A new and extensive study challenges the widely held belief that the hormone testosterone influences men’s economic choices, such as their willingness to take risks or act generously. The research, the largest of its kind, found that men who received a dose of testosterone made the same economic decisions as men who received a placebo. The findings were published in the Proceedings of the National Academy of Sciences.
Testosterone is a hormone primarily associated with the male reproductive system, though it is also present in women at lower levels. It is known to play a role in the development of male physical characteristics like muscle mass and a deeper voice. For years, scientists have also explored potential links between testosterone and behaviors like aggression, dominance, and competition. This led to an expansion of research into the hormone’s possible effects on economic preferences, which are the individual tendencies that guide people’s choices about money and resources.
The idea that a hormone linked to masculinity and dominance might also shape financial risk-taking or competitive drive was an intuitive one. However, the scientific literature on this topic has been filled with conflicting results. Some smaller studies suggested testosterone increased risk-taking, while others found no effect or even opposite effects.
Many of these prior experiments involved small numbers of participants and were not preregistered, meaning the plan for analyzing the data was not publicly declared beforehand. This left open the possibility that the reported findings could be false positives. Anna Dreber, a professor at the Stockholm School of Economics in Sweden, and a large team of international collaborators conducted this new study to provide more reliable evidence using a large sample and a preregistered design.
To investigate the hormone’s effects, the researchers recruited 1,000 healthy men between the ages of 18 and 45. The study used a double-blind, randomized controlled design, which is considered a gold standard in experimental research. This means that neither the participants nor the researchers interacting with them knew who was receiving the active treatment. Half of the men were randomly assigned to self-administer an 11-milligram dose of testosterone gel through the nose, while the other half received an identical-looking placebo gel. After a 30-minute absorption period, during which testosterone levels were expected to peak, the participants completed a series of computer-based tasks designed to measure different economic behaviors.
The tasks included a variety of well-established economic games. To measure risk preferences, participants made a series of choices between a guaranteed amount of money and a lottery with uncertain outcomes. Their decisions were used to calculate their levels of risk aversion, which is a preference for a certain outcome over a risky one, and loss aversion, the tendency for the pain of losing to be psychologically more powerful than the pleasure of gaining.
Social preferences were measured using several games. In the ultimatum game, one participant, the proposer, had to offer a split of $10 to a second participant, the responder. If the responder accepted the offer, the money was divided as proposed. If the responder rejected it, both players received nothing. This game measures fairness, as proposers often make generous offers to avoid rejection, and responders may punish offers they perceive as unfair.
Another task was the trust game, where an investor could send a portion of their $10 to a trustee. The amount sent was tripled, and the trustee then decided how much of that larger sum to return to the investor. The amount sent by the investor is considered a measure of trust, while the amount returned by the trustee is a measure of trustworthiness. Generosity was assessed with the dictator game, in which a participant simply decided how much of a $10 endowment to give to another person who had no say in the matter.
Finally, the experiment measured the men’s willingness to compete. Participants first solved math problems and were paid based on how many they got right. They then performed the task again under competitive conditions. In the final stage, they could choose whether they wanted to be paid based on their own performance or to enter a competition where they would earn more if they outperformed an opponent.
After collecting all the data, the researchers analyzed the choices made by the men in the testosterone group and compared them to the choices of those in the placebo group. The results were clear and consistent across all measures. The study found no evidence that the testosterone treatment had any effect on any of the nine primary outcomes. Men who received testosterone did not take more risks, reject more unfair offers, show less trust, act less generously, or choose to compete more often than men who received the placebo.
The researchers also examined the relationship between the men’s natural baseline levels of testosterone, measured in saliva samples taken before the gel was administered, and their economic choices. Once again, they found no strong evidence of an association between a man’s existing testosterone levels and his behavior in the economic games.
“Earlier studies, often based on small samples, suggested that testosterone might impact our willingness to take risk or compete in economic settings,” Dreber explained. “But in this substantially larger experiment where we have also preregistered how we would do the analysis prior to observing the data to avoid bias, we do not find any effects of testosterone on economic decision making. Our findings give us strong evidence that short-term testosterone boosts don’t meaningfully change men’s economic choices.”
“This study is significant because it directly challenges the narrative that short-term fluctuations in testosterone explain why some people take bigger economic risks, reject unfair deals, or act more competitively in life,” said co-lead author Justin M. Carré, a professor at the Faculty of Arts and Science at Nipissing University in Canada.
“Our findings underscore the value of replication with larger samples and preregistered designs. Findings reported from small experiments can vanish when tested more rigorously,” added co-lead author Magnus Johannesson, a professor at the Department of Economics at the Stockholm School of Economics.
The authors acknowledge certain limitations of their study. Their findings are specific to the effects of a single, short-term dose of testosterone in men and cannot be generalized to women, who may respond differently to the hormone. It is also possible that different dosages, administration methods, or longer time periods between administration and testing could produce different results.
The study only examined the immediate effects of a temporary rise in testosterone. It does not speak to the potential long-term effects of testosterone exposure or its influence during critical developmental periods, such as puberty. Investigating these long-term or developmental effects in humans through experiments is ethically challenging.
However, the study’s null findings on the link between natural baseline testosterone and behavior are consistent with the experimental results. The study stands as a powerful conceptual replication attempt that fails to support a number of previously published, high-impact findings, suggesting that the role of short-term testosterone fluctuations in adult male economic behavior may be far smaller than previously thought.
The study, “Investigating the effects of single-dose intranasal testosterone on economic preferences in a large randomized trial of men,” was authored by Anna Dreber, Magnus Johannesson, Gideon Nave, Coren L. Apicella, Shawn N. Geniole, Taisuke Imai, Erik L. Knight, Dylan Manfredi, Pranjal H. Mehta, Valentina Proietti, Steven J. Stanton, Alina Zeltikova, Francesca R. Luberti, Triana Ortiz, and Justin M. Carré.