The role of testosterone in value-based decision making - An exploratory investigation into the effects of testosterone on choice behavior and its underlying psychological processes

Both human and non-human animal studies have shown that the steroid hormone
testosterone plays an important role
in motivated behaviors and decision making. Testosterone administration in
humans has been reported to have effects
on different types of value-based decisions (such as risky, intertemporal, and
social decisions), but findings have been
inconsistent. Further, knowledge on how testosterone affects the psychological
mechanisms underlying such decisions
is scarce. The main objective of our research is therefore to develop insights
into how testosterone modulates the
psychological mechanisms by which it affects different types of value-based
decisions and choice behavior.

Primary objective:
- To identify the psychological mechanisms via which testosterone modulates
value-based decision making, such as
testosterone's effects on risk-taking levels, impulsivity and self-control in
intertemporal choice, and social learning in
reward-based decision making.

Secondary objectives:
- To examine choices made in contexts such as risky and intertemporal choice,
and reward-based choice involving
individual and social learning
- To causally investigate whether and how testosterone effects moderators of
decision making, such as impulsivity
versus self-control, use of reward history, and social information in
value-based decisions, personality variables and/or
cortisol levels

Participants will be tested in a randomized, double-blind, placebo controlled,
between-group design. The experiment
consists of one test session at the Behavioral Science Institute. Participants
will receive either 0.5 mg testosterone or a
placebo dose by sublingual administration and will perform several computerized
tasks. In addition, they will complete
several self-report questionnaires. The total duration of the experiment will
be 5.5 hours (including a waiting period of
3.5 hours between testosterone administration and task administration).

One group of participants will receive a single dose of 0.5 mg testosterone;
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
and there are no known side-effects. The sublingual testosterone administration
procedure that we will use has been
used extensively for about a decade in psychological studies at Utrecht
University (Hermans et al., 2006a, 2006b,
2007, 2008; Schutter & van Honk, 2004; van Honk et al., 2001, 2004, 2005; van
Honk & Schutter, 2007), and none of
the studies reported negative side effects. In addition, the PI on this project
(Prof dr Karin Roelofs) has been using the
same sublingual testosterone administration procedure in several studies,
namely an fMRI study in healthy female
participants at Radboud University (CMO Protocol ID: NL34927.091.10) and two
studies at Leiden University, one in
healthy female participants and one in female patients with social anxiety
disorder (CMO Protocol ID: P09.164). Thus
far, none of the participants in these studies have reported negative side
effects, and no adverse events have occurred
in these studies.
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.