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The evidence for substantial innate sex differences is mounting. I’ve long been a strong advocate for acknowledging this research, instead of trying to ignore it for ideological reasons, such as the postmodern feminist stance that all gender differences are culturally constructed. On the other hand, I usually take a very conservative approach, and write phrases such as “there are certain innate differences that cannot be ignored”. However, I don’t know if that conservative approach is warranted any more. As the research is progressing, it’s becoming increasingly clear that sex differences are substantial, and not limited to a few specific areas.

This doesn’t mean that we forget about culture, or the plasticity of the human brain that allows us to adapt to a range of situations–regardless of our gender. But it does mean that we need to start acknowledging that the very organ that filters our experience of life, and the “software” that runs that organ, are substantially different between an average man and an average woman. This also means that the inner experience of being a man is different from the inner experience of being a woman.

Recently I was sent a very interesting link about new research that has been carried out to map the relationship between gender, testosterone and risk aversion (Gender differences in financial risk aversion and career choices are affected by testosterone. Paola Sapienzaa, Luigi Zingalesb and Dario Maestripieri, 2009). The strength of this research is that it connects a well known gender specific variable (testosterone) to a specific behavior (risk aversion). It is one thing to prove that there are innate biological differences between men and women, but it is far more convincing when a biological variable can be shown to directly affect behavior.

Let’s see what they say about the experiment:

Prior research has shown that testosterone enhances competitiveness and dominance, reduces fear, and is associated with risky behaviors like gambling and alcohol use. However, until now, the impact of testosterone on gender differences in financial risk-taking has not been explored.

The researchers, using an economic-based measure of risk aversion, found that higher levels of testosterone were associated with a greater appetite for risk in women, but not among men. However, in men and women with similar levels of testosterone, the gender difference in risk aversion disappeared. Additionally, the researchers reported that the link between risk aversion and testosterone predicted career choices after graduation: individuals who were high in testosterone and low in risk aversion chose riskier careers in finance.

In other words, the levels of testosterone that men routinely have, lead to increased risk taking, compared to the levels of testosterone that women usually have. Women who have higher than normal levels of testosterone, approach the risk taking behavior of men, simply by having increased levels of this hormone.

This is not to say that there aren’t a range  of other factors that can increase or decrease risk taking, but those factors in no way detract from the result of the researchers.

Additionally, the study demonstrated that prenatal levels of testosterone, which are much higher in boys, have an impact on risk aversion later in life:

A similar relationship between risk aversion and testosterone was also found using markers of prenatal testosterone exposure.

At this point in time, it is irresponsible to maintain the claim that sex differences are completely, or for the most part, socially constructed.

The updated list of the different research methods that support innate sex difference is thus:

1. Mapping brain structure and function using new imaging techniques such as PET (positron emission tomography) and fMRI (functional magnetic resonance imaging)
2. Studying the behavior of newborns or infants
3. Studies from the field of evolutionary psychology
4. Cross-cultural studies
5. Research that connects innate biological differences to specific behaviors

A friend of mine passed on a very interesting research report to me the other day. It’s called Why Can’t a Man Be More Like a Woman?  Sex Differences in Big Five Personality Traits Across 55 cultures (Schmitt, Voracek, Realo, Allik, 2008). The full report isn’t available online, unless you are a student or a researcher yourself, but I’ll be quoting some relevant passages.

As you may know, I’m interested in the emerging research that investigates the innate differences  between men and women. Even though innate sex differences shouldn’t be overexaggerated, it is a breath of fresh air that we are actually studying these differences, instead of pretending that they don’t exist. The whole gender discourse needs to be infused with solid research — be it biological, sociological or cross-cultural.

