Cognitive differences between sexes
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Differences in male and female cognitive abilities are widely established in the current scientific literature. What is still unclear is how much of these differences is due to biological and genetic differences between sexes, and how much is due to environment and culture.
These studies can lead to controversies very easily, mostly because of the following reasons:
- Scientific claims about sex differences in mental abilities are misunderstood as sexism. In truth, scientists do not say that one sex is more intelligent, hence superior, or more stupid, hence inferior, than the other. The studies focus on how, and how much, males and females think differently, and why it is so.
- Statistical results are misunderstood as general claims about men and women. If on average a sex performs better/worse in some cognitive task, this does not mean that all the people of such sex are better/worse in that task. Indeed, studies consistently have many exceptions, and the distributions of men's and women's cognitive abilities overlap a lot. So nothing can be said on the intelligence of a single person just by knowing their sex, but statistics can be used to understand general trends on the whole population of men and women.
- This topic attracts a lot of pseudoscience, anecdotal evidence, myths, and — in the worst case — dishonest people who try to bend the science in order to support their ideas on men and women.
Additionally, to make things more complicated, the brains of transgender people might be quite peculiar, since tensor imaging studies suggest that they present complex mixtures of masculine, feminine, and demasculinized, defeminized regions.
There are some differences between brain structures between the sexes. The brain, however, is a highly complex structure and is still being studied, so none of these, of course, should translate to higher intelligence or having desirable or undesirable behavior traits (after all, that would be grossly reductionist) nor is there conclusive evidence of the extent these structures can be changed by socialization, cultural upbringing, and other forms of nurture or if nature (genes, sex hormones) drives these developments. Nurture, after all, can have a visible effect on the brain, including the wiring. After all, a social, interactive, stimulating environment is suggested to be beneficial to brain structure.
- Men have larger brain volume and brain weight compared to women on a macroscopic scale. The devil is in the details, however, and it shows a more complex picture (this also applies to the other bullet points below): some regions in women's brains are larger than the corresponding regions in men's brains, and the other way around.
- The planum temporale and Sylvian fissure were found to be larger and longer on average in men than in women. In contrast, the volumes of the superior temporal cortex, Broca's area, the hippocampus, and caudate were significantly larger in women. The midsagittal areas and fiber numbers of the anterior commissure (connecting the temporal lobes) as well as the massa intermedia (connecting the thalami) were found to be larger in women than in men.
- In a study with participants in the 44-77 year age range, men apparently have on average higher raw volume and raw surface areas than women, but at the same time, there was a considerable overlap between the sexes. As well, subregional differences were not at all attributed to brain size. Males also had a larger variance across raw structural measures.
- Men have a higher percentage of white matter whereas women have a higher percentage of gray matter.
- Women have significantly better connected neural networks compared to men's neural networks, according to a study on people aged 22-35. According to a study in youths (8-22 years) male brains are optimized for intrahemispheric communication, while female brains for interhemispheric communication.
- Male and female brains age in different ways, with males preserving more grey matter in the occipital region and women in bilateral inferior frontal lobes, anterior cingulate gyrus, medial thalamus, and hypothalamus.
It is widely established in scientific literature that men and women on average perform differently in some cognitive tasks, although there is large overlap in performance between the sexes. Men show higher spatial intelligence, performing better in tests regarding spatial visualization, spatial perception and mental rotation; while women have higher performance in verbal abilities, including speech, writing, and reading.
It can be argued that these differences in mental abilities are not biological but are the result of culture. That is, society pushes and trains males in spatial reasoning and females in verbal thinking. In this regard, studies with young children are very important, because young children have null or very low cultural conditioning/training.
A 2003 study on a sample of 1,279 children and adolescents, 637 males and 642 females, ranging in age between 5 and 19 years, found that females perform higher on certain verbal tasks and males perform higher on certain spatial tasks. This result is consistent with previous studies regarding male/female mental abilities. However, the age ranges from these studies consist of people that have experienced considerable cultural conditioning.
A 2006 study on a sample of 38 male and female children, 3, 4, and 5 years old, showed that males performed better than females in a spatial task involving the search of a hidden object, and that the male scores increased with age, while the female scores did not. A previous 1999 study on a sample of 288 male and female children, 4 to 7 years old, found a significant male advantage in tests involving mazes and spatial rotations of shapes. However, in both articles it was clear that among the youngest participants (3-4 years old) there were no sex differences yet.
Now the question is: why do these sex differences pop up as children age?
A 2005 study revealed that among boys and girls of low socio-economic status their performance in aerial map tasks and mental rotation tasks showed no significant difference. Reasons for the lack of sex differences among children of low socio-economic status (or rather the existence of them among children of high socio-economic status) were given in the article. The authors suggested that boys and girls in high social-economic status have more access to activities promoting spacial skills (as Legos™, puzzles, video games…), and that boys may engage more in these activities because of biological or environmental reasons, getting better at them.
