

"The world needs less testosterone."

I can't begin to count how many times I've heard this cliché. How many times I've nodded in sympathetic agreement, joined in a good tsk tsk at the horror of it all. These men and their big, fat, world-destroying, testosterone-fuelled antics: the fights, the fraud, the fury.

Then, I (recently) attended a conference on the evolution of violence, and a speaker (Dr T) indulged, citing mammalian aggression to be the result of 'testosterone-poisoning'. Admittedly a bit hyperbolic. And admittedly a bit... well, wrong.

Time to duel. First, of course, some entertainment, courtesy of National Geographic.

So, if we're so sure the world needs less of this testosterone thing, what is it? What does it do to your mind? Why are those rugby players so ugly?

Spoiler alert: no one really knows, but we all pretend to. (Especially about the last question.)



THE FACTS: Behavioural research on testosterone is, if anything, inconsistent. Highly inconsistent. And a bit surprising too. Some studies found that high pre-natal exposure to testosterone leads to more generous game offers in men and women (a.k.a charity). Others have concluded that, when testosterone is artificially enhanced, men become less generous, more vengeful and antisocial. Yet others still have suggested that hypogonadal males (a.k.a low testosterone-producing males) who had their testosterone increased saw no jump in aggressive behaviour, and in fact became more friendly, energetic and, well, happy.

Words/phrases that are thrown around a lot in testosterone studies: cortisol, orbitofrontal cortex, amygdala, oxytocin -- the list goes on. The point? We don't really know how (or even if) testosterone makes humans more aggressive. We can't isolate it. And it seems that it may just be peripheral to other hormones in aggressive, status-seeking, high-libido and/or antisocial behaviour.

I recently ear-marked this study, which found that increased levels of testosterone induce aggressive behaviour ONLY when there is perceived unfairness in a bargaining situation. It's the system (not the hormone), stupid.

But my all-time favourite is this Nature letter, where the reality and 'folk wisdom' of testosterone's effects were teased out in a neat experiment. In a game situation, researchers gave a single dose of testosterone to certain women, the rest were given a placebo. Some had been told that they were receiving testosterone (even if they were the placebo group) while others, who had been told nothing, were actually administered testosterone. The result: the women who had received testosterone without knowing became fairer, more generous and had increased efficiency in social interactions, while the other group (those who had been told that they were receiving testosterone) behaved much more unfairly. In sum: one group acted they way they thought testosterone should affect humans (and it wasn't pretty). But the reality was much different. Case and point, ladies and gentlemen.

Testosterone may in fact be the key to aggressive mammal behaviour. It may also be the fountain of life. Who knows. But the strongest (and perhaps only) current link between testosterone and human aggression is implicit cultural assumption. And what's implicit and not explicit is too often wrong.

Time to give your gonads some credit, Dr T.

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