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As a comment, I'll just attach my son's recent research assignment as a freshman at UC Santa Barbara. The first point is that boys continue to develop their cognitive abilities in math until 18, whereas girls development slows at 14-15. The second point is that the theory of comparative advantage that you cite (which benefits girls) is based on the assumption of genetic differences -- so you can't have it both ways. Do you believe in genetic gender differences, do you believe in genetic differences only if they favor girls, or do you not believe in genetic differences? Your post doesn't make your own view clear.

Nicolas Jimenez
Writing 2

What is responsible for the disparity between men and women in the sciences?

Larry Summers’s dismissal from Harvard University made it clear that the issue of innate cognitive differences between the sexes is a sensitive one. He was dismissed for the mere suggestion at an informal conference that men may have a genetic edge over women in innate scientific aptitude. His comments did not go well in this era of political correctness and of supposed unhampered striving and achievement. Seemingly, the idea that women may not be as intellectually predisposed as men to have careers in the sciences has been dismissed as a Neolithic idea. However, the literature shows that it is an idea that many leading academics support. The main issue in this debate is whether primarily sociological or biological factors account for the disparity between men and women in the sciences. This paper will argue that the disparity is primarily due to biological differences but that sociological factors amplify it.

The biological differences in cognition between the genders are not immediately apparent. They manifest themselves throughout the genders’ developments. For boys and girls follow significantly different maturation schedules. Generally, girls mature earlier. In the calcification of the teeth, for example, girls begin to accelerate ahead of boys at the age of 6 yr and are about 6 months ahead of boys up to the age of 15, after which boys catch up (Demirjian, 1978). In weight and height, the growth of girls begins to accelerate at about the age of 8 yr. They retain greater average heights and weights than boys up to 15 yr. Sex differences in maturation rates are also present in brain development. The brain size of girls begins to increase relative to that of boys from about the age of 8 yr. The difference in brain size reaches its minimum between the ages of 11-14 yr. From ages 15 to 18, however, boys continue to grow in stature and brain size, while girls are fully mature by age 15 (Rushton, 1992). Matching these facts about different maturation schedules, males only have about a 1.5 advantage in (WAIS) IQ in childhood and adolescence, and about a 4 point advantage in adulthood (Lynn, 1994). Lynn’s surprising finding was replicated by Jackson and Rushton in a study that found that 17 to 18 year old males averaged 3.63 IQ points higher than their female counterparts on the 1991 Scholastic Assessment Test (2006). On these intelligence exams, males generally earn higher scores on some tests of spatial ability, mathematical reasoning, and targeting, while women are often found to average higher on some tests of memory, verbal ability, and motor coordination within personal space (Halpern, 2000).

These findings may seem strange considering the general consensus that there are no intelligence differences between the sexes. Lynn (1994) offers two provocative explanations for this phenomenon: “First [the experts] have forgotten that the human brain has a right hemisphere which houses spatial abilities. Most intelligence tests consist largely of verbal and reasoning problems on which sex differences are much smaller than on spatial problems… The second factor that has misled psychologists is that girls mature earlier than boys, a fact long known in the world of human biology but which has hardly penetrated psychology. Most intelligence test data obtained from children and young adolescents, particularly over the age range 8-14 yr when the earlier maturation of girls accelerates their physiological development and brain size as compared with boys… It is the concentration of attention on the results of verbal and reasoning tests obtained mainly from children and young adolescents that has misled so many psychologists for so many decades to the erroneous conclusion that there is no sex difference in intelligence” (p. 269-270).

Though Lynn’s comments may seem bigoted, a review of the literature supports his claims. Elizabeth Spelke’s paper “Sex differences in intrinsic aptitude for mathematics and science?” (2005) is a perfect example of how faulty generalizations about men and women are made from data extrapolated from children. In her paper, Spelke, a respected authority on psychology who teaches at Harvard University, attempts to refute claims that sex differences exist in mathematical aptitude. She uses data that shows that male and female infants show few cognitive sex differences to argue that “there is no evidence for sex differences in overall aptitude for mathematics or science at any point in development” (pg 950). However, she fails to mention the well established differences in maturation schedules discussed above. Cognitive data collected from infants becomes utterly irrelevant once both sexes have fully matured. Only then do the differences become fully apparent.

