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Cognitive differences between sexes

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Differences in male and female cognitive abilities are widely established in the current scientific literature.[1][2][3][4][5][6] 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:

  1. 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.
  2. 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 are consistent with 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.
  3. 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 complicate, 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.[7]

Brain anatomy[edit]

Average brain weight by sex and age

Research shows that mature male and female brains are very different.[8] Scientists have found about 100 gender differences in the brain,[9] regarding processing, chemistry, structure, and activity. The most notable of these differences are the following:

  • On average, men have larger brain volume and brain weight com­pared to women, which is only partly accounted for by larger body dimensions in men.[8]
  • Men have a higher percentage of white matter whereas women have a higher percentage of gray matter.[10][11]
  • Women have significantly better connected neural networks compared to men's neural networks, according to a study on people aged 22-35.[12][13] According to a study in youths (8-22 years) male brains are optimized for intrahemispheric communication, while female brains for interhemispheric communication.[14]
  • 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.[15]

It remains speculation to what functions these differences correspond, and whether they're a result of genes, sex hormones or culture (gendered upbringing), since nurture can have a visible effect on the brain[16]

Cognitive tasks[edit]

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.[17] Men show higher spatial intelligence, performing better in tests regarding spatial visualization, spatial perception and mental rotation;[18][19][1][20][6] while women have higher performance in verbal abilities, including speech, writing, and reading.[2][3][4][21][5]

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.[22] This result is consistent with previous studies regarding male/female mental abilities.[23][24][25][26] However, the age ranges from these studies consist of people that have experienced considerable to a lot 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.[27] 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.[28] However, in both articles it is clear that among the youngest participants (3-4 years old) there are 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-economical status their performance in aerial map tasks and mental rotation tasks showed no significant difference.[29] Reasons for the lack of sex differences among children of low socio-economical status (or rather the existence of them among children of high socio-economical status) were given in the article. The authors suggested that boys and girls in high social-economial 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 enviromental reasons, so getting better at them.

Another study of Levine in the same year explored also where this gender difference in spatial cognition among children of higher socio-economical 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 disproportionally.[30] This indicates that there are no biological differences between the sexes regarding their willingness to play games that involve spatial cognition.

IQ[edit]

See the main article on this topic: IQ

Statistical data shows that there is no significative difference between the average IQ scores of men and women.[31][32][33] However, the variance of male scores is higher than that of females, hence more males than females are in the top and bottom of the IQ distribution.[34]

Psychology[edit]

Personality traits[edit]

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 traitsWikipedia's W.svg, 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.[35][36][37][38][39] These sex differences in personality traits can be detected in early childhood[40][41] and remain fairly constant across adulthood.[42] Moreover, these sex differences in personality traits are larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with men.[35][43] 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.[44]

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 over-represented among high Machiavellians, while females are overrepresented among low Machiavellians.[45][46]

Accordingly to 2014 meta-analysis including 355 studies from 13 countries, the personality trait of narcissism is higher in males than females.[47]

Females are on average higher than males in extraversion, anxiety, trust, tender-mindedness (e.g., nurturance), and males on average to more assertive and have higher self-esteem.[48] Women are also more sensitive to punishment and men higher in sensation seeking and risk-taking.[49]

Emotions[edit]

Studies show consistently that women are more prone to express their emotions, both positive and negative, than men.[50] [51] [52]

Females report experiencing emotion contagion (feeling the same emotions of those around them) more often than males.[53][54]

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.[55] Women also report more intense feelings of anger in relation to terrifying situations involving a male.[56] In addition, studies consistently find that women tend to have much higher levels of fear of crime than men.[57][58]

Accordingly to more than 14 studies in the scientific literature, women report a greater propensity to cry, a greater actual crying frequency and more intense crying than do men.[59] A meta-analysis study of 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.[60][61] Furthermore, women tend to use crying and whining (regression tactic) more frequently as a way to manipulate others than do men.[62]

Also, on average women are better than men in emotional interpretation, such as understanding facial expressions.[63][64]

Interests[edit]

Studies show that on average, since from an early age, females are more interested in people-related activities than things-related activities, while for males is the opposite situation.[65][66]

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.[65] The results of this research demonstrate that these sex differences are in part biological, since at such a young age they cannot be due to social or cultural factors. 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.[66]

In adults, a 2009 meta-analysis found that men prefer working with things and women prefer working with people. Precisely 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.[67]

Mental health disorders[edit]

Although men and women may suffer the same mental health disorders, some illnesses are more common in men than women, and vice versa, though in some cases, including ADHD, there can be under-representation that can skew the ratio.

  • Anorexia is about eight times more common in females.[68]
  • Antisocial personality and substance use disorders are more prevalent in men.[69]
  • Anxiety and mood disorders are more frequent in women.[69]
  • Attention deficit hyperactivity disorder (ADHD) is diagnosed three times more often in males.[70][71] 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.[72][73] 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.[74]
  • Schizophrenia is about 1.4 times more prevalent in men than women.[75][76][77]

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