Abstract

Previous research has shown greater risk aversion when people make choices about lives than cash. We tested the hypothesis that compared to placebo, exogenous testosterone administration would lead to riskier choices about cash than lives, given testosterone's association with financial risk-taking and reward sensitivity. A double-blind, placebo-controlled, randomized trial was conducted to test this hypothesis (Clinical Trials Registry: NCT02734238, www.clinicaltrials.gov). We collected functional magnetic resonance imaging (fMRI) data from 50 non-obese males before and shortly after 28 days of severe exercise-and-diet-induced energy deficit, during which testosterone (200 mg testosterone enanthate per week in sesame oil) or placebo (sesame seed oil only) was administered. Because we expected circulating testosterone levels to be reduced due to severe energy deficit, testosterone administration served a restorative function to mitigate the impact of energy deficit on testosterone levels. The fMRI task involved making choices under uncertainty for lives and cash. We also manipulated whether the outcomes were presented as gains or losses. Consistent with prospect theory, we observed the reflection effect such that participants were more risk averse when outcomes were presented as gains than losses. Brain activation in the thalamus covaried with individual differences in exhibiting the reflection effect. Testosterone did not impact choice, but it increased sensitivity to negative feedback following risky choices. These results suggest that exogenous testosterone administration in the context of energy deficit can impact some aspects of risky choice, and that individual differences in the reflection effect engage a brain structure involved in processing emotion, reward and risk.