Innate sex difference can be studied in a few different ways:

1. Mapping brain structure and function using new imaging techniques such as PET (positron emission tomography) and fMRI (functional magnetic resonance imaging)
2. Studying the behavior of newborns or infants
3. Studying evolutionary psychology
4. Doing cross-cultural studies

Number 2 and 4 are perhaps the two most reliable sources, since differences between newborns are innate by definition, and traits that persist across cultures can hardly be said to be culturally constructed. The article that my friend gave to me, is an excellent example of a cross-cultural study. Let’s see what the authors have to say about personality traits in different cultures:

In many studies, including several meta-analytic investigations, it has been found that men tend to be more assertive and risk taking than women, whereas women are generally higher than men in anxiety and tender-mindedness (Brody & Hall, 2000; Byrnes, Miller, & Schafer, 1999; Feingold, 1994; Kring & Gordon, 1998; Lynn & Martin, 1997; Maccoby & Jacklin, 1974). These sex differences in personality traits can be detected in early childhood (Else-Quest, Hyde, Goldsmith, & Van Hulle, 2006; Wilgenbusch & Merrell, 1999) and remain fairly constant across adulthood (Feingold, 1994; McCrae & Costa, 1984). The effects of these sex differences lead to predictable differences in men’s and women’s leisure behaviors, occupational preferences, and health-related outcomes (Browne, 1998; Collaer & Hines, 1995; Lippa, 2005).
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Observed sex differences in personality traits such as assertiveness and anxiety also appear to be culturally pervasive (Costa, Terracciano, & McCrae, 2001; Lynn & Martin, 1997). Feingold (1994) found that women in Canada, China, Finland, Germany, Poland, and Russia tended to score higher than men on scales related to the personality traits of neuroticism, agreeableness, and conscientiousness. Men, in contrast, scored higher in the extraversion related trait of assertiveness across cultures. In a much larger study, self-report responses to the Revised NEO Personality Inventory (NEO-PI-R) across 36 cultures revealed that women in most countries are higher in several traits related to neuroticism, agreeableness, warmth, and openness to feelings, whereas men score higher on scales measuring assertiveness and openness to ideas (Costa et al., 2001; McCrae, 2002).

In other words: important sex differences in personality traits persist across cultures to an extent that would be highly unlikely if these traits weren’t inborn. This is of course what evolutionary psychologists have been claiming all along, but here we have a wealth of actual research backing up those claims.

However, the study itself was not only about validating these sex difference in personality traits across cultures (though it did that too), it was also about comparing the magnitude of these sex differences in traditional and modern societies. Many of us probably believe that sex differences become smaller in post-traditional societies, due to gender equality and women entering the work force. But this research presents some counter-intuitive results:

Sex differences in most personality traits, however, are not uniform in magnitude across all samples. At times, sex differences can be much larger in some cultures than in others (Fischer & Manstead, 2000; Guimond et al., 2007; Schwartz & Rubel, 2005). One unexpected finding has been that sex differences in personality traits are often larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with men (Costa et al., 2001; McCrae, 2002). Both in self-report and in other-report data, Asian and African cultures generally show the smallest sex differences, whereas European and American cultures—in which living standard and gender equity indexes are generally higher—show the largest differences (McCrae et al., 2005). With improved national wealth and equality of the sexes, it seems differences between men and women in personality traits do not diminish. On the contrary, the differences become conspicuously larger.
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This study provides strong support for the claim that with greater human development and with greater opportunities for gender equality, the personalities of men and women do not become more similar (see also Costa et al., 2001; McCrae, 2002; McCrae et al., 2005). To the contrary, in more prosperous and egalitarian societies the personality profiles of men and women become decidedly less similar. Moreover, these changes appear to result from men’s cross-cultural personality variation. In more traditional and less developed cultures a man is, indeed, more like a woman, at least in terms of self-reported personality traits.

These are interesting findings indeed. The explanation that the authors offer is that in traditional societies, people are restrained by the lack of resources, making individual differences smaller. For example, if everyone is starving, then everyone will be short, but if everyone gets enough food then individual height differences will be more prominent. Similarly, when men and women have ample resources and the freedom to choose their own lifestyles, innate differences will be more prominent than in a traditional society where everyone needs to sacrifice individual needs to help secure food and safety.

Ironically, the more egalitarian we become, the more we can expect men and women to display different personality traits. This may not be what some feminists intended, but it appears to be an unavoidable consequence of “releasing” the innate differences into action.

