Are boys more aggressive than girls?

August 9, 2010

In this post I’ll excerpt the portions of Lise Eliot’s Sci Am Mind article having to do with physical activity levels and aggression in boys and girls.

Boys are more physically active than girls, in infancy and throughout childhood. They kick, swing their arms and race around the house noticeably more than girls do, as many exhausted parents can testify. The difference may emerge before birth, although not every ultrasound study finds a sex difference in fetal movement. Nevertheless, the disparity is clear during the first year and expands through childhood, according to a 1986 analysis [possibly this?] of more than 100 studies by psychologist Warren Eaton and his colleagues at the University of Manitoba in Canada, which reveals that the average boy is more active than about 69 percent of girls.

That gap is statistically moderate, larger than differences in verbal and math skills but small enough to permit many exceptions to the rule, notably the 31 percent of girls who are more active than the average boy. Sex hormones — in particular, a relative abundance of testosterone in the womb — appear to trigger boys’ fidgetiness. And yet the sex difference in physical activity continues to widen during childhood, despite the fact that sex hormone levels do not differ between boys and girls from six months of age to puberty. Parenting is likely one factor amplifying the disparity. Mothers discourage physical risk taking more in daughters than in sons, suggest studies in the laboratory and on playgrounds. […] Peers also push conformity: in their preferred all-boy groups, energetic boys feed off one another, whereas energetic girls tend to settle down in clusters of more docile friends. In organized sports, girls start playing at a later age, quit earlier and join fewer teams overall than boys — differences that are influenced by parents and peers.

Here’s a Warren Eaton paper arguing that some but not all of the sex difference in motor activity results from girls maturing faster than boys.

Boys are more physically aggressive than girls, according to many studies, including a 2004 analysis [pdf] by psychologist John Archer of the University of Central Lancashire in England. That difference is linked to prenatal testosterone but not, surprisingly, to the resurgence in boys’ testosterone level in adolescence, because boys do not suddenly become more aggressive when they go through puberty, as Archer’s work also indicates. Nor is this sex difference absolute. Two- and three-year-old girls, for instance, frequently kick, bite and hit other people — not quite as much as toddler boys but about three times more than either sex does later in childhood. In addition, girls fight with indirect, or relational, aggression. Through gossip, ostracism, whispers and, most recently, harassing text messages, girls leave more scars on competitors’ psyches than on their bodies. […]

Thus, both sexes compete and both sexes fight; what differs is the degree to which such behavior is overt or hidden. Because physical aggression is a much greater taboo for girls than boys, they learn, even early in elementary school, to keep it below the surface, in the eye rolling and best-friend wars that teachers rarely notice and are harder to police.

Here’s a 1994 paper arguing it’s nonsensical to claim that males are more aggressive than females. Aggression is strategic. “Since females are physically weaker than males, they may early in life learn to avoid physical aggression, and instead develop other means [i.e., verbal]. Choice of aggressive strategy may become partly habitual, and also reinforced by social norms in the society in question.”

Next time: where do toy preferences come from?


4 Responses to “Are boys more aggressive than girls?”

  1. Intriguing. Some of these arguments seem perverse to me at first glance, but that’s part of what makes them interesting. Some of them also seem to me be reaching a bit. But that’s just my first impression, not meant to be any sort of counter-argument.

    My initial thought regarding aggression is that these arguments are not defining terms the same way as biologists do, or the way psychologists do who think like Pinker (those with a biological spin).

    For example it would be difficult to find a serious claim to the effect that women can’t possibly become as aggressive as men under extreme conditions, but that feels to me like what the underlying agenda seems to be here, to argue against the notion that men are somehow “essentially” more aggressive. But no modern scientific theory makes that hypothesis.

    The more realistic claim is that under a wide range of developmental and environmental conditions, human males become more aggressive in general, defined in the behavioral manner that we use to describe aggression in other species.

    That wide range of developmental and environmental conditions includes much of what we do in parenting, they are not somehow excluded just because they play a role in culture. Culture is constrained to some degree by who we are and what our basic needs and abilities are (cultures have to meet biological needs in some sense, they are not entirely random ideas and behaviors and artifacts), something that seems fairly obvious to me but for some reason ends up being seen as unreasonable in some circles.

    I am not really hearing arguments against the biological theory of male aggression, I am hearing arguments saying that we tend to raise boys as more aggressive or that claiming men to be more aggressive than women is “nonsense,” both of which seem like largely orthogonal postures to the biological notion of sex differences in aggression or causal models relevant to it.

    Just some thoughts, I hope they aren’t too far afield. I’m enjoying your thoughts here.

  2. JR Minkel Says:

    This post was a little sketchy, I grant you. Regarding how we define aggression per se, I don’t think we’re directly comparable with other animals. Office politics can get very aggressive without being at all physical. I’m not sure there’s any analogue for that in the animal kingdom outside of social primates. That’s what I meant when I said aggression is strategic. Our minds allow us to evaluate the costs and benefits of an aggressive act based on the situation, which includes our own physical capacities. Men are physically bigger than women and are encouraged to express aggression physically e.g. through competitive sports. So it makes sense to think our cultural environment would produce different patterns of aggression in men and women. Focusing on a hypothetical biological component to male aggression misses the point that social science should be an agent for positive social change.

  3. Yes, I think we agree, people in different sciences are focusing on different things and defining terms differently for different purposes. I tend to agree with Pinker to some degree that social sciences have traditionally gone overboard in ignoring biology completely, but the opposite mistake is not uncommon either I think, applying too simplistic a biological explanation to social science.

    We are first and foremost part of the nature rather than apart from it, but that doesn’t mean we completely understand nature.

    As to the “purpose” of a given science, for me personally if it is something other than understanding the underlying phenomena, then I feel as if we are sliding at that point into the realm of political argument and it becomes a somewhat different discussion, one loaded more with values and preferences.



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