sexes. It would be surprising if that kind of natural selection had taken an extended holiday in humans.