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. Additionally, the differences between the sexes can often be overstated as well as ignoring that the genders can often overlap, to say nothing of transgender people, whose brains often match the opposite gender rather than their designated sex at birth.
  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.

Brain anatomy[edit]

Average brain weight by sex and age

Research shows that mature male and female brains are very different.[7] Scientists have found about 100 gender differences in the brain,[8] 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.[7]
  • Men have a higher percentage of white matter whereas women have a higher percentage of gray matter.[9][10]
  • Women have significantly better connected neural networks compared to men's neural networks.[11][12] Also, male brains are optimized for intrahemispheric communication, while female brains for interhemispheric communication.[13]

However, 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[14]

There is no research to be found on the effects of sex hormones on brain development, so no conclusions can be drawn regarding this. However, recent research shows there is little difference in male and female brains of infants of 1 month age with the exception of overall brain volume (which can simply be explained by the fact that male infants grow larger on average, which ís a result of sex hormones).[15] So (however more research should be done in order to be more certain of the following statement) from this it can be concluded that sex hormones have nothing to do with the development of the relative structure of the brain, and that most of the brain differences stated above are due to culture. Here it is assumed that the absence of effect of sex hormones on the brain anatomy remains the same after birth, but (although a research that assures this would be nice) this assumption is not a very bold one. All this however does not deny that sex hormones have an effect on the regulation of parts in the brain, which might explain some of the differences in behavior and (correlation in) sexual preference perceived between men and women.

Cognitive tasks[edit]

It is widely established in scientific literature that, statistically speaking, men and women perform differently in some cognitive tasks. Men show higher spatial intelligence, performing better in tests regarding spatial visualization, spatial perception and mental rotation;[16][17][1][18][6] while women have higher performance in verbal abilities, including speech, writing, and reading.[2][3][4][19][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.[20] This result is consistent with previous studies regarding male/female mental abilities.[21][22][23][24] 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.[25] 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.[26] 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.[27] 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:

“Although little is known about what types of input can promote spatial skill, prior studies indicate that activities such as playing with Legos, putting puzzles together, and playing video games are correlated with spatial skill; further, boys spend more time on these activities than girls (e.g., Dorval & Pepin, 1986; Serbin, Zelkowitz, Doyle, Gold, & Wheaton, 1990; Subrahmanyam & Greenfield, 1994). Although low-SES children certainly engage in sex-typed play, they may have less access than other children to toys and games that promote spatial skill, as some of these toys and games are relatively expensive. Prior studies also indicate that freedom to explore the environment is correlated with the male-female discrepancy in spatial ability, and that boys spend more time exploring their neighborhoods than girls do (e.g., Entwisle, Alexander, & Olson, 1994). However, boys from low-SES backgrounds may not be given as much freedom to explore their neighborhoods as their higher-SES counterparts because of parental perceptions of danger in their environment (e.g., O’Neil, Parke, & McDowell, 2001). Thus, in high-SES environments, boys may engage more in spatially relevant activities than girls do, but in low-SES environments, boys and girls may engage in these activities at low and approximately equivalent levels. Such a pattern would provide a possible explanation for the Sex x SES interaction (e.g., Dickens & Flynn, 2001). Although activities that promote spatial skill may be critical to the male spatial advantage, our findings do not distinguish between two potential causes for higher male engagement in these activities. One possibility is that boys engage in spatial activities more than girls do whenever such activities are available because of a biological propensity, and the other possibility is that boys engage more in these activities in certain cultural contexts because their environments make it more comfortable for them to do so. Of course, some combination of these two scenarios is possible. Thus, our findings do not rule out a role of biological factors in the male spatial advantage, but the finding of Sex x SES interactions for two spatial tasks poses a challenge for explanations that downplay the role of environmental effects.” There is really no way to write this any shorter.

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.[28] 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.[29][30][31] 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.[32]

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.[33]
  • Antisocial personality and substance use disorders are more prevalent in men.[34]
  • Anxiety and mood disorders are more frequent in women.[34]
  • Attention deficit hyperactivity disorder (ADHD) is diagonsed three times more often in males.[35][36] 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.[37][38] 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.[39]

References[edit]

  1. 1.0 1.1 Maeda, Yukiko; Yoon, So Yoon (2012). "A Meta-Analysis on Gender Differences in Mental Rotation Ability Measured by the Purdue Spatial Visualization Tests: Visualization of Rotations (PSVT:R)". Educational Psychology Review (1): 69-94. https://doi.org/10.1007/s10648-012-9215-x. 
  2. 2.0 2.1 Scheiber; Reynolds; Hajovsky; Kaufman (2015). "Gender differences in achievement in a large, nationally representative sample of children and adolescents". Psychology in the Schools (4): 335-348. https://doi.org/10.1002/pits.21827. 
  3. 3.0 3.1 Reynolds; Scheiber; Hajovsky; Schwartz; Kaufman (2015). "Gender Differences in Academic Achievement: Is Writing an Exception to the Gender Similarities Hypothesis?". The Journal of Genetic Psychology (3-4): 211-234. https://doi.org/10.1080/00221325.2015.1036833. 
  4. 4.0 4.1 Hirnstein; Coloma Andrews; Hausmann (2014). "Gender-Stereotyping and Cognitive Sex Differences in Mixed- and Same-Sex Groups". Archives of Sexual Behavior (8): 1663-1673. https://doi.org/10.1007/s10508-014-0311-5. 
  5. 5.0 5.1 Kwon, Ho-Beom (2010). "Gender difference in speech intelligibility using speech intelligibility tests and acoustic analyses". The Journal of Advanced Prosthodontics (3): 71-76. https://doi.rg/10.4047/jap.2010.2.3.71. 
  6. 6.0 6.1 Foroughi; Wren; Barragan; Mead; Boehm-Davis (2016). "Assessing Mental Rotation Ability in a Virtual Environment with an Oculus Rift". Proceedings of the Human Factors and Ergonomics Society Annual Meeting (1): 1849-1852. https://doi.org/10.1177/1541931215591399. 
  7. 7.0 7.1 Sex difference in the human brain, their underpinnings and implications. Elsevier. 2010. https://www.elsevier.com/books/sex-differences-in-the-human-brain-their-underpinnings-and-implications/savic-berglund/978-0-444-53630-3. 
  8. Jantz, Gregory L. (2014). "Brain Differences Between Genders: Do you ever wonder why men and women think so differently?". Psychology Today. https://www.psychologytoday.com/blog/hope-relationships/201402/brain-differences-between-genders. 
  9. Allen; Damasio; Grabowski; Bruss; Zhang (2003). "Sexual dimorphism and asymmetries in the gray-white composition of the human cerebrum". Neuroimage (4): 880-94. https://www.ncbi.nlm.nih.gov/pubmed/12725764. 
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  11. Szalkai, Balazs; Varga, Bálint; Grolmusz, Vince (2015). "Graph Theoretical Analysis Reveals: Women’s Brains Are Better Connected than Men's". PLoS ONE (7). https://dx.doi.org/10.1371/journal.pone.0130045. 
  12. Szalkai, Balázs; Varga, Bálint; Grolmusz, Vince (2017). "Brain size bias compensated graph-theoretical parameters are also better in women's structural connectomes". Brain Imaging and Behavior. PMID 28447246. https://dx.doi.org/10.1007/s11682-017-9720-0. 
  13. Ingalhalikar; Smith; Parker, et al (2014). "Sex differences in the structural connectome of the human brain". Proceedings of the National Academy of Sciences of the United States of America (2): 823-8. https://dx.doi.org/10.1073/pnas.1316909110. 
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