Stark, Undeniable Differences in the Brains of Men and Women

Perhaps twenty or thirty years ago an educated person might have been excused for denying any differences in structure and function between the brains of human males and human females. But things have changed.

… over the past 15 years or so, there’s been a sea change as new technologies have generated a growing pile of evidence that there are inherent differences in how men’s and women’s brains are wired and how they work. __ Neurobiologist Nirao Shah

SEX ON THE BRAIN: A mammalian embryo is female by default. Males develop when the Sry gene of the Y chromosome is expressed, spurring the development of testes. During fetal development, the testes produce large amounts of testosterone, much of which is converted to estrogen. Both hormones then act on the brain, inducing the cellular process of masculinization.

If not for the Y chromosome gene Sry, no embryonic testicles would be produced. If not for embryonic testicles and their large-scale production of testosterone, no males — and no male brains — would be produced.

Many sex differences in adult brain structure and behaviors are the result of in utero organizational effects of gonadal steroid hormones, in particular androgens and their aromatized derivatives, estrogens, both of which are present in substantially higher concentrations in male fetuses due to testicular steroidogenesis. Brain differences between the sexes can also arise from diverse factors, including the expression of genes carried on the sex chromosomes and discrepancies in maternal treatment of male and female progeny. Together, these factors mediate differences in neurogenesis, myelination, synaptic pruning, dendritic branching, axonal growth, apoptosis, and other neuronal parameters. __ Neuroscientist Margaret McCarthy in The Scientist

Neuroscientists have been homing in on brain differences between men and women for many decades. Thanks to better tools for brain imaging and genetic analysis, our understanding of these stark sex differences is growing clearer and more detailed.

Sex differences in lower animals often reflect sex differences in humans, providing a clue that a large part of human sex differences in brain and behaviour have been programmed in by long periods of evolution.

… animal-research findings resonated with sex-based differences ascribed to people. These findings continue to accrue. In a study of 34 rhesus monkeys, for example, males strongly preferred toys with wheels over plush toys, whereas females found plush toys likable. It would be tough to argue that the monkeys’ parents bought them sex-typed toys or that simian society encourages its male offspring to play more with trucks. A much more recent study established that boys and girls 9 to 17 months old — an age when children show few if any signs of recognizing either their own or other children’s sex — nonetheless show marked differences in their preference for stereotypically male versus stereotypically female toys.

… “These findings have all been replicated,”… Women excel in several measures of verbal ability — pretty much all of them, except for verbal analogies. Women’s reading comprehension and writing ability consistently exceed that of men, on average. They out­perform men in tests of fine-motor coordination and perceptual speed. They’re more adept at retrieving information from long-term memory.

Men, on average, can more easily juggle items in working memory. They have superior visuospatial skills: They’re better at visualizing what happens when a complicated two- or three-dimensional shape is rotated in space, at correctly determining angles from the horizontal, at tracking moving objects and at aiming projectiles. __ Stanford Medicine

A large meta-analysis of brain volumetric studies recently established that there are significant sex differences in the volumes of various compartments of the brain.

On average, males have larger total brain volumes than females. Examination of the breakdown of studies providing total volumes by age categories indicated a bias towards the 18–59 year-old category. Regional sex differences in volume and tissue density include the amygdala, hippocampus and insula, areas known to be implicated in sex-biased neuropsychiatric conditions.

… On average, males have larger grey matter volume in bilateral amygdalae, hippocampi, anterior parahippocampal gyri, posterior cingulate gyri, precuneus, putamen and temporal poles, areas in the left posterior and anterior cingulate gyri, and areas in the cerebellum bilateral VIIb, VIIIa and Crus I lobes, left VI and right Crus II lobes. Females on average have larger volume at the right frontal pole, inferior and middle frontal gyri, pars triangularis, planum temporale/parietal operculum, anterior cingulate gyrus, insular cortex, and Heschl’s gyrus; bilateral thalami and precuneus; the left parahippocampal gyrus and lateral occipital cortex (superior division). __

These results can only be considered preliminary, although they came from a large set of compiled data from 126 detailed scientific studies of male and female brain and brain compartment volumes.

Human Males and Females Have Complementary Brain Talents

The study below used brain tensor imaging to look at the brains of 428 young human males and 521 young human females.

Sex differences are of enduring scientific and societal interest because of their prominence in the behavior of humans and nonhuman species (1). Behavioral differences may stem from complementary roles in procreation and social structure; examples include enhanced motor and spatial skills and greater proclivity for physical aggression in males and enhanced verbally mediated memory and social cognition in females (2, 3). With the advent of neuroimaging, multiple studies have found sex differences in the brain (4) that could underlie the behavioral differences. Males have larger crania, proportionate to their larger body size, and a higher percentage of white matter (WM), which contains myelinated axonal fibers, and cerebrospinal fluid (5), whereas women demonstrate a higher percentage of gray matter after correcting for intracranial volume effect (6). Sex differences in the relative size and shape of specific brain structures have also been reported (7), including the hippocampus, amygdala (8, 9), and corpus callosum (CC) (10). Furthermore, developmental differences in tissue growth suggest that there is an anatomical sex difference during maturation (11, 12), although links to observed behavioral differences have not been established.

