No brain operates in a vacuum. Our social and physical environments unconsciously shape our behaviour. The wealth of information streaming into the brain influences the likelihood of pro- or antisocial acts. You cannot distinguish between aspects of a behaviour that are “biological” and those that would be described as, say, “psychological” or “cultural.” For example, there is one hormone that is commonly tied to aggression, namely testosterone but it is far less relevant to aggression than is usually assumed.
Do differences in testosterone levels among individuals predict who will be aggressive? Initially the answer seemed to be yes but after extensive investigation, scientists conclude that the brain doesn’t pay attention to fluctuations of testosterone levels within the normal range. When there are higher than normal levels – eg. athletes and bodybuilders using anabolic steroids - risk of aggression does increase. Aggression is typically more about social learning than about testosterone.
Testosterone does subtle things to behaviour. It makes people less adept at identifying emotions by looking at people’s eyes. It also increases confidence and optimism, while decreasing fear and anxiety. But it makes people overconfident and overly optimistic, with bad consequences. In one study, testosterone made subjects more likely to think their opinion was correct and to ignore input from their partner. It makes people cocky, egocentric, and narcissistic and boosts impulsivity and risk taking, making people do the easier thing when it’s the stupid thing to do.
What is important to note is that testosterone’s effects are hugely context dependent. This context dependency means that rather than causing X, testosterone amplifies the power of something else to cause X. It does not create new social patterns of aggression; it exaggerates pre-existing ones. A person being aggressive in the future depends less on testosterone and more on social learning.
Testosterone rises in humans in both individual and team sports competition, including basketball, wrestling, tennis, rugby, and judo. There’s generally a rise in anticipation of the event and a larger one afterward, especially among winners. What is even more interesting is that watching your favourite team win raises testosterone levels, showing that the rise is less about muscle activity than about the psychology of dominance, identification, and self-esteem.
When testosterone rises after a challenge, it doesn’t prompt aggression. Instead it prompts whatever behaviours are needed to maintain status. What happens if defending your status requires you to be nice? This was explored in a study at the University of Zurich. Participants played the Ultimatum Game where you decide how to split money between you and another player. The other person can accept the split or reject it, in which case neither of you gets anything.
Prior research had shown that when someone’s offer is rejected, they feel rejected and subordinated, especially if news of that carries into future rounds with other players. In other words, in this scenario, status and reputation rest on being fair. And what happens when subjects were given testosterone beforehand? People made more generous offers. What the hormone makes you do depends on what counts as good reputation. This indicates that testosterone is sensitive to social learning.
The study contained a important additional finding that further separated testosterone myth from reality. The subjects got either testosterone or saline, without knowing which. Subjects who believed it was testosterone (independent of whether it actually was) made less generous offers. So, testosterone doesn’t necessarily make you behave in a disagreeable manner, but believing that it does and that you have got it rather than saline makes you behave in a disagreeable manner.
Additional studies show that testosterone promotes pro-sociality in the right setting. In one, under circumstances where someone’s sense of pride is dependant on honesty, testosterone decreased men’s cheating in a game. In another, subjects decided how much of a sum of money they would keep and how much they would publicly contribute to a common pool shared by all the players; testosterone made most subjects more prosocial.
What does this mean? Testosterone makes us more willing to do what it takes to attain and maintain status. And the key point is 'what it takes'. Engineer social circumstances right, and boosting testosterone levels during a challenge would make people compete like crazy to do the most acts of random kindness. In our world riddled with male violence, the problem isn’t that testosterone can increase levels of aggression. The problem is the frequency with which we reward aggression. In Behave, Robert Sapolsky writes:
. . there are few clear-cut causal agents, so don’t count on there being the brain region, the neurotransmitter, the gene, the cultural influence, or the single anything that explains a behaviour. Instead of causes, biology is repeatedly about propensities, potentials, vulnerabilities, predispositions, proclivities, interactions, modulations, contingencies, if/then clauses, context dependencies, exacerbation or diminution of preexisting tendencies.'