About a week ago, Time.com featured an interesting article about how the brains of tween girls and boys react to potential social interaction. First of all, it’s interesting to note that the journalist is still trying to be politically correct, and tiptoeing around the facts:

Only in the past few years have scientists been able to use imaging technology to look inside men’s and women’s heads to investigate whether those stereotypical gender differences have roots in the brain. No concrete results have emerged from these studies yet

I suppose you could say that no concrete results have emerged, if you’re expecting a complete brain manual for both sexes and all individuals. However, if by concrete results you mean results that clearly demonstrate that men and women have brains that function differently, and that are structured differently, then yes - concrete results have emerged.

Interestingly enough, after firing off that politically correct introduction, the author proceeds with an almost biologically deterministic statement about the research report on tweens and social interactions:

a new functional magnetic resonance imaging (fMRI) study of children offers at least one explanation for some common tween social behaviors: girls are hardwired to care about one-on-one relationships with their BFFs (best friends forever), while the brains of boys are more attuned to group dynamics and competition with other boys.

I believe that biology is a very real factor in creating gender differences, but it’s important to remember that behaviors are usually a combination of biology, culture and free will. Claiming that biology only is responsible is usually a premature claim, in a world where we still need to work out the details around how biology, culture and free will affect gendered behavior - not to mention how these three factors continously interact.

This caveat aside, the research report becomes yet another piece in the puzzle of the emerging knowledge base around biological brain differences between the sexes:

The results suggest that as girls progress from early puberty to late adolescence, certain regions of their brains become more active when they face a potential social interaction. Specifically, when an older girl anticipates meeting someone new — someone she believes will be interested in her — her nucleus accumbens (which is associated with reward and motivation), hypothalamus (associated with hormone secretion), hippocampus (associated with social learning) and insula (associated with subjective feelings) all become more active. By contrast, boys in the same situation show no such increase in activity in these areas. In fact, the activity in their insula actually declines.

Finally, the author even offers us a potential explanation that is grounded in evolutionary psychology:

Perhaps it’s evidence that evolution has programmed boys to compete within large groups, so they can learn to eliminate rivals for women — and that girls have been programmed to judge, one-on-one, who would be the most protective father for offspring.

As always, it’s good to remember that evolutionary psychology is still speculatory in many ways, especially when it’s used in the context of explaining a research report that wasn’t in itself explicitly examining the validity of an evolutionary psychology claim.

What is evolutionary psychology and why is it interesting in a discourse about gender issues? Marriam Webster defines evolutionary psychology as the study of human cognition and behavior with respect to their evolutionary origins. In other words, the way we think and behave nowadays, may well be adaptations to solve recurrent problems in human ancestral environments.

A simplified way of putting it is that if a behavior or way of thinking was advantageous for thousands of years (for example during the stone age), then it may well have been hardwired into the human brain. We are not born as blank slates, and it makes sense that the programming that we are born with be useful for our survival and reproduction. However, what was useful in the past, may not be useful nowadays, even though the programming remains in our brains.

Evolutionary psychology can be a controversial field. Its proponents want to explain all human behavior using this theory, while its detractors emphasize the importance of human flexibility and continuous biological adaptation to the current cultural climate. In my opinion, the truth is somewhere in between those two polarities, and I leave it up to you to determine what importance you want to allot to each stance.

Let’s have a look at some of the basic principles of evolutionary biology and how they relate to gender issues:

• Since women are the ones who get pregnant (since times immemorial…), women have always been forced to choose a man carefully. A woman can only carry one child at a time, and a pregnancy takes nine months, which means that she’d better choose a man with good genes, because she won’t get very many chances to pass on her own genes. She also needs a man around who’s willing to protect and provide for the child, be it the father or a man who thinks he is the father. This means that the emotional connection to the man is crucial for a women, because the emotional connection is a good indicator of whether he’ll stick around or if he’s only interested in sex.
• The principle above changed with the introduction of the female birth control pill, which enabled women to have sex without risking pregnancy. However, the old dynamics are still part of female nature, competing with the new dynamics that the pill introduced. This means that to some extent women are still looking for a confident man who can be a good protector, and preferably a man who can provide for the child - even if she’s only interested in a sexual relationship, and not in having children.
• Men, however, do not get pregnant and therefore don’t need to choose their sexual partners as carefully. Fathering a bastard child could potentially be done at a very low cost, if you don’t have to assume the role of father for that child. However, being a committed father has always been a very good option for men, since in past eras the survival rate of your children was much higher if you stuck around.
• Since men can father a child at a very low cost while women cannot, women end up being the sexual selectors more often than men.
• Men are attracted to beautiful women. Beauty in this case is not some kind of esoteric concept, it is simply another word for proportional and symmetric facial features. Since women instinctively know that their looks are important when attracting a man, we have a whole cosmetic and plastic surgery industry catering to the needs of women. Evolutionary speaking, men are attracted to female beauty, due to symmetric facial features being a predictor of good health in the past, and good health is crucial if a woman is to survive a pregnancy, and pass on the man’s genes.
• Gay men generally care more about their looks than straight men, and know more about grooming and skin care. The reason for this is simple: gay men are looking to attract other men, and even if those other men are also gay, they are still 100 percent men - and therefore attracted to good looks. Lesbian women, on the other hand, are often more relaxed about their looks, since they are attempting to attract other women, and women care less about good looks (even though good looks are still far from unimportant).

Human beings are wonderfully flexible, adaptive and responsive creatures who can display an amazing range of behaviors, that shift according to the surrounding environment. The malleability of humans beings is so impressive that the belief that there are no inborn traits, only learned traits and adaptations, is understandable.

In the case of David Reimer (born as Bruce Reimer) the belief that there are no behavioral or brain differences between the sexes was taken to its extreme. Bruce was the victim of a circumcision (performed using an unconventional method) that went horribly wrong, leading to his penis being burnt to the extent that it could not be salvaged. His parents, distraught over the incident, were desperately looking for a way forward when an apparent solution revealed itself.

One night, the Reimers see a television profile of an American doctor and his theories on sex and gender. Dr. John Money of Johns Hopkins University in Baltimore argues that boys – caught early enough – could be raised to be girls. Nurture and not nature determines a child’s gender, the doctor argued.

Janet Reimer thought it was worth exploring. The family went to Baltimore to see Dr. Money, who decided that Bruce Reimer was a perfect candidate.

It was decided the Bruce would become Brenda, and the doctor castrated him (removed his testicles). The parents were told to raise him as a girl, and that would be the end of it. However, problems quickly arose:

Janet Reimer did her best to raise Bruce as a girl. She dressed him in skirts and dresses and showed him how to apply make-up. But the transformation was anything but smooth. Bruce Reimer didn’t like playing with the other girls – and he didn’t move like one either. He got into schoolyard fistfights. The other kids called him names like “caveman,” “freak” and “it.”

Clearly, the other kids-who had no idea that Brenda had been born as Bruce-felt that s/he wasn’t behaving and playing the way young girls do. What’s even more interesting to note, is that Bruce himself had no idea that he was anything but a girl, and his parents were also raising him the way they would raise a girl. Still, he simply would not pass for a girl, according to his brother:

“The only difference between him and I was he had longer hair.” “I tried really, really hard to rear her as a gentle lady,” Janet Reimer said. “But it didn’t happen.”

Dr Money, on the other hand, was still pretending that the experiment had been a success, and claiming so in scientific journals:

He published an article in the Archives of Sexual Behaviour pronouncing the experiment a resounding success. It became widely known in medical circles as the Joan/John case.

Money wrote: “The child’s behaviour is so clearly that of an active little girl and so different from the boyish ways of her twin brother.”

I guess some people simply don’t know when to quit, and admit that they were wrong…

Things didn’t end well for David Reimer, who committed suicide at the age of 38. Fortunately, science has finally been able to put an end to the “sex-is-nothing-but-a-social-construction” belief.

Around the same time, research was sounding the death knell for the nurture vs. nature theory. Two studies – released by the Johns Hopkins Children’s Center – concluded that it’s prenatal exposure to male hormones that turns normal male babies into boys. The studies “seriously question the current practice of sex-reassigning some of these infants as females…”

Since then, researchers have shown that it’s not only prenatal testosterone that turns the brain into a male brain, the Y chromosome also plays an important part.

Nurture vs nature has been resolved: it’s not either/or, it’s both, and they also interact throughout life.