Variations in IQ and reasoning abilities between men and women are not the only differences between the sexes. Equally important, men consistently show greater genetic variance than women. For most traits men have a flatter bell curve than women. In other words there are more men than women with traits that lie at the extreme. For example, 80% of individuals with autism are boys. Boys are also four to five times more likely than girls to be diagnosed with Attention Deficit Hyperactivity Disorder (ADHD). Similarly, a study cited by Spelke found over 12 boys for every girl in the top 1% of individuals on the SAT-Math exam (pg. 955).

The assertion that men are far more numerous at the top end of the IQ distribution curve is often interpreted as implying some sort of male genetic superiority. This interpretation should be questioned. In reality, extreme scientific intelligence is a genetic anomaly. If told that a given person is intelligent, popular, and sociable, what would the reader guess that person’s occupation was? It is highly doubtable the reader would choose “theoretical physicist”! Intelligent, popular, and social people are not theoretical physicists. The fact that women are underrepresented in the sciences can thus actually be seen as a genetic edge over males.

In any case, it is not surprising that males outnumber females in science and technology given both slightly greater adult IQs and greater genetic variability amongst. Both of these fields attract extremely bright individuals with often poor social skills – usually men. According to the APA website women account for only 7% of university tenured professors in the field of physics. In engineering, the number hovers is close to 10%.

While the IQ findings are certainly relevant, there are significant problems with the IQ approach to understanding this social phenomenon. The most glaring problem is that IQ is not necessarily correlated with scientific achievement. This is a topic that Malcom Gladwell discusses at length in his book Outliers. Beyond at IQ of about 120, Gladwell states, IQ is only weakly correlated with achievement. Thus, though women may have lower average IQs than males, they should theoretically be capable of comparable achievement in the sciences since they are comparably represented in the category of individuals with IQs above 120 (pg. 56).

In fact, a compelling paper was recently published in Nature that supports the position that discrimination and low expectations are responsible for the disparity. The article was authored by Ben Barres, a professor of neurobiology at Stanford University. A transgendered person, Barres has had the unique perspective of having experienced life both as a male and as female scientist. Barres (2006) notes the changes that took place after undergoing testosterone treatment: “I underwent intensive cognitive testing before and after starting testosterone treatment… my spatial abilities have increased as a consequence” (pg. 135). The biggest difference for Barres, however, was that people treated him with much more respect: “I can even complete a whole sentence without being interrupted by a man” (pg. 135). According to Barres, women in science face many more obstacles than men. They are discriminated against, and they do not receive adequate support from their institutions to help them balance career and family responsibilities. He argues that expectations for girls need to be raised and that girls need to be taught how to survive in a prejudiced world (pg. 135). This is undoubtedly true; society should aim for equal achievement among all its constituent groups, even if that goal is unrealistic or unattainable.

The domain of evolutionary psychology gives us interesting insights into the disparity. Males and females have traditionally assumed different social roles throughout evolution. Males traditionally hunted, fought, and made important decisions, whereas women traditionally scavenged for food and kept social order (Lynn, 1994). In light of this, it would be illogical for the sexes to have the same cognitive profiles. From the onset of puberty, males are flooded with the hormone testosterone, whereas women are flooded with estrogen. Testosterone triggers aggression, leadership, and interestingly mathematical ability. When women receive testosterone in hormonal treatments, their mathematical and spatial abilities increase measurably. Estrogen, on the other hand, triggers increased sociability and empathy. Men receiving estrogen treatments sometimes find themselves crying while watching movies that would never have previously elicited such an emotional response. This suggests that there are very clear internal mechanisms that account for the differences in the sexes. These differences did not arise from nowhere; they arose because they must have conferred at direct evolutionary advantage to the human species.

