The role of testosterone in value-based decision making

Rationale:

Testosterone plays a major role in motivated behavior. However, it remains unknown how testosterone affects the psychological mechanisms underlying value-based decision making and choice behavior. In the current study we will investigate the psychological mechanisms by which testosterone influences important types of decisions, such as risky and intertemporal choices, and learning based on reward history versus social input. We conduct a placebo-controlled double-blind testosterone administration study to causally investigate testosterone's role in these types of decisions.



Study objective:

To identify the psychological mechanisms via which testosterone modulates value-based decision making (we use the term value-based decisions as it covers all the types of decisions we investigate in the study, i.e., decisions in both social and non-social contexts).



Study design:

Participants will be tested in a randomized, double-blind, placebo controlled, between-group design.



Study population:

Participants will be healthy female volunteers between 18 and 35 years of age.



Intervention:

One group of participants will receive a single dose of 0.5 mg testosterone. Another group will receive a similar dose of a matched placebo.



Main study parameters/endpoints:

1. Behavioral performance on computerized tasks assessing choice behavior and their underlying psychological mechanisms

2. Testosterone and cortisol hormone levels measured in saliva

3. Subjective measurements on self-report questionnaires

Two often-iterated and relatively widespread, but probably too narrow, views of testosterone are that (a) it is first and foremost a "social" hormone, and that (b) higher levels of testosterone are associated with mainly negative consequences. However, more recent evidence suggests that testosterone effects actually extend beyond the purely social domain and are not only negative but depend on the context. However, under which circumstances which effect is to be expected is not known. Furthermore, very little is known about the underlying (psychological) mechanisms by which testosterone affects decisions and behaviors. Therefore, the current study investigates how testosterone influences value-based decision making in a social versus non-social context, using different paradigms that allow decomposition into underlying mechanisms. Based on the literature, we derived two competing hypotheses:

1) Testosterone has effects in a social context only, and will have negative consequences on decision-making (i.e., resulting in less pro-social choices);

(2) Testosterone will have effects in both a social and non-social context, and will result in more optimal, goal-directed choices (i.e., maximizing own benefit).

The intervention was completed in a single session of 6 hours and 30 minutes.

Participants will receive either 0.5 mg testosterone or a placebo dose by sublingual administration and will perform several computerized tasks and complete several self-report questionnaires. The total duration of the experiment will be 6 hours and 30 minutes, including a 3.5 hours waiting period between drug administration and behavioral testing and 2 hours of experimental tasks. Furthermore, participants will provide 5 saliva samples in total to measure testosterone and cortisol levels.