Effect Of Estrogen And testosterone On Economic Behavior [Women Only] Humans display sizeable individual variation in economic behaviors. Heterogeneity is large both in the domain of personal decision-making and in the domain of social interaction. Some individuals willingly take risks that others pay to avoid, and in situations where some individuals are altruistic and trusting, others are selfish and distrustful. Relatively little is known about the sources of such preference heterogeneity, but two recent findings suggest that biological factors are important. First, comparisons of the behavior of identical and fraternal twins indicate that genetics explains a sizeable part of the variation in preferences across a wide range of economic domains. Second, a controlled increase in the level of the mammalian hormone oxytocin causes more trusting behavior. Several studies also report that behavior is correlated with the level of sex hormones. Research finds that subjects with a higher testosterone level are more likely to reject unfair offers in the ultimatum game and finds a correlation between testosterone levels and financial risk-taking behavior. Two studies report that risk-taking behavior varies over the menstrual cycle; women are more risk averse during the ovulatory phase—that is, when the estrogen level is high. Because hormone levels in general are under strong genetic influences, these relationships between hormone levels and behavior suggest one possible channel for the intergenerational transmission of behavior. Because men and women have sharply different levels of sex hormones, it is natural to think that hormones are implied in the differences between male and female behavior. Experimental evidence shows that, on average, women tend to be more risk averse, less competitive, and more prosocial than men. Hormones affect the brain by binding to specific receptors, and previous work suggests that differences in the organization of brain areas in males and females depend on hormones. Hormones may affect cognition, mood, well-being, sexuality, and social behavior. However, the existing evidence on the relationship between sex hormones and economic behavior is merely correlative. It does not admit causal inference. To investigate whether there is a causal link, researchers conducted a double-blind randomized trial, with subjects randomly allocated to treatments with estrogen, testosterone, or placebo. The subjects were healthy postmenopausal women in the 50–65 year age group, carefully screened to rule out any contraindications to treatment. After 4 weeks of treatment, the subjects participated in a series of economic experiments with real monetary payoffs at the Karolinska University Hospital in Stockholm. To measure financial risk aversion, they elicited subjects' value of a 50/50 gamble to win Swedish Kronor (SEK) 400. This choice-based measure was complemented by two hypothetical questions used and validated —a hypothetical financial investment question (“risk investment”) and a survey question about the general willingness to take risks (“risk assessment”). They used a dictator game to measure subjects' altruism, an ultimatum game to measure their reciprocal fairness, and a trust game to measure their trust and trustworthiness. In comparison with placebo, they hypothesized that testosterone decreases risk aversion, altruism, trust, and trustworthiness and increases reciprocal fairness, and that estrogen increases risk aversion, altruism, trust, and trustworthiness and decreases reciprocal fairness. The induced changes in estrogen and testosterone levels have previously been associated with important clinical effects. Numerous studies support that estrogen therapy of this kind is effective for treatment of menopausal symptoms, such as flushing, sweating, and sleep disturbance. Furthermore, testosterone therapy resulting in similar serum levels as in this study has been shown to improve psychosexual function, e.g., arousal, desire, satisfaction, and well-being in postmenopausal women. Yet, their study offers no support for the hypothesis that sex hormones affect economic behavior. Zethraeus N, Kocoska-Maras L, Ellingsen T, von Schoultz B, Hirschberg AL, Johannesson M. A randomized trial of the effect of estrogen and testosterone on economic behavior. Proceedings of the National Academy of Sciences 2009;106(16):6535-8. A randomized trial of the effect of estrogen and testosterone on economic behavior Existing correlative evidence suggests that sex hormones may affect economic behavior such as risk taking and reciprocal fairness. To test this hypothesis we conducted a double-blind randomized study. Two-hundred healthy postmenopausal women aged 50-65 years were randomly allocated to 4 weeks of treatment with estrogen, testosterone, or placebo. At the end of the treatment period, the subjects participated in a series of economic experiments that measure altruism, reciprocal fairness, trust, trustworthiness, and risk attitudes. There was no significant effect of estrogen or testosterone on any of the studied behaviors.