The study revealed fundamental sex differences in brain structural architectures of young human males and females. Such structural differences will need to be correlated with behavioural differences — such as the differences in choices of occupations which have proven to be so troubling to feminist academics and policy-makers.

Larger Study in Brains of Grown Men and Women Reveals More Sex Differences

In the new study, a team of researchers led by psychologist Stuart Ritchie, a postdoctoral fellow at the University of Edinburgh, turned to data from UK Biobank, an ongoing, long-term biomedical study of people living in the United Kingdom with 500,000 enrollees. A subset of those enrolled in the study underwent brain scans using MRI. In 2750 women and 2466 men aged 44–77, Ritchie and his colleagues examined the volumes of 68 regions within the brain, as well as the thickness of the cerebral cortex, the brain’s wrinkly outer layer thought to be important in consciousness, language, memory, perception, and other functions.

Adjusting for age, on average, they found that women tended to have significantly thicker cortices than men. Thicker cortices have been associated with higher scores on a variety of cognitive and general intelligence tests. Meanwhile, men had higher brain volumes than women in every subcortical region they looked at, including the hippocampus (which plays broad roles in memory and spatial awareness), the amygdala (emotions, memory, and decision-making), striatum (learning, inhibition, and reward-processing), and thalamus (processing and relaying sensory information to other parts of the brain).

When the researchers adjusted the numbers to look at the subcortical regions relative to overall brain size, the comparisons became much closer: There were only 14 regions where men had higher brain volume and 10 regions where women did. __ Sciencemag

The point is not that men have larger brains than women. The important thing is to look at specific brain regions where men’s brains seem more developed, and compare this with the specific brain regions where women’s brains seem more developed. Then you can move forward in the attempt to correlate brain developmental and functional differences with the abundant real-world behavioural differences between men and women.

A Closer Look at the Above Study

… performance on mental rotation tasks (Maeda and Yoon 2013) and physical aggression (Archer 2004) are on average higher in males, whereas self-reported interest in people versus things (Su et al. 2009) and the personality traits of neuroticism (Schmitt et al. 2008) and agreeableness (Costa et al. 2001) are on average higher in females. A full explanation of these cognitive and behavioral phenomena might benefit from a better understanding of brain sex differences.

… There is more to sex differences than averages: there are physical and psychological traits that tend to be more variable in males than females. The best-studied human phenotype in this context has been cognitive ability: almost universally, studies have found that males show greater variance in this trait (Deary et al. 2007a; Johnson et al. 2008; Lakin 2013; though see Iliescu et al. 2016). This has also been found for academic achievement test results (themselves a potential consequence of cognitive differences, which are known to predict later educational achievement; Deary et al. 2007b; Machin and Pekkarinen 2008; Lehre et al. 2009a, 2009b), other psychological characteristics such as personality (Borkenau et al. 2013), and a range of physical traits such as athletic performance (Olds et al. 2006), and both birth and adult weight (Lehre et al. 2009a). __ Cerebral Cortex Ritchie et al 2018

The greater variance in cognitive ability in males as compared to females is another source of concern for feminists in academia, politics, and in both governmental and non-governmental bureaucracies.

Men Dominate at the Highest Levels

Whether looking at the number of male vs. female CEOs of large corporations, leaders of governments, winners of Nobel Prizes and Fields Medals, top chefs, most skilled chess grandmasters, the best aircraft pilots, the most dominant athletes, top surgeons, best violinists, most successful entrepreneurs and venture capitalists, etc. etc. — males tend to outnumber females.

Charles Murray’s masterful book “Human Accomplishment” looked at the achievements of top mathematicians, scientists, artists, etc. between the years 800 BC and 1950 CE. Murray discovered that — just as in contemporary Nobel Prizes and Fields Medals — men vastly outnumber men when it comes to historical accomplishments.

Murray found that women consistently make different career choices than men, which divert them from the path of great achievement time after time.

The women with careers were 4.5 times as likely as men to say they preferred to work less than 40 hours a week. The men placed greater importance on “being successful in my line of work” and “inventing or creating something that will have an impact,” while the women found greater value in “having strong friendships,” “living close to parents and relatives” and “having a meaningful spiritual life.” As the authors concluded, “these men and women appear to have constructed satisfying and meaningful lives that took somewhat different forms.” The different forms, which directly influence the likelihood that men will dominate at the extreme levels of achievement, are consistent with a constellation of differences between men and women that have biological roots.

