Are boys genetically predisposed to behavioural problems? [excerpt]

Are boys naturally more aggressive or is that just a social construct by society? Can so-called “macho behavior” be unlearned or is it intrinsic? This International Men’s Day, authors Daniel Freeman and Jason Freeman seek out those answers and more in the below excerpt from The Stressed Sex: Uncovering the Truth About Men, Women, and Mental Health.

Are boys genetically vulnerable to behavioural problems? The evidence suggests not: the relative contributions of genes and environment are on the whole very similar for males and females. That’s the broad picture, but within it may lurk some interesting details. For example, as with many other disorders, exactly which of the two factors is more influential in antisocial behaviour can vary according to age: at a particular point in life, environment has a more significant effect, while at another, genes are more decisive.

There’s some indication that this age-related pattern may be different in the sexes. It has also been suggested that the genes involved in these disorders may not be the same for men and women. But this is currently little more than a tantalizing hypothesis. Finally, some research has indicated that male antisocial behaviour may be partly influenced by a gene × environment interaction. Specifically: men who possess a variant form of a sex-linked gene (MAO-A), and who have been mistreated during childhood, may be more prone to conduct problems than those with either the gene or the maltreatment alone. Whether or not this is a factor in female antisocial behaviour is unclear. And matters are complicated by the fact that in sex-linked genes like MAO-A, men and women can have differing variant forms, meaning that it’s tricky to compare their effect across gender. The picture is clearer (fortunately) with temperament. Psychologists use the term to refer to a child’s personality and, as most parents will tell you, it seems to be largely innate. Now there’s good evidence to suggest that boys and girls vary in certain aspects of temperament.

In a meta-analysis of 189 studies covering children aged from three months to 13 years, Nicole Else-Quest and colleagues at the University of Wisconsin-Madison found that, although overall differences between boys and girls were small, there were some striking exceptions. Boys scored relatively highly for what’s known as ‘surgency’: they were active, impulsive, sociable, and enthusiastic, with a liking for rough-and-tumble play. (We might think of surgency as the ‘puppy’ ratio.) Girls, on the other hand, proved much better at ‘effortful control’: they were persistent, adept at concentrating on a given task, and able to resist acting on impulse.

We can’t simply equate surgency with antisocial behaviour, of course. But one can imagine how a combination of high energy and relatively low emotional control could help lead to problems. And Else-Quest’s findings do chime with evidence that boys are generally more physically aggressive than girls. One can detect the difference in children as young as one. For example, from about the age of 12 months boys show a willingness to use force against their peers in order to get what they want.

We get a sense of these behavioural differences between boys and girls in an experiment led by Claire Hughes, a professor of developmental psychology at Cambridge University’s Centre for Family Research. Hughes and colleagues asked 800 five-year-olds to take part in a game of SNAP!, using cards that depicted farm animals. (Tempting though it is to imagine all these children playing simultaneously—what a game that would be—in fact they did so in same-sex pairs while being supervised by a researcher.) The game was videotaped so that the researchers could study the children’s behaviour. And both parents and teachers completed a questionnaire designed to assess whether the child was prone to externalizing problems such as disobedience, aggression, and antisocial behaviour.

As you might guess, this was no ordinary game: the cards were rigged. Each child would experience both a winning and a losing streak. But though every child was confronted with the frustration of seeing their opponent winning card after card, how they reacted depended on their gender. Boys were much more likely than girls to become disruptive, for example by trying to snatch the cards, storming out, or being verbally aggressive. Predictably, the children most given to externalizing problems in general were also the most disruptive during the game—and again these were predominately boys.

What Hughes and colleagues found in the SNAP! experiment corroborates the theory that boys are more likely to indulge in externalizing behaviour than girls and, when the red mists descend, are less able to control themselves. It’s a combination that makes them especially vulnerable to conduct problems. But, in humans at least, the relationship between testosterone and aggression isn’t nearly as straightforward as the media often suggest. For example, once boys and girls reach about three to six months of age, the level of testosterone in their bodies is quite similar, and it stays that way until puberty when, of course, boys experience a huge surge of the stuff. (Yes, male sex hormones are found in females, just as female hormones are present in males.) So current testosterone levels can’t explain why pre-teen boys are typically more aggressive than pre-teen girls. Even in adolescent and adult males, the link between testosterone and aggression is quite modest. Inject young men with testosterone, as some scientists have done, and they don’t suddenly metamorphose into Incredible Hulk-type creatures, roaring and brawling and breaking the furniture. Contrary to what we might expect, the extra testosterone doesn’t in fact make them any more aggressive.

All of which suggests that simply blaming testosterone for male conduct problems is far too simplistic. Instead, we need to be much more nuanced, recognizing that the hormone seems to produce different effects at different stages of life: prenatal, postnatal, and during adolescence. And remembering too that testosterone probably affects males and females in different ways.

Featured image credit: “boy-teen-schoolboy-angry-bit” by AnnaKovalchuk. CC0 public domain via Pixabay.