In conclusion, the disparity between men and women in the sciences is a direct biological consequence that has been amplified by the socialization of women. Men have slightly higher IQs and considerably higher genetic variability. In addition, men on average have superior mathematical and spatial abilities that are due in great part to the different hormonal profiles of men and women. These biological factors are the principal contributors to the disparity. By promoting equal opportunity our society can lower the disparity, but it will be very difficult if not impossible to eradicate it completely.

Hi Michael,
Thank you for reading Nico's paper so carefully and responding so passionately.

Nico and I talk about evolutionary psychology a lot and his thinking in the field has probably been shaped a bit by mine, but I'll just try to answer for myself.

The first thing I would say is that I think Nico and I firmly agree that all human beings are irreducibly equal in a moral and spiritual sense. We are both disturbed by the high degree of social inequality that is commonly accepted in society. However, I think it is naive to believe that inequality is purely a matter of socialization.

In fact, people do have different IQs and these differences result in different social outcomes. In our society, it is broadly considered acceptable that people with very high IQs can earn much more money than people with below-average IQs. I personally question that assumption, which I think derives in part from the fact that traditions and customs are dicatated by elites, and elites owe their privileged status to special opportunities for the cognitively favored.

But it has become virtually a religious belief that differences in IQ between the genders or between races are impossible. It would in fact be nice to know that the genders and races are all on precisely equal footing when it comes to IQ, as that would make our analysis of racism and sexism a lot easier. However, what Nico and I would like you to consider, is that unfortunately the case is not as clear as one might hope. I refer you to the Wikipedia entry for Diane Halpern, former president of the American Psychological Association. You will see that people who have politics very similar to your own decided to investigate for themselves whether there was any basis for cognitive differences between men and women, and you will see that to their suprise they found that the evidence for such differences was overwhelming.

So I recommend that you first have a look at Halpern's book or various papers written by Richard Lynn.

Personally, I look at the belief that all races and genders are cognitively symmetrical to be a strange kind of fantasy. Why would we expect that humans, who vary so infinitely in our physical aspects, would somehow all be identical psychologically? It is commonly accepted that within families and within societies there are enormous differences in IQ, so why is it inconceivable that there could be differences between genders or races?

As a person of Mexican descent, I am aware of studies which suggest that Mexicans have lower IQs on average than white Americans. This does not bother me in the least. I like Mexicans and feel proud of Mexico, but I don't feel any need to boast that we are the smartest people in the world. If you spend some time in Mexico, you have to admit, we often don't organize ourselves in a very smart fashion. Despite that, I'd much rather spend a month in Mexico than in Belgium. The Belgians may have higher IQs, but their culture seems boring and stale by comparison to life in Mexico (though I do like their beer and chocolate).

I think women not only deserve as much respect as men, I think our society would be better off if more positions of authority were held by women. However, that is not incompatible with me reading the various studies which show that men have about a 4-point gap over women on IQ, and that this disparity becomes pronounced toward the high and low ends of the spectrum.

Anybody who doesn't think you need to be a bit of an idiot-savant to do graduate-level physics is almost certainly bullshitting about physics, and in fact Michael I would not be surprised if your quantum mechanics is a bit rusty. Graduate level physics is just a weirdly advanced skill and most people could never do it no matter how long they studied. Imagine a juggler who juggles a thousand balls at once, it's something like that.

It's also something that you can't talk about to normal people. No one becomes the life of the party by talking about nuclear physics research, though you can be entertaining talking about your day as a trial lawyer or pediatric surgeon, jobs where we find women well represented.

So I really think you are making a bit of a tempest in a teapot, getting all upset and offended about what is nothing more than a simple physical reality. You would never argue that all men and women are the same height and weight, because your eyes prove the opposite; the only difference with IQ studies is that you just haven't read them. Once you do, you'll have to change your argument. Have a look at Louann Brizendine's "The Female Brain," for a pop intro to the topic, she's a feminist neuroscientist who disagreed with Larry Summers, so I think you can trust her.

When you know something about the topic, love to talk with you further about it. But beware, as Nico points out, of studies that are not longitudinal enough to reveal age-differences through adulthood.

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