#dual process

The sex steroid testosterone regulates reproductive behaviors such as intra-male fighting and mating in non-humans. Correlational studies have linked testosterone with aggression and disorders associated with poor impulse control, but the neuropsychological processes at work are poorly understood. Building on a dual-process framework, we propose a mechanism underlying testosterone’s behavioral effects in humans: reducing cognitive reflection. In the largest behavioral testosterone administration study to date, 243 men received either testosterone or placebo and took the Cognitive Reflection Test (CRT), that estimated their capacity to override incorrect intuitive judgments with deliberate correct responses. Testosterone administration reduced CRT scores. The effect was robust to controlling for age, mood, math skills, treatment expectancy and 14 other hormones, and held for each of the CRT questions in isolation. Our findings suggest a mechanism underlying testosterone’s diverse effects on humans’ judgments and decision-making, and provide novel, clear and testable predictions.