Testosterone administration modulates moral judgments depending on second-to-fourth digit ratio.

Area of Science:

• Neuroscience
• Psychology
• Endocrinology

Background:

• Moral judgment integrates emotions and social cognition.
• Testosterone may influence moral reasoning, as males exhibit more utilitarian decisions.
• Previous studies link salivary testosterone to utilitarian choices, but direct evidence is lacking.

Purpose of the Study:

• To investigate the role of testosterone in moral reasoning.
• To examine how prenatal sex hormone priming, proxied by digit ratio (2D:4D), modulates the effects of testosterone administration on moral judgment in females.

Main Methods:

• A placebo-controlled, within-subjects design was employed with 20