Combining Behavioral Endocrinology and Experimental Economics: Testosterone and Social Decision Making

Summary

The procedure described in this protocol shows that testosterone administration and folk beliefs about testosterone may be associated with directly opposed social behaviors.

Abstract

Behavioral endocrinological research in humans as well as in animals suggests that testosterone plays a key role in social interactions. Studies in rodents have shown a direct link between testosterone and aggressive behavior¹ and folk wisdom adapts these findings to humans, suggesting that testosterone induces antisocial, egoistic or even aggressive behavior². However, many researchers doubt a direct testosterone-aggression link in humans, arguing instead that testosterone is primarily involved in status-related behavior^3,4. As a high status can also be achieved by aggressive and antisocial means it can be difficult to distinguish between anti-social and status seeking behavior.

We therefore set up an experimental environment, in which status can only be achieved by prosocial means. In a double-blind and placebo-controlled experiment, we administered a single sublingual dose of 0.5 mg of testosterone (with a hydroxypropyl-β-cyclodextrin carrier) to 121 women and investigated their social interaction behavior in an economic bargaining paradigm. Real monetary incentives are at stake in this paradigm; every player A receives a certain amount of money and has to make an offer to another player B on how to share the money. If B accepts, she gets what was offered and player A keeps the rest. If B refuses the offer, nobody gets anything. A status seeking player A is expected to avoid being rejected by behaving in a prosocial way, i.e. by making higher offers.

The results show that if expectations about the hormone are controlled for, testosterone administration leads to a significant increase in fair bargaining offers compared to placebo. The role of expectations is reflected in the fact that subjects who report that they believe to have received testosterone make lower offers than those who say they believe that they were treated with a placebo. These findings suggest that the experimental economics approach is sensitive for detecting neurobiological effects as subtle as those achieved by administration of hormones. Moreover, the findings point towards the importance of both psychosocial as well as neuroendocrine factors in determining the influence of testosterone on human social behavior.

Protocol

1. Subject Recruitment

1. Subjects are recruited via an on-line database⁵ containing a list of about 3000 student volunteers. From this list we only contact women who have not previously participated in similar studies and ask them whether they are interested in participating in this study. We invite exclusively women as the time course of neurophysiological effects after acute testosterone administration is well established among women^6,7. For men, this time course is not yet very well understood.
2. The interested subjects are then screened in a telephone interview to exclude medication intake, somatic diseases, hormonal contra....

Discussion

An indication that your results are valid is if the average offers observed is similar to what other studies found. Typically, average offers are between 30 - 40% of the total amount and approximately half of the subjects offer the equal share¹⁴. On the other hand, a likely indicator that subjects did not understand the rules of the game is if offers of more than 50% are observed. It is worth noting, however, that there is considerable heterogeneity in the distribution and average offers observed in studies ar.......