A new study has found that testosterone supplements made people more sensitive to moral norms, suggesting that testosterone’s behavioral influence is a lot more complicated than previously thought.

The University of Texas at Austin research looked at the hormonal influence of moral decision making. Previous research has investigated moral judgment based on behavioral responses and brain activity. The current research goes further than this to analyze the role of deep-seated biological factors, in particular from testosterone.

“There’s been an increasing interest in how hormones influence moral judgments in a fundamental way by regulating brain activity,” according to Bertram Gawronski, a Psychology professor at Austin. “To the extent that moral reasoning is at least partly rooted in deep-seated biological factors, some moral conflicts might be difficult to resolve with arguments.”

The researchers used the “philosophy’s train trolley” problem to measure the influence of testosterone on moral decision making. The trolley problem is one of the most famous thought experiments in philosophy. In the problem, a train trolley will kill five people unless someone chooses to pull a lever, moving the trolley to another track, where it will kill one person only.

Researchers used dilemmas associated with real-life events, simulations that confront utilitarian decisions, which focus on the greater good, – saving a large group of people, against the morality of action decisions, which focus on moral norms, – avoiding action that would harm someone.

Previous research on the hormones influence of moral judgment suggested that higher testosterone levels are associated with stronger utilitarian preferences. The researchers tested the hypothesis in a double-blind study that administered testosterone to a group of 100 people and a placebo to another 100 people.

“The study was designed to test whether testosterone directly influences moral judgments and how,” according to Skylar Brannon, at UT Austin. “Our design also allowed us to examine three independent aspects of moral judgment, including sensitivity to consequences, sensitivity to moral norms and general preference for action or inaction.”

Unlike previous studies where heightened testosterone was linked to utilitarian judgments, the researchers found that those who received testosterone supplements were less likely to act for the greater good and instead became more sensitive to moral norms. However, participants with high levels of naturally occurring testosterone showed the opposite, making judgments that were less sensitive to moral norms.

The researchers hypothesize that naturally occurring testosterone could be associated with certain moral judgments, as people with particular traits tend to have varying levels of testosterone — high levels of psychopathy tend to have high levels of naturally occurring testosterone and exhibit lower sensitivity to moral norms. This doesn’t mean that testosterone is the cause of psychopaths’ insensitivity to moral norms, but as found in the current research, testosterone seems to have the opposite effect, increasing people’s sensitivity to moral norms.

“The current work challenges some dominant hypotheses about the effects of testosterone on moral judgments,” Gawronski said. “Our findings echo the importance of distinguishing between causation and correlation in research on neuroendocrine determinants of human behavior, showing that the effects of testosterone supplements on moral judgments can be opposite to association between naturally occurring testosterone and moral judgments.”


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