Another study also explored where this gender difference in spatial cognition among children of higher socio-economic status could come from. Although girls showed equal interest in puzzle play, parents were much more supportive when their sons showed interest in puzzle play, which enhanced the quality of the experience for boys disproportionately. This indicates that there are no biological differences between the sexes regarding their willingness to play games that involve spatial cognition.
Cross-cultural psychometrics studies have shown differences in the distributions of personality traits between men and women.
On the scales measured by the Big Five personality traits, women consistently report higher neuroticism (psychological stress, anger, anxiety, and depression), agreeableness (compassion and cooperativeness), and openness to feelings; while men report higher assertiveness (self-assuredness and confidence without aggressiveness) and openness to ideas. These sex differences in personality traits can be detected in early childhood and remain fairly constant across adulthood. Moreover, these sex differences in personality traits are larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with men. In particular, Asian and African cultures generally show the smallest sex differences, while European and American cultures (in which living standard and gender equality indexes are higher) show the largest differences.
On average the personalty trait of Machiavellianism, characterized by a duplicitous interpersonal style, a cynical disregard for morality, and a focus on self-interest and personal gain, is higher in males than females. In particular, men are overrepresented among high Machiavellians, while females are overrepresented among low Machiavellians.
Females are on average higher than males in extraversion, anxiety, trust, tender-mindedness (e.g., nurturance), and males are on average more assertive and have higher self-esteem. Women are also more sensitive to punishment and men higher in sensation seeking and risk-taking.
Studies consistently show that women are more prone to express their emotions, both positive and negative, than men. Such results are not entirely consistent across national and generational boundaries.
Women as compared to men report higher fear ratings for all objects and situations related to phobias as enclosed spaces, darkness, flying, heights, spiders, snakes, injections, dentists and/or injuries. Women also report more intense feelings of anger in relation to terrifying situations involving a male. In addition, studies consistently find that women tend to have much higher levels of fear of crime than men.
Women cry more intensely than men. The reasons for crying differ between the two genders as well, with men crying more in situations of positive appraisal and loss, and women crying more in situations of conflict. However, this need not be considered a biological difference between the sexes per se. It is theorized that men seek ways to deal with their emotions through instrumentation and organization, as opposed to women who seek to deal with their emotions through personal support groups. Additionally, some of the scientific research has shown that male and female differences in crying is related to the ways in which they are reared. Though doubts have been raised as to this theory, the only recourse when it comes to biology involves resorting to clichés like women's more empathic skills and evopsych nonsense like men crying was dangerous for the tribe and for women. Evidence of women facing more sexual assault than men also has to be admitted into the equation, and cannot be dismissed so easily.
A meta-analysis study by the German Society of Ophthalmology reports that the average woman cries between 30 and 64 times a year, and the average man cries between 6 and 17 times a year. Boys and girls cry around the same rate until age 13. With that being said, the reasons for such weeping are still inconsistent. Biological explanations have proven to be lacking as there have been similarities between pregnant women whose bodies produce more of the hormone prolactin and those lacking said hormone. As well, though it's commonly said that women use their tears to manipulate people, evidence is lacking, as more often than not, apparently people cry alone to themselves rather than in public arenas.
In relationships, men and women tend to be nearly equal when it comes to bargaining tactics across the board on a wide spectrum of areas, such as reason, charm, giving into the other to make them feel better, to actual threats whether they be physical or emotional, but women are more likely to sulk and cry in order to get their way than men.
Psychological studies have found better memory in women than men for emotional events. According to a 2002 MRI study, highly emotional pictures (like pictures of mutilated bodies) are remembered best, and remembered better by women than by men. In particular, men and women activated different neural circuits to encode stimuli effectively into memory even when the analysis was restricted to pictures rated equally arousing by both groups.
A 2014 meta-analysis found that: "it is clear that there are sex differences in empathy from birth, and sex differences appear to be consistent and stable across the lifespan (e.g., Michalska et al., 2013; O’Brien et al., 2013), with females demonstrating higher levels of empathy than males, and children who are higher in empathy early in development continue to be higher in empathy later in development (Eisenberg et al., 1999). This developmental stability suggests that sex differences are unlikely to be caused exclusively by postnatal experiences (e.g., maternal care), but rather reflect some evolutionarily important difference between males and females that is present, at least in some form, from birth, consistent with reports that empathy is moderately heritable (e.g., Baron-Cohen, 2002; Chakrabarti and Baron-Cohen, 2013; Knafo et al., 2008; Rushton, 2004; Zahn-Waxler et al., 1992a,b; Zahn-Waxler et al., 2001)." Regarding the claim that sex differences in empathy are "stable across the lifespan", it is worth mentioning that the authors cite a study of Michalska which actually says that such differences "widens from childhood to adulthood."
