Katarack21 Posted May 29, 2018 Share Posted May 29, 2018 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3110817/ Ooh, you linked some literature! Let's take a a look at it. This is from the abstract (incidentally, right after your quotation, which is missing actual quotes or any other indicator of citation, cuts off): While we revealed significant main effects of sex, there were no significant effects of brain size (and no significant interactions between sex and brain size). Huh. That doesn't seem to mesh with what you're saying. But it gets better. When conducting post hoc tests, we revealed a number of regions where women had larger GM volumes compared to men. Importantly, these sex effects remained evident when comparing men and women with the same brain size. Altogether, our findings suggest that the observed increased regional GM volumes in female brains constitute sex-dependent redistributions of tissue volume, rather than individual adjustments attributable to brain size. Golly. That's specifically important because it establishes that you cannot characterize gray matter as masculine or white matter as feminine - the two have different configurations and connotations in ways that both are and are not sex-dependent. Now of course, that on its own speaks to the statistical differences between men's brains and women's brains, so I'll link this again: while the grey-to-white matter ratios differ observably between the sexes, the actual significance of those differences is not well established, as women with less grey matter perform equivalently to men with more grey matter on identical tests. But of course, even if you didn't take a look at the article in question, you should already know about its contents, because this ... https://www.sciencedaily.com/releases/2005/01/050121100142.htm ... is actually about the article I just linked. It's a pretty good summary! Here's the handy tidbits you didn't include in your post. The study shows women having more white matter and men more gray matter related to intellectual skill, revealing that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance. “These findings suggest that human evolution has created two different types of brains designed for equally intelligent behavior,” said Richard Haier, professor of psychology in the Department of Pediatrics and longtime human intelligence researcher, who led the study with colleagues at UCI and the University of New Mexico. “In addition, by pinpointing these gender-based intelligence areas, the study has the potential to aid research on dementia and other cognitive-impairment diseases in the brain.” The study also identified regional differences with intelligence. For example, 84 percent of gray-matter regions and 86 percent of white-matter regions involved with intellectual performance in women were found in the brain’s frontal lobes, compared to 45 percent and zero percent for males, respectively. The gray matter driving male intellectual performance is distributed throughout more of the brain. According to the researchers, this more centralized intelligence processing in women is consistent with clinical findings that frontal brain injuries can be more detrimental to cognitive performance in women than men. Studies such as these, Haier and Jung add, someday may help lead to earlier diagnoses of brain disorders in males and females, as well as more effective and precise treatment protocols to address damage to particular regions in the brain. Interesting stuff! The article's full text can be found here. But, as we'll see, this is greatly recontextualized by later research. See, the studies we've looked at so far are methodologically sound but also older and limited in scope - the Ludders study (from 2011) looked at a sample size of 96 brains, while the Haier article looked at 48 volunteers. These are actually pretty large samples as far as neuroscience goes, and I wouldn't want to imply that these small samples indicate unreliability. But what they definitively establish is that the brain does diverge, statistically, along rough male and female lines. This seems like a good place for me to relink this study, from 2015, which looks at a sample size of 1,400 brains (you can't see me, but I'm fanning myself and feeling faint now), and builds on the Haier and Ludders work towards the conclusion that - rather than earlier notions of male brains vs female brains, or of brains appearing on a linear male-to-female continuum - the average person's brain is a "mosaic" of features, some of which are more common in men, some of which are more common in women, and some of which have no statistical correlation with sex. They also did a psychological study of 5,500 individuals (holy logistics, Batman!), with convergent results. But it gets even weirder, as reality tends to do! ... more recent evidence that masculinization and feminization are independent processes and that sexual differentiation progresses independently in different brain tissues (10), predicts poor internal consistency [of masculinization or feminization in the brain] (4, 5). Poor internal consistency is further predicted by evidence that the effects of sex may be different and even opposite under different environmental conditions and that these sex-by-environment interactions may be different for different brain features (4, 5). Emphasis mine. (I'm really enthusiastic about that bit in particular because it's totally new to me - I learned it while researching my post yesterday, and I wish I could have fit it in. Thank you for giving me the opportunity to!) So, let me see if I can sum this all up. A handy-dandy list may be useful. Per a 2005 article by RJ Haier, based on a sample size of 48, different distributions and ratios of white-to-grey matter are recognizable between male and female volunteers, but appear to produce equivalent general intelligence results. Per a 20011 article by E Ludder, based on a sample size of 96, sex differences between brains are structural, not linear, and cannot be explained away with "men sometimes have larger brains," or "men have more grey matter." Per a 2015 article by D Joel, based on a sample size of 1,400 MRIs, the appearance of masculine and feminine features of the brain is not linear and only predictable in the broadest statistical terms: any given person's brain is a totally unpredictable sampling of features that are typically masculine, typically feminine, or typically unassociated with sex. It also appears that environmental factors can sometimes reverse what is statistically masculine or feminine. I wish I could click like on this post twenty times. It's *beautiful*. I'd also like to point out that I linked to the study about the "mosaic" nature of brains earlier in this thread. :-D 1 Link to comment Share on other sites More sharing options...
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