Hotheaded, driven, impulsive — that’s Holywood’s archetypical main action movie dude. But there might be a kernel of truth to this over-the-top silver screen persona, as a new paper reports on the effects of testosterone on behavior.


Image credits Chris & Karen Highland / Flickr.

Now, I don’t often partake into the habit of generalizing behavior by gender — men like to keep an open mind, after all. But I think we can all agree that (to some extent) if something seems fun, bragworthy, or will impress someone but isn’t exactly sensible, there’s one guy close at hand ready to take up the challenge. We’re also the half of the table more likely to jump into a pub melee and/or send you a lot of texts with the word “duck” autocorrected in afterward. In short, men are on often regarded as the less restrained, more aggressive, more impulsive of the sexes.

A team of researchers from Caltech, the Wharton School, Western University, and ZRT Laboratory set out to see if men’s higher levels of sex-hormone testosterone can explain this tendency to rely on intuitive judgements at the expense of cognitive reflection — the self-scrutinizing process by which someone stops to consider if these gut reactions actually make sense. They report that men given doses of the hormone performed worse on a test designed to measure levels of cognitive reflection compared to their counterparts who received a placebo.


The study included 243 male testees and was the largest ever conducted of its type. Participants were randomly assigned to receive a dose of either testosterone or placebo gels before the test began. They were also evaluated on their motivation levels, engagement with the test, and basic math skills before the tasks through a simple test.

The questions generally involved or required math to solve. They weren’t particularly hard, but they were designed in such a way as to seem really simple and elicit a ‘gut’ solution. For example, take the following task: If a bat and a ball cost $1.10 in total, and the bat costs $1 more than the ball, how much does the ball cost?

Not exactly rocket science™, is it? The trick is that for most people, our brains blurt out “10 cents” before we get a chance to think about it. This answer is incorrect because then the bat would only be 90 cents more expensive than the ball. If you go through the mental process of evaluating your result, you’ll conclude that the ball, in fact, costs 5 cents and the bat $1.05. But a person who relies on their gut instinct is more likely to answer “10 cents” without going through cognitive reflection, giving the team a good indication of how often someone just goes with their instincts vs how often they check the validity of their intuition.

The participants could take as much time as they wanted on the test and were offered $1 for each correct answer and an additional $2 if they answered all the questions correctly as an incentive.

“What we found was the testosterone group was quicker to make snap judgments on brain teasers where your initial guess is usually wrong,” says Colin Camerer, Caltech’s Robert Kirby Professor of Behavioral Economics and Chair of the T&C Chen Center for Social and Decision Neuroscience Leadership. “The testosterone is either inhibiting the process of mentally checking your work or increasing the intuitive feeling that ‘I’m definitely right.'”

The testosterone group scored significantly lower than their placebo counterparts, answering 20% fewer questions correctly, on average. They were also quicker to give incorrect answers and gave “correct answers more slowly than the placebo group,” the authors note. This effect wasn’t seen in the results of the initial math test, showing a “clear and robust causal effect of [testosterone] on human cognition and decision-making,” the team concludes.

They believe this cognitive shift stems from testosterone’s documented effect of increasing confidence levels. The hormone is also believed to enhance the male drive for higher social status, and higher levels of confidence enhance status, the authors write.

“We think it works through confidence enhancement. If you’re more confident, you’ll feel like you’re right and will not have enough self-doubt to correct mistakes,” Camerer says.

The results should raise questions about the negative effects testosterone-replacement therapy might incur, he adds. The practice is aimed at reversing the decline in sex drive experienced by many middle-aged men, but in light of the new findings, it’s likely that their behavior and decision-making processes also change following the procedure.

The paper “Single dose testosterone administration impairs cognitive reflection in men” has been published in the journal Psychological Science.

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