Many studies show that testosterone male animals more aggressive but how the hormone affects human decision making has, surprisingly, had little attention. Keen to take a closer look, a team ran the largest human testosterone behavioural experiment ever conducted and randomly administered a single dose of either testosterone or a placebo to a sample of 243 men. They then measured the participants' performance on both the Cognitive Reflection Test, a long used exam that assesses a person's capacity to monitor their own intuitive judgments and override them when appropriate, and a mathematics test which functioned as a control.
The researchers guessed that testosterone would increase participants’ tendency to rely on their intuitive judgments, reduce inhibition of incorrect responses and thus impair their Cognitive Reflection Test performance compared to those who were given the placebo. They expected the maths test results to not be affected. This is precisely what they found. Mathematics scores from both placebo and testosterone groups were nearly identical. However, Cognitive Reflection Test scores in those dosed with testosterone were a staggering 50% those of the placebo group. You can read more in The Economist article that I wrote on this here.