For example, a 2000 study on 102 randomly selected neonates (58 female, 44 male), with a mean age of 36.7 hours, found that males have stronger preferences for looking at a mechanical object than a human face, while for females is the opposite.
Similarly, a 2009 study on 30 infants (17 males and 13 females), with a mean age of 5.76 months, compared the visual preference for a toy truck and a doll, and found that males focus more on the former while female focus more on the latter.
That being said, it doesn't need to be the case that these sex differences are inherently biological. Much ado has been made about faulty science involving infants and their being influenced by their caretakers, as well as reading too much into the perceptions themselves and using that to promote the idea that said causes are biological without accounting for the way infants are reared from the beginning can affect the way they act. For example, in an experiment where caretakers raised a child whose sex was unknown to them, when they were told it was a girl, they encouraged play with dolls and spoke gently, while when told the child was a boy, the caretakers were less verbal and encouraged play with trucks. In addition, parents often raise their children in stereotypical ways relative to their gender. As well, let's accept the explanation for once that there are genetic differences in babies relative to people vs things. The elephant in the room becomes apparent when you consider these were one day old infants. The final nail in the coffin is that it becomes a wide leap to say that, all criticisms notwithstanding and assuming the science is sound, that it is quite a leap to say that boys are necessarily more things-oriented or girls are more people-oriented. As well, it is also quite the assumption to say that the infants in question empathized more with people or things. It could just as well be proposed that the infants in question had longer time to habituate themselves when it comes to perceiving people and things they didn't understand.
In adults, a 2009 meta-analysis using career related interest inventories found that men were more likely to respond to thing related professions, versus women who favored people related professions more. Specifically that men show stronger realistic and investigative interests, and women showed stronger artistic, social, and conventional interests. Sex differences favoring men were also found for more specific measures of engineering, science, and mathematics interests. The study in question used a list of career related interest inventories to gauge these findings. It was also found that the way these career related interest inventories were constructed could affect said interests. It does not mean that these differences were innate.
In addition, another study by the same authors analyzed the disparity in STEM (science, technology, engineering and math) between men and women, and found that interests between genders do indeed seem to explain much of the lopsided representation of men vs women in STEM. There are more men in engineering disciplines and more women in medical and social science disciplines. If the people/things dichotomy is accepted, then there are more opportunities for intervention to facilitate wider representation within the various disciplines, rather than the dead-end answer that these explanations are biological and there is nothing that can be done to fix these problems. Indeed, the same authors in an email to the Verge when their studies were raised in the James Damore fiasco, suggested that women are more different from each other on an individual level, than they differ from the sum population of men.
Also, another study has taken issue with the people vs things dichotomy entirely, suggesting that men and women overall are more balanced and have more in common with each other than they are different.
Psychological conditions and disorders
Although men and women may suffer the same mental health disorders, some illnesses are more common in men than women, and vice versa. This could be because of biological differences between male and female brains, and theories in such regard have been proposed, or it could be because the same mental illness is more diagnosed for a sex than the other, although it occurs with the same frequency.
- Anorexia is about eight times more common in females.
- Antisocial personality and substance use disorders are more prevalent in men. Narcissism is also more common in men; about 8% of men and 5% of women by one estimate suffer from narcissism. Borderline personality disorder and histrionic personality disorder are more common in women.
- Most anxiety and mood disorders are more frequent in women.  However, bipolar disorder is equally common in both sexes and males with bipolar disorder tend to have more severe symptoms, in particular mania. Some studies have also found gender parity among adults with obsessive compulsive disorder.
- Attention deficit hyperactivity disorder (ADHD) is diagnosed three times more often in males. An evolutionary explanation could be that some women are more attracted to males displaying hyperactivity and impulsivity, increasing the frequency of genes that predispose males to ADHD. Despite this, the actual amount of ADHD between male and female (as opposed to diagnosed) is believed to be more even given that males are more likely to be identified with ADHD than females due to females' having more subtle signs (thus, females often go undiagnosed and skew the ratio).
- Dyslexia is up to three times more prevalent in males. This seems to be related to the different gray matter/white matter ratios in men's and women's brains.
- Schizophrenia is about 1.4 times more prevalent in men than women.
- Autism and Asperger's syndrome are more likely to be diagnosed in boys and men, though there is debate as to whether women are underdiagnosed because models of autism used for diagnosis are generally based on boys, and to how large the gender disparity is, if there is one at all. It could also be that the condition presents differently in men and women.
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