Does Testosterone Affect Cognitive Reflection? Evidence From a Double-Blind, Randomized Controlled Study of 1,000 Participants

The cognitive reflection test (CRT) measures reliance on intuitive thinking versus deliberate reasoning and predicts important real-world outcomes. Prior research has suggested that testosterone administration impaired CRT performance, but follow-up studies produced null results. To provide a rigorous test, we conducted a large, preregistered, double-blind, placebo-controlled experiment, unprecedented in size, with 1,000 adult men, as part of an adversarial collaboration. Participants received a single dose of intranasal testosterone or placebo, completed the CRT, and rated their confidence level. We found an insignificant treatment effect on the CRT, with the point estimate in the opposite direction of the original hypothesis (β LOGIT = 0.118, 95% confidence interval (CI) = [−0.099, 0.335]). In a second primary test, we found a significant negative treatment effect on confidence (β LOGIT = −0.329, 95% CI = [−0.558, −0.100]), which is also the opposite of our prediction. Our findings challenge earlier claims about testosterone’s cognitive effects and highlight the importance of high-powered replications. Long-term or developmental testosterone effects remain potentially important but difficult to study.