The always fascinating Ed Yong, over at Not Exactly Rocket Science, highlights a recent study on testosterone, aggression and the placebo effect.
If ever a hormone was the subject of clichés and stereotypes, it is testosterone. In pop culture, it has become synonymous with masculinity, although women are subject to its influence too. Injections of testosterone can make lab rats more aggressive, and this link is widely applied to humans. The media portrays “testosterone-charged” people as sex-crazed and financially flippant and the apparent link with violence is so pervasive that the use of steroids has even been used as a legal defence in a US court.
Christoph Eisenegger from the University of Zurich tested this folk wisdom by enrolling 60 women in a double-blind randomised controlled trial. They were randomly given either a 0.5 milligram drop of testosterone or a placebo. He only recruited women because previous research shows exactly how much testosterone you need to have an effect, and how long it takes to do so. We don’t know that for men.
The women couldn’t have known which substance they were given, but Eisenegger asked them to guess anyway. Their answers confirmed that they couldn’t tell the difference between the two drops. But they would also confirm something more startling by the trial’s end.
Each woman was paired with a partner (from another group of 60) and played an “Ultimatum game” for a pot of ten Swiss francs. One woman, the “proposer”, decided how to allocate it and her partner, “the responder” could choose to accept or refuse the offer. If she accepts, the money is split as suggested and if she refuses, both players go empty-handed. The fairest split would be an equal one but from the responder’s point of view, any money would be better than nothing. The game rarely plays out like that though – so disgusted are humans with unfairness that responders tend to reject low offers, sacrificing their own meagre gains to spite their proposers.
Overall, Eisenegger found that women under the influence of testosterone actually offered more money to their partners than those who received the placebo. The effect was statistically significant and it’s exactly the opposite of the selfish, risk-taking, antagonistic behaviour that stereotypes would have us predict.
Those behaviours only surfaced if women thought they had been given testosterone. Those women made lower offers than their peers who believed they had tasted a placebo, regardless of which drop they had been given. The amazing thing is that this negative ‘imagined’ effect actually outweighed the positive ‘real’ one. On average, a drop of testosterone increased a proposer’s offer by 0.6 units, but belief in the hormone’s effects reduced the offer by 0.9 units.
The larger point is that our beliefs about biology – those stupid cliches about sex hormones, for instance – often overwhelm the actual effects of biology. Thanks to some evolutionary innovations (like that overhang of brain called the prefrontal cortex), we’re able to suppress our aggressive feelings and turn off our anger. We can resist even the most primal urges. And yet, all it takes is a whiff of imaginary testosterone before we start behaving like selfish hominids, imitating what we assume is our “natural” state.
Here’s a question: does all this new knowledge about the brain undermine our natural ability to restrain ourselves? Have we become prisoners of incomplete science? When we learn that the amygdala is an ancient part of human nature, pumping out fear and anger, does that make it harder to resist the amygdala? When we learn that sugar activates the same dopaminergic areas as sex and crack, does that make it harder to not eat the candy bar? The brain has preserved a small space for executive control, which is a weak synonym for free will. Is modern neuroscience, by describing the determinism of the fleshy machine, undermining that sense of control? My worry is that we’ve come to see our imperfections as inevitable, just like those testosterone fueled subjects acting greedy in the ultimatum game.