… Men take more risks, are more competitive and are more aggressive than women. The word testosterone may come to mind, and appropriately. Much technical literature documents the hormonal basis of personality differences that bear on sex differences in extreme and venturesome effort, and hence in extremes of accomplishment–and that bear as well on the male propensity to produce an overwhelming proportion of the world’s crime and approximately 100% of its wars.

But this is just one more of the ways in which science is demonstrating that men and women are really and truly different, a fact so obvious that only intellectuals could ever have thought otherwise. __ Charles Murray

And yet, both intellectuals and pseudo-intellectuals in positions of influence and power continue to force destructive policies on institutions such as universities, government agencies, corporations, and others — and are fully backed by the inferior intellectuals and pseudo-intellectuals who infest most mass media outlets.

In sports, a dominant female athlete such as Serena Williams would be lucky to reach a male rank of 700, in terms of tennis skill and endurance on the men’s circuit. Men play longer and harder games. In fact, Serena and her sister Venus were both soundly trounced by a smoking and beer-drinking german male tennis player years ago, when both women were stronger and faster.

…the two siblings had something of an inflated understanding of their abilities, developed from their being fresh-faced, and still in need of a few life lessons learned. So they marched themselves into the men’s ATP office to announce rather confidently they were ready to beat any tour player ranked around the Top 200 if someone wanted to take the challenge.

It just so happened that Karsten Braasch of Germany, once a top-40 player, but at the time ranked 203rd, was in ear shot. He thought it would be fun so stepped up to say he’d be happy to take them on.

The date was set and the day arrived. Braasch played a warmup round of golf in the morning, then came to Melbourne Park. The threesome went out to a back court where each sister would have a one-set shot at Braasch. Word had spread around the grounds that the event wsa taking place, which caused tournament officials to restrict admittance to the area to only those with badges.

Braasch would smoke cigarettes and sip beer during the changeovers, and to be honest no longer looked the part of a fit professional athlete. It made no matter. Braasch led 5-0 over Serena before winning the set 6-1, and then posted a 6-2 set victory over Venus.

Society cannot afford to live in a make-believe world where its best women are just as capable in all areas as its best men. It isn’t true, and it is a great waste of talent from both sexes to try to prove the egalitarian ideal.

84% of women fail watered down physical fitness test

And so we are faced with a world that needs the best of all of its talented people — male and female. But our bureaucratic planners and policy-makers refuse to allow our best people to do their best. Instead, these functionaries insist on quotas, mandates, affirmative actions, and a long list of other ruinously expensive and damaging regulations and policies that handicap us from doing our best.

In a large sample of mathematically gifted youths, for example, seven times as many males as females scored in the top percentile of the SAT mathematics test. We do not have good test data on the male-female ratio at the top one-hundredth or top one-thousandth of a percentile, where first-rate mathematicians are most likely to be found, but collateral evidence suggests that the male advantage there continues to increase, perhaps exponentially.  __  Charles Murray

A strong dose of reality at the highest levels is needed, but it is not clear who will do the dosing — and whether anyone in need of the dose will be capable of learning anything from it.

Hope for the best. Prepare for the worst. It is never too late to have a Dangerous Childhood © .

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6 Responses to Stark, Undeniable Differences in the Brains of Men and Women

  1. matthewpmusson says:

    I heard it summed up quite clearly when one neurologist stated:
    “The difference between male and female brains is at least as pronounced as the difference in height between males and females.”

    • alfin2101 says:

      The differences for brains are greater at the tails of the distributions. More geniuses, more morons.
      For height the difference is greater at the right hand tail. More giants.

  2. Luke says:

    “A mammalian embryo is female by default. ”
    I think it would more accurate for scientists to say that a mammalian embryo is undifferentiated by default. If it has the male chromosome, then it is male. A failure to express the male chromosome would be a disease state, not a default state. Saying that female is the default pretends that an embryo is not also defined by its own DNA, and comes across as a bit ignorant/obfuscating to me.

    • alfin2101 says:

      Everyone is welcome to an opinion — thanks for expressing yours. The author of the piece that you criticise, Margaret McCarthy, is a highly trained scientist, and she expressed her opinion that mammalian embryos are indeed female by default.

      The XO chromosomal disorder “Turner’s Syndrome” produces a female usually incapable of breeding without serious intervention by modern reproductive technologies. This illustrates the “default” state as nearly as possible.

      The Turner Syndrome child appears female at birth. Some TS women have reproduced successfully without intervention, but that is rare. Health problems are common.

      An embryo is not “defined” by its DNA, although it is strongly influenced by it. DNA is not a blueprint, it is a recipe that keeps cooking for the entire life of the organism.

  3. Atavisionary says:

    You should check out the book “Smart and Sexy” by roderick kaine. It goes into a lot of detail on this as well as the likelihood of X linked intelligence genes accounting for greater male variability.

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