When it comes to moral decisions, testosterone doesn’t seem to do much

The hypotheses were based on previous suggestions that testosterone would make people less empathetic and therefore more likely to choose a purely utilitarian solution, minimizing the total number of deaths. They also hypothesized that people given testosterone would prefer taking action, which would bias them toward changing the status quo. To test these hypotheses, they got 200 volunteers and randomly assigned some to receive a boost of testosterone, while the rest got a placebo. The participants were then asked to consider a moral dilemma and come to some decision on what they felt the right course of action was.

Rather than simply looking at what the subjects chose, the researchers recognized that there were several potential tiers of decision-making at play. These included a general preference for action vs. inaction and possible preferences for moral prohibitions or utilitarian views. The participants’ responses were plugged in to a model that determined where they fell on these various values. The outcome of that analysis was used to test the various hypotheses.

“The results of the current study yielded no evidence in support of any of the four preregistered hypotheses,” write the authors. Those given testosterone were no more likely to prefer taking action than those given the placebo. It was predicted that they’d also be more prone to make utilitarian judgements that minimize total casualties; this wasn’t true, either. Another hypothesis suggested that those given testosterone would be less sensitive to moral prohibitions, such as not choosing to kill someone. In fact, the results suggest the exact opposite is true.