Challenging the belief that there are no biological differences between men and women in emotions and cognition
There is a lot of scientific evidence for the idea that men and women differ not just in their bodies but also in their minds. These differences are biological, meaning that they are determined by X and Y sex chromosomes and driven by the sex hormones - testosterone in men and estrogen and progesterone in women. However, this does not mean that these differences are unchangeable. They can be reversed by hormone treatment in trans people.
The position I defend here has been dismissed with the term neurosexism. I consider this a political dogma that arose in reaction to the sexist belief that men are more intelligent than women.
Today it is clear that there are no differences in intelligence between the sexes.
However, this should not blind us to the fact that there are important sex differences in emotions, motivation, mental diseases and specific forms of cognition.
These differences are important when addressing health issues. In fact, it is mandatory for any grant proposal submitted to the National Institutes of Health to specifically address sex differences in whatever issue it studies, regardless of whether it is physical or mental, in animals or humans. Sex differences are also highly relevant for the current debates about male violence, transsexuality and masculinity.
How I researched mental sex differences
I am well aware of the neuroscience of sex differences because it was key for my research work on the neurophysiology of pain for the last 25 years.
To write this article, I gathered scientific papers on sex differences by searching PubMed - a gigantic database run by the USA government of every scientific paper on biomedical research. Of the 48 papers I found, I choose for discussion one published recently by John Archer (Archer, 2019) because it offers a most comprehensive and rigorous overview of this topic. It responds to an earlier review (Hyde, 2005) that concluded that psychological differences between men and women are minimal. I also include here references that complement the information in the paper by Archer.
The paper by Archer is a review of meta-analyses. Research papers present data from work done in the lab, in clinical studies, surveys, etc. Meta-analyses compile data from many research papers and do statistics with them to get overall results. Reviews are articles that collect the most important papers on a particular topic and try to extract general conclusions. Therefore, a review of meta-analyses is the best way to summarize the main findings on the issue of sex differences. This one by Archer analyzed 127 meta-analyses, 85 surveys and 4 mixed papers.
Archer summarized his findings in a table that ranks sex differences in four effect sizes, 0 to 4, to denote if they are zero, small, medium, large or very large. Another measure, the summary value, ranges from negative (larger in women) to positive (larger in men). I give these values in parentheses: (2, -0,57) means that 2 is the effect size and -0.57 is the summary value.
For brevity, I do not discuss sexual orientation or differences in sexual behavior. Neither do I dwell into the evolutionary origin of the sex differences, atopic to which Archer gives a lot of attention but that I find a bit speculative. I do briefly discuss the issue of transsexuality.
Cognitive differences
Let’s start by tackling the thorny subject of cognitive differences. As I said above, men and women do not differ in general intelligence. They have similar capacities for memory (0, 0.09) and mathematics (0, 0.09). Women do slightly better is academic achievement (1, -0.25) while men show small advantages in abstract reasoning (1, 0.15) and spatial working memory (1, 0.26). However, there are some differences in specific cognitive abilities.
Women do better in all language-related cognitive abilities, with medium differences in language ability (2, -0.37), reading (2, -0.36) and writing (2, -0.57), and a small difference in verbal reasoning (1, -0.15). They also are better at emotional intelligence (2, -0.47) and face recognition (2, -0.36).
In turn, men are better at spatial abilities (2, 0.48), particularly mental rotation (3, 0.66), understanding how machines work (4, 1.21) and mechanical reasoning (3, 0.98). They also show a slightly better understanding of science (1, 0.28).
Men do not perform worse in all social tasks. They score slightly better than women at talkativeness (1, 0.24), influencing others (1, 0.26) and leadership in projects (2, 0.41). Although men score higher at interrupting (1, 0.15), this is too small to justify it being the main evidence for the existence of mansplaining.
The fact that women are better in language and men are better at mentally manipulating objects seems to be based on deeper preference for people in women and for objects in men. Men are more interested in things (3, 0.97) and engineering (4, 1.11) Women are more interested in people (3, -0.93) and social activities (3, -0.68).
Sex differences in emotions
There are six basic emotions that can be identified by facial expressions is mammals: fear, anger, disgust, surprise, sadness and joy. Sex differences were found in fear, anger and sadness.
Women are more fearful than men, as revealed in fear questionnaires (2, -0.41). These differences are very large when they pertain to fear in real-world situations (4, -1.16). Women are more prone to anxiety (2, -0.59) and social anxiety (2, -0.36). They are also slightly more prone to sadness (1, -0.23) and depression (1, -0.27). Women have better memory for emotional events than men (Canli et al., 2002).
The lesser fearfulness in men may explain their tendency to risk-taking (2, 0.49), based on seeking sensations (2, 0.39) and excitement (1, 0.29). It seems that not only are men less fearful, but they also have a more positive reaction to fear. It can be a source of joy and excitement.
Men also have higher pain thresholds (2, 0.51) and much higher pain tolerance (4, 1.17). Therefore, the stoicism of men - which is considered part of toxic masculinity - is anchored in a biological difference. If men have less fear of pain and are able to tolerate in better, this may contribute to their higher risk-taking.
Regarding mental problems, men score slightly higher for narcissism (1, 0.26). Women have a slightly higher tendency to neuroticism (1, -0.31) and susceptibility to guilt (1, -0.27) and shame (1, -0.29). They also have nightmares more frequency (1, -0.26), which may be explained by their better vividness of visual imagining (1, -0.16) and dream recall (1, -0.24). There are no sex differences in negative emotions (0, 0.03), and attachment style - anxious (0, -0.04) or avoidant (0, 0.02).
When it comes to anger, things get a bit weird. Women get angry as frequently as men (0, -0.003), show the same amount of indirect aggression (0, -0.02), and only slightly less verbal aggression (1, 0.30). However, physical aggression is more frequent in men (2, 0.59). Differences skyrocket when we look at weapon use (3, 0.88), violent crime (4, 1.11), homicide (4, 2.54), intimate partner homicide (4, 1.06), using violent computer games (4, 1.41), sexual aggression (2, 0.62) and rape (4, 2.32).
Why are men more violent?
So, if men get angry as frequently as women, why are they more violent? There are several possible explanations.
Anger is stronger in men, so it is more difficult to control.
Anger is more strongly coupled with physical aggression in men because they are physically stronger.
Men are worse at self-control than women, both when it comes to effortful control - doing something that is hard (4, -1.01) - and inhibitory control - stopping oneself from doing something (2, -0.41).
Because men are less fearful and more prone to risk-taking, they are less sensitive to threats of punishment. Men are also less sensitive to rewards (2, -0.63).
Men are more prone to revenge (3, 0.83), while women are slightly more forgiving (1, -0.28). This is probably related to the higher inclination of men to deliver altruistic punishment (Zheng et al., 2017), as measured in the ultimatum game (Burnham, 2007; Zak et al., 2009; Dreher et al., 2016).
There are forms of aggression that are independent of anger. When a predator hunts, it is in an aroused state, but not angry (Popova et al., 1993; Haller, 2018). Human are predators. Everybody who has gone hunting or fishing can attest to how pleasurable this state is. The calculated, trained aggression of soldiers and warriors is cold, devoid of anger. It is voluntary, and much more dangerous than enraged aggression. However, since women can also be hunters, soldiers and warriors, this form of violence is not exclusive to men.
This information is important to address violence against women. We will not solve these problems unless we recognize that men are biologically different. We also need to stop the “all emotions are okay” nonsense. No, not all emotions are okay. In men, anger and risk-taking need to be carefully managed. Teenage men need to receive a specific education about managing their anger and aggression. Most cultures have specific rituals and training for that. Instead, we encourage men them to express their emotions freely. Then, when their emotions get the best of them, we punish them without mercy.
Sex differences are biological, not cultural
It could be argued that all these differences are social constructs, not natural. Therefore, we can make them go away by changing our beliefs. However, most of these sex differences are found across different cultures and in early childhood, when cultural influences have not taken root.
There is ample evidence that the male hormone testosterone regulates emotions and increases aggression (Archer, 2019):
Testosterone modulates the connection between the amygdala and the prefrontal cortex, which is key to the modulation of aggression. This effect is present since childhood.
High doses of testosterone given to women increased their engagement with angry faces: increased eye contact, increased cardiac rate and lesser avoidance.
Testosterone levels are linked to dominance in men and competitiveness in women.
Testosterone levels are associated with increased risk-taking.
Testosterone given to young women decreased their sensitivity to punishment and fear to angry faces. It increased their performance in spatial manipulation tasks.
Testosterone has a fear-reducing effect in mammals.
Absence of timidity in newborn boys (6-18 months) correlated with testosterone levels in blood from the umbilical cord.
Girls with lower testosterone had higher empathy and connected better with other girls.
Testosterone in newborns of 1-3 months was negatively correlated with their language skills at 16-30 months.
Verbal fluency declined in female-to-male transsexuals after giving them testosterone for 3 months.
Testosterone increased both punishment and gratitude in the ultimatum game, showing that it mediates status-enhancing and pro-social behaviors in men (Dreher et al., 2016).
Women’s emotions change during the menstrual cycle
What about the effect of female hormones? These are not as easy to track as the effect of testosterone because there are two types of female hormones - estrogen and progesterone - and because their levels change during the menstrual cycle. Besides, the menstrual cycle does not extend throughout a woman’s life - it starts with puberty, ends with menopause, and it’s interrupted during pregnancy. Hence, the emotional state of women should be different in each of these phases of their lives. This has long been recognized in popular cultures, but the modern everything-is-a-social-construct dogma has challenged this notion.
There is evidence showing that women’s emotions change during the menstrual cycle:
Women in the follicular phase perceived angry and sad faces more accurately than men or women in other phases, while women in the follicular and ovulatory phases perceived fearful faces better than men (Guapo et al., 2009). Estrogen levels correlated negatively with the perception of anger.
A recent study (Dan et al., 2019) used functional magnetic resonance imaging (fMRI) to measure brain activity and connectivity during the experience of negative and positive emotions. Negative emotions produced more activity in men’s right hippocampus compared to women in the follicular phase, and in men’s right cerebellum compared to women in the luteal phase. Amusement - a positive emotion - reduced the connectivity between the putamen and the prefrontal cortex in women in the luteal phase, compared to men. Women in the luteal phase were more prone to sadness and less inclined to amusement, suggesting that during this phase of the menstrual cycle there is reduced pleasure and reward.
Sex hormones have effects at the molecular level
It has been known for some time that the steroid sex hormones testosterone, estrogen and progesterone have effects on the cells of the nervous system, neurons and glia.
Steroids present in the central nervous system have been called neurosteroids and are able to bind to GABAA receptors. These are proteins that bind the neurotransmitter gamma-amino-butyric acid (GABA), as well as several important drugs like the benzodiazepines (Valium, Rohypnol) and the barbiturates (pentobarbital). GABAA receptors decrease neuronal activity - GABA is the main inhibitory neurotransmitter in the brain. They play a major role in decreasing anxiety.
Steroids - including testosterone, estradiol and progesterone - also have specific receptors in neurons, some located at the cell membrane and others in the nucleus. Steroid receptors regulate gene expression in neurons.
But what about trans people?
That sex differences are biological does not mean that they are unchangeable. The scientific evidence that I presented here shows that they are mediated by sex hormones. Therefore, the sex hormone treatments that transsexual people undergo during their transition change their brains, just like they change their bodies. Indeed, trans people experience profound changes in their emotions as they transition. Their minds change to match their desired sexual identity in ways that mere changes in behavior and appearance cannot possibly match. This supports the idea that men and women do have different minds.
Trans women are women. Trans men are men. In their bodies and their minds. Biologically and socially.
Some important implications
I have presented scientific evidence that men and women are different not just in their bodies but also in their minds. The much maligned book Men Are From Mars, Women Are From Venus was right in the basics, although perhaps not in all the details.
The differences between men and women may be the largest inside the human species, far surpassing the differences between races. This is known in biology as sexual dimorphism. It is low in some species, but so high in others that males and females look like completely different animals. Think about peacocks, Siamese fighter fish, guppies, mallard ducks, hens and roosters.
Sexual dimorphism is high in all ape species. Male gorillas are much larger and far more aggressive than the females. The same can be said, to a lesser extent, about chimps. Male orangutans have huge face plates and are more solitary than the females. In fact, humans are the ape species with less sexual dimorphism, but this doesn’t mean it is completely gone.
The specter of male superiority is dispelled when you look at the list of sex differences. In all important cognitive attributes, women score the same as men. The higher emotional and verbal intelligence of women more than balance the higher spatial intelligence of men. If anything, men come out looking worse than women due to their propensity for violence. However, there is a positive side to aggression, since it can be sublimated into the qualities of assertiveness and intensity. This article is not an argument for female supremacy, either.
The different emotional stiles of men and women are highly relevant for the current debate on male aggression, gender and masculinity.
Some food for thought
Masculinity and femininity are based on biology and are not social constructs. Therefore, bashing masculinity is an attack on personal characteristics that are as basic as sexual orientation. It should be considered a form of bigotry.
Many of the attributes listed under “toxic masculinity” - like stoicism, lesser sociability, lesser empathy, dominance and aggression - are, in fact, intrinsic of being male. They need to be treated with the same understanding as the biological disadvantages of women - such as lower pain tolerance and higher fear and anxiety.
The biological propensity of men to violence need to be recognized and addressed. Young men need to be educated since puberty in how to control their anger and aggression, instead of being told that “all emotions are natural”.
We all need to learn about the different emotional and cognitive styles of the opposite sex and use that knowledge to improve our relationships with friends, coworkers and intimate partners.
Gender may be a social construct, but it is built upon a solid biological sex binary. Attempts to deconstruct gender disregarding the biological reality of sex differences risk fighting against some of the basic things that make us human.
References
Archer J (2019) The reality and evolutionary significance of human psychological sex differences. Biological reviews of the Cambridge Philosophical Society 94:1381-1415.
Burnham TC (2007) High-testosterone men reject low ultimatum game offers. Proceedings Biological sciences 274:2327-2330.
Canli T, Desmond JE, Zhao Z, Gabrieli JD (2002) Sex differences in the neural basis of emotional memories. Proc Natl Acad Sci U S A 99:10789-10794.
Dan R, Canetti L, Keadan T, Segman R, Weinstock M, Bonne O, Reuveni I, Goelman G (2019) Sex differences during emotion processing are dependent on the menstrual cycle phase. Psychoneuroendocrinology 100:85-95.
Dreher JC, Dunne S, Pazderska A, Frodl T, Nolan JJ, O'Doherty JP (2016) Testosterone causes both prosocial and antisocial status-enhancing behaviors in human males. Proc Natl Acad Sci U S A 113:11633-11638.
Guapo VG, Graeff FG, Zani AC, Labate CM, dos Reis RM, Del-Ben CM (2009) Effects of sex hormonal levels and phases of the menstrual cycle in the processing of emotional faces. Psychoneuroendocrinology 34:1087-1094.
Haller J (2018) The role of central and medial amygdala in normal and abnormal aggression: A review of classical approaches. Neurosci Biobehav Rev 85:34-43.
Hyde JS (2005) The gender similarities hypothesis. The American psychologist 60:581-592.
Popova NK, Nikulina EM, Kulikov AV (1993) Genetic analysis of different kinds of aggressive behavior. Behavior genetics 23:491-497.
Zak PJ, Kurzban R, Ahmadi S, Swerdloff RS, Park J, Efremidze L, Redwine K, Morgan K, Matzner W (2009) Testosterone administration decreases generosity in the ultimatum game. PLoS One 4:e8330.
Zheng L, Ning R, Li L, Wei C, Cheng X, Zhou C, Guo X (2017) Gender Differences in Behavioral and Neural Responses to Unfairness Under Social Pressure. Scientific reports 7:13498.
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