Sex-associated neuroanatomical and behavioral differences based on scientific evidence. Why were these differences shelved?
In its leveling and egalitarian zeal, the fastidious social and political correctness gradually being instated in recent years threatens not only freedom of expression, but even the scientific evidence. A matter as obvious as the differences between sexes is now interpreted in some fields as a cultural imposition of already outdated traditions, not as a biological condition. Sex, therefore, is not determined by nature but is a mental state, malleable and alterable based on powerful feelings or disturbing sensations.
Some physiological differences
Logically, those differences do not affect the equal dignity of genders, but they do affect muscles and sporting brands, reproductive complementarity, artistic sensitivity, television interests, processing of emotions, and even ways of falling ill: females suffer from more Alzheimer’s disease, their heart attacks are more serious and complicated, their immune system makes them more susceptible to certain allergic diseases, and their colon tumors are located in different places than in men.
Sex-associated neuroanatomical and behavioral differences
In the latest edition of the journal Stanford Medicine, Bruce Goldman remembers the controversy caused in the 1990s by the book Sex Differences in Cognitive Abilities, by Diane Halpern (see the book available on its 4th Edition), then president of the American Psychological Association and today professor emeritus at Claremont McKenna College. Halpern, contrary to what was thought, discovered that studies in animals kept reporting sex-associated neuroanatomical and behavioral differences, but these observations were immediately shelved, since they did not agree with the wishes of the leading psychologists and sociologists. “There was too much data pointing to the biological basis of sex-based cognitive differences to ignore […] 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.
More recent study in boys and girls
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.”
The egalitarian and asexual scientists describe colleagues who assure that the biological and cerebral differences between sexes contribute to disparities in behavior and cognition as “neurosexist”.
Halpern lists some of these differences:
- on average, women excel in verbal ability,
- reading comprehension and writing ability, and they outperform men in tests of fine-motor coordination, l
- long-term memory and perceptual speed;
- men, for their part, have better working memory and visuospatial skills, such as tracking moving objects and aiming.
Many of these cognitive differences appear very early in life. “You see sex differences in spatial-visualization ability in 2- and 3-month-old infants,” Halpern says. “Infant girls respond more readily to faces and begin talking earlier. Boys react earlier in infancy to experimentally induced perceptual discrepancies in their visual environment. In adulthood, women remain more oriented to faces, men to things.”
Different incidence of cognitive and neuropsychiatric disorders
The long list of behavioral tendencies in which male-female ratios are unbalanced extends to cognitive and neuropsychiatric disorders. Women are twice as likely to experience clinical depression and post-traumatic stress disorder; and men are twice as likely to become alcoholic or drug-dependent, are 40 percent more likely to develop schizophrenia, boys’ dyslexia rate is 10 times that of girls, and they are four or five times as likely to get a diagnosis of autism spectrum disorder.
Differences extend well beyond the strictly reproductive domain
“The neuroscience literature shows that the human brain is a sex-typed organ with distinct anatomical differences in neural structures and accompanying physiological differences in function,” says Larry Cahill, professor of neurobiology and behavior at the University of California – Irvine. Cahill edited a special edition of the Journal of Neuroscience Research, published in January this year, devoted to the influence of sex differences on nervous-system function. Brain-imaging studies indicate that these differences extend well beyond the strictly reproductive domain, explains Cahill. Thus, a woman’s hippocampus, critical to learning and memorization, is larger than a man’s and works differently. Conversely, a man’s amygdala, associated with the experiencing of emotions and the recollection of such experiences, is bigger than a woman’s, and it too works differently, as Cahill’s research has demonstrated.
Women are known to retain stronger, more vivid memories of emotional events than men. The two hemispheres of a woman’s brain talk to each other more than a man’s, according to a 2014 study by University of Pennsylvania researchers, published in the Proceedings of the National Academy of Sciences. The authors imaged the brains of 428 male and 521 female youths: the females’ brains consistently showed more strongly coordinated activity between hemispheres, while the males’ brain activity was more tightly coordinated within local brain regions. The study confirmed that the corpus callosum — the white matter that connects the hemispheres — is bigger in women, whose brains tend to be more bilaterally symmetrical. To some extent, “these brain differences have to translate to behavioral differences”, surmises Cahill.
The specific hormones of each sex would act not only on the reproductive organs, but also on the brains, not to mention the XX and XY chromosome configuration. As Nirao Shah, a neurobiologist at Stanford University in California (see the large neurologic study HERE), asks: If the presence or absence of a single DNA base pair can lead to a genetic disorder, how can we disregard the effect of a chromosome? Just last month, a team from the Weizmann Institute in Israel published an article in BMC Biology (see HERE our Special Report about this issue), in which they identified 6,500 genes expressed differently in men and women after scanning 500 genomes in the GTEx project: from skin hair to muscle fibers to fat cells.
José Ramón Zárate. (Diario Médico)