The role of testosterone in social decision-making - An exploratory investigation into the effects of testosterone on human brain and behavior

Animal studies showed that the steroid hormone testosterone plays an important
role in social behavior. Recent evidence suggests that testosterone is involved
in human social behavior as well. Testosterone administration in humans has
been reported to enhance social dominance and reduce anxiety, but findings have
been inconsistent. Further, knowledge on how testosterone affects the brain
mechanisms underlying social behavior is scarce. The main objective of our
research is therefore to develop insights into how testosterone modulates the
neural correlates of interactive social decision-making.

Primary objective: To identify the neural mechanisms via which testosterone
modulates social decision-making. Secondary objectives: - To provide an
extension of observed behavioral effects of testosterone on decision-making,
specifically to examine decisions made in a social context - To identify
whether testosterone is involved in social risk-taking or in risk-taking in
general - To evaluate whether the effect of testosterone on social
decision-making is moderated by personality variables - To contribute to a
better understanding of the neuroendocrine systems underlying social mental
disorders

Participants will be tested in a randomized, double-blind, placebo controlled,
between-group design. Participants will receive either testosterone or a
similar placebo dose and perform computerized tasks in an MRI scanner. Brain
images will be used to identify the effects of testosterone on the neural
correlates of social decision-making. After scanning, participants will
complete several self-report questionnaires.

One group of participants will receive .5 mg of testosterone through sublingual
administration, and the other group will receive a similar dose of placebo.

The low dose of testosterone can be administered safely to humans without any
relevant risk of serious adverse events. On both the day prior to the test
session and on the day of the test session itself participants will adhere to
some simple restrictions with respect to medication, alcohol and drug intake.
During the morning of the test session participants will refrain from smoking
and consuming stimulant-containing drinks. The risk associated with
participation can be considered negligible and the burden can be considered
minimal. No adverse events are expected and side effects of the treatment are
very unlikely.