The Imprinted Brain

How genes set the balance between autism and psychosis

Sex Differences Driven By Impulse

Men are harder on the gas, women better on the brakes.

Like it or not, there are universal differences in psychology and behavior between men and women. A recent meta-analysis by researchers at Durham University in the UK points out that men are more physically and verbally aggressive than women across data sources and nations. Men account for 76 percent of all criminal arrests in the United States, and commit 89 percent of homicides and 82 percent of all violent crime. Worldwide, men use drugs (alcohol, tobacco, cannabis, and cocaine) more than women and participate more often in extreme sports, such as sky-diving and mountain-climbing. Men are also more likely than women to suffer from a range of psychopathologies characterized by externalizing and impulsive behaviors such as antisocial personality disorder, conduct disorder, attention-deficit/hyperactivity disorder, and intermittent explosive disorder.

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But perhaps nowhere are sex differences in impulsiveness seen more graphically than on the road, where men drive more recklessly than women, are less likely to use seat-belts, and are more likely to speed, tail-gate, refuse to yield, jump lights, and drive while drunk. The result is a male accident rate three times as high as that of females in the USA and a fatality rate an order of magnitude higher (four per billion miles for a 33-year old female and 40 for a 20-year old male). Indeed, the courts find that men commit 97 percent of dangerous driving offences, 85 percent of careless driving offences, and 83 percent of speeding offences. Another result is that men—and young men driving fast cars especially—can pay up to three times the insurance premiums of women of the same age.

This is particularly interesting because driving is an evolutionarily-novel behavior which is learnt—and indeed examined—and governed by complex rules, regulations, and conventions. Behavior on the road is actively patrolled, policed, and under surveillance by society in all kinds of ways. Driving cars is found most in the most advanced industrialized societies with the greatest degree of sexual equality and can be done with equal facility by people of either sex—again, most notably where the most advanced driving technology is in use (such as automatic transmissions, powered steering, and satellite navigation). Surely, driving is one behavior where no sex differences should be found, and where modern culture, technology, and education should have made the sexes indistinguishable! Indeed, the European Union has legislated the difference away where insurance premiums are concerned by outlawing discrimination in insurance on the basis of sex.

That may solve the problem for the politicians (and add to the bonuses of the insurers if, as is likely, we all end up paying more!). But it doesn’t help if we wish to understand the issue. On the contrary, in organizing their review of the literature, the authors of this study “focused on theoretical approaches to impulsivity, highlighting the extent to which they emphasize over-attraction to reward (strong approach motivation), under-sensitivity to punishment (weak avoidance motivation), or problems with effortful or higher order control.” Reverting to driving, they point out that “these can be thought of as a problem with a stuck accelerator, a problem of faulty brakes, or a problem of poor judgment by the driver.”

Drawing on evolutionary, criminological, developmental, and personality theories, the authors predicted that sex differences would be most pronounced in risky activities, with men demonstrating greater sensation-seeking, greater sensitivity to reward, and lower sensitivity to punishment, but with a female advantage in effortful-control. They analyzed 741 effect sizes from 277 studies, including psychometric and behavioral measures. Women were consistently more sensitive to punishment, but men did not show greater sensitivity to reward. Men did show significantly higher sensation-seeking on questionnaire measures and on a behavioral risk-taking task. Questionnaire measures of deficits in effortful-control showed a very modest effect size in the male direction as predicted, but sex differences were not found on delay-discounting or executive function tasks.

The study concludes that “the results indicate a stronger sex difference in motivational rather than effortful or executive forms of behavior control. Specifically, they support evolutionary and biological theories of risk taking predicated on sex differences in punishment sensitivity.” Reverting to driving again, you might say that men are heavier on the accelerator, but that women are more likely to brake and have marginally better judgment than men in some respects, but not all.

The legislation of sex differences out of existence where drivers’ insurance is concerned is a telling example of modern, PC prudery about sex-as-psychology-and-behavior which I discussed in general terms before. And as I have also pointed out before, the fundamental evolutionary and genetic insight of modern, "selfish gene" Darwinism is that, thanks to sex, genes from both male fathers and female mothers have to co-exist in individuals of both sexes and can often be in conflict, in fact over what sex the individual should be, and in principle even over how to drive a car. Today we know that genes from mothers and fathers can be differentially expressed and can build different parts of the brain and thereby be responsibe for different aspects of behavior. Indeed, according to the imprinted brain theory, such differential expression of parental and sex chromosome genes explains much of mental illness and normality alike.

Overall, typical sex differences will of course result, but their evolutionary, psychological, and genetic basis will be found to be much less obvious than they seem; and future research of the kind flagged up here will doubtless reveal it even more clearly. Indeed, the authors conclude that “A clearer understanding of sex differences in impulsivity depends upon recognizing important distinctions between sensation-seeking and impulsivity, between executive and effortful forms of control, and between impulsivity as a deficit and as a trait.”

 

(With thanks to Anne Campbell for bringing this to my attention. See her A Mind of Her Own: The Evolutionary Psychology of Women, for more on this subject.)

Christopher Robert Badcock, Ph.D., is author of The Imprinted Brain: how genes set the balance between autism and psychosis. 

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