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.
