Do Men and Women Have Different Brains?

Why do men and women think differently, express emotions in different ways and exhibit differences in behaviour? These common questions arise in everyday contexts, such as in family dynamics, workplace settings and through our general day-to-day interactions with one another. The area of gender difference has been a controversial topic of debate in the last half-century, as we see shifts in the roles of gender and how they play out in work and life. Nevertheless, to what extent do these differences occur in the 3-pound object we refer to as the human brain? Researchers have been exploring this frontier for decades, searching for the answers that might help define our place in this complex society in which we live. When drawing these distinctions, it is necessary to take a tri-dimensional approach, exploring the brain’s biological features, and the cognitive competencies and behaviours that manifest as a result.

The differences between the brains of men and women can be observed on a biological level, presenting distinctions in anatomical structure, hormones, and genetic makeup. Studies suggest that the adult brain weighs an average of 1.5 kilograms, with the male brain being about 10% larger than the female brain, weighing 11–12% more than that of a woman (Zaidi, 2010). The ratios of gray and white matter tend to differ, with women having a higher percentage of gray matter and men having a higher percentage of white matter and cerebral spinal fluid (Gur et al., 1999). According to Ho et al., (1980), men have about 176,000 km of myelinated axons by age of 20, and women have about 149,000 km.

Structural differences between the sexes are a result of genetics, with differentiation in XX and XY chromosomal composition. In addition, differences are also attributable to the exposure to hormones circulating during the embryo’s developmental stages in the womb. Depending on the level of hormonal activity during periods of gestation will determine the likelihood for male or female traits. The high presence of androgens is responsible for masculinising the brain, and the lack of androgens results in the feminisation of the brain (Zaidi, 2010). Exposure to hormones during gestation have shown to predict gendered behaviour three decades later (Udry, 2000). These distinctions in biological features appear to have implications in our cognitive competence, interests, and social behaviours.

Women and men appear to show differences in cognitive competence resulting from their unique neuroanatomical features. According to Kimura (1992), women perform better in verbal memory tasks and verbal fluency tasks, and show higher speeds of articulation in their language. The temporal and parietal areas of the cortex that are associated with language are more significant in volume in women (Geary, 1998). In addition, MRI studies have shown that women have larger brain volume than men in the two regions of the brain related to speech — Broca’s and Wernicke’s area (Schlaepfer et al., 1995). In terms of intelligence, IQ correlates with gray matter volume in the frontal lobe and Broca’s area for women (Haier et al., 2005).

In contrast, men outperform women in math and geometry (Denckla et al., 1985). Men also have an advantage over women in visual-spatial abilities and their ability to identify 3D objects rotated in space (Grabowska, 2017). According to Grabowska (2017), the parietal lobe plays an integral role in spatial processing and mental rotation. Men have a larger surface area in this region of the brain. Evidence suggests that intelligence quotient (IQ) correlates with gray matter volume in the frontal and parietal lobes for men (Haier et al., 2005). These differences do not suggest that one brain operates better than the other does, as both sexes tend to score quite similarly in intelligence quotient tests. Instead, it posits that men and women use different brain areas to achieve similar IQ outcomes. These differences in cognitive competence may play a role in the choice men and women take regarding personal and career interests.

The differences between women and men are evident through personality traits and interests. The Big 5 Personality domain of agreeableness comprises qualities relating to altruism, a tendency toward cooperation, social harmony and consideration of the concerns of others. On average, women are more agreeable than men, scoring higher in both the agreeableness sub-traits of politeness and compassion (Weisberg et al., 2011). Perhaps, some of these differences result from gendered socialisation; however, there is evidence to suggest that these differences are found consistently across cultures. According to Costa et al. (2001), women scored higher than men did in agreeableness in 25 of 26 nations. These prosocial traits common to women are indicative of their people-orientated interests. Beltz et al. (2011) found that, on average, women prefer occupations involving work with people, like; counselling, teaching, social work and nursing.

In contrast, on average, men score higher in the Big 5 personality sub-trait of extraversion known as assertiveness (Weisberg et al., 2011). Assertiveness is a personality trait that reflects agency and dominance. According to Lippa (2010), men are more competitive, arrogant and dominant compared to women. The less nurturing traits of men may have some relation to their occupational interests, which tend to be thing-orientated. Men prefer occupations related to objects, such as; auto mechanic, trades and engineering (Beltz et al., 2011). These findings have proven to be consistent across 53 nations (Lippa, 2010). The functional significance of these differences are assessed further on a behavioural and cognitive level, providing a deeper insight into these differences and the implications of these differences on both the individual and collective level.

The functional significance of the different brain genders is evident through social cognition and behaviour. A crucial component of social cognition involves one’s ability to engage in empathic thinking, or identify and appropriately respond to another person’s emotions and thoughts. According to Grabowska (2017), women present higher levels of social awareness skills, which may result from their high density of mirror neurons that are located in regions of the brain associated with empathy and reception of social signals. According to Baron-Cohen (2003), the female brain is hard-wired predominantly for empathy, and as a result, they highly value altruism and reciprocal relationship dynamics. Women have an advantage over men in human relations and perform better at recognising emotional overtones in the verbal language (Zaidi, 2010). In addition, women have an advantage in nonverbal emotion recognition, and this, in conjunction with higher levels of empathy, correlates positively with prosocial behaviour (Christov-Moore et al., 2014). Jaffee and Hyde (2000) found that females exhibit higher prosocial moral judgment levels and are more sophisticated in prosocial moral reasoning. These prosocial behavioural and cognitive patterns are further evident on a neurobiological level. According to Soutschek et al. (2017), dopaminergic neural reward systems appear to be more sensitive to prosocial rewards over selfish rewards in women, proposing that women find more value in sharing.

In contrast, the male brain is less hard-wired for empathy and more for understanding and building systems (Zaidi, 2010). Men are higher in independence, dominance and rank-related aggression, and value power, politics and competition (Ahlgren and Johnson, 1979). Evidence suggests that males are more aggressive and are more direct with their aggression, making them more likely to engage in hitting, pushing and striking (Zaidi, 2010). They also display higher rates of antisocial behaviour (Lippa, 2010). Unlike women, men tend to be more interested in self-reward over shared reward. Dopaminergic neural reward systems in men appear to be more sensitive to self-rewards over prosocial rewards, suggesting that men find more value in non-sharing selfish reward (Soutschek et al., 2017). Evolutionary theories propose that these traits and interests are a product of evolved sexually selected traits that aid in raising children in the case of women and aid men in their pursuit for dominance, status and attracting mates (Lippa, 2010). These differences may serve in our surviving and thriving as a species, particularly in the context of our highly complex social arena.

Many believe that defining gender differences in the brain is not scientifically sound and acts as a provocative means to harmful gender stereotypes. With such controversial topics has emerged terms such as “Neurosexism” (Fine, 2008). While controversial, the introduction of new technologies over the last decade has provided a platform for growing evidence to suggest that there are, in fact, inherent differences in how men and women’s brains are wired and how they operate. This does not suggest that one gendered brain works better than the other does. Instead, it outlines how these fundamental biological differences contribute to the differences in our cognition and behaviour. We must not ignore these distinctions in the name of political correctness, as these insights provide a potential pathway to higher levels of precision in psychiatric practice and improvements in the way we accommodate each other’s needs, both individually and collectively.

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