Over the past several years, much has been made of the psychological influences of the hormone Oxytocin on behavior. It has been called the love hormone and the trust hormone. And there are some findings out there to support that increases in oxytocin levels can increase positive thoughts toward a partner and trust in some cases.
In that same time period, there has been much less discussion of the influence of testosterone on social relationships. This topic is explored in a paper by Maarten Boksem, Pranjal Mehta, Bram Van den Bergh, Veerle van Son, Stefan Trautann, Karin Roelofs, Ale Smidts, and Alan Sanfey in the November, 2013 issue of Psychological Science.
In this paper, participants were women who were either given a dose of testosterone or a placebo. Women were used, because men’s level of testosterone fluctuates significantly throughout the day. The testing was done about 4 hours after the administration of the testosterone, because previous studies suggest that the strongest influence of testosterone on behavior occurs about 4 hours after the testosterone is released into the bloodstream.
Participants played two economic games. In the first, they were given 20 Euros, and were told that they were playing with a partner. They could give as much of that 20€ to the other participant. The experimenter would then triple the donation, and the partner could return as much of that amount as they chose to the original donor. For example, if the participant gave 10€ to the partner, the partner would get 30€, which they could split ay way they like with the participant. This game is a measure of trust, because the participant has to trust that they will get back from the other player at least as much as they gave up.
After playing one round of this trust game participants were then told that they were playing the other side of the game. Now, they were given 60€, with the explanation that the other player had given their full 20€, and were asked how much they wanted to return to the other player. This game is a measure of how much people are willing to reciprocate in social situations.
The trust game results suggest that testosterone decreases trust. Participants gave about 54% of their money to their partner when they received the placebo, but gave only about 38% of their money when they received testosterone.
The reciprocation game suggests that testosterone increases reciprocation. Participants returned only about 43% of the money when given the placebo, but returned about 53% of the money when given testosterone.
Other measures taken during this study suggest that testosterone did not make participants more tolerant of risky options or more tolerant of ambiguous situations.
What does all of this mean?
The finding that testosterone decreases trust is consistent with a lot of work that suggests that testosterone makes people vigilant for violations that may disrupt a person’s social standing.
The reciprocation effects are interesting, though. When a person reciprocates in a game like this, they are sending a signal that they can be relied on in social situations. When people can be relied upon, that generally increases their social standing. So, testosterone may be helping people to act in a way that improves their social position.
Of course, the doses of testosterone used in this study are much higher than what women will naturally experience. Further research needs to explore whether similar effects can be obtained with testosterone levels that are similar to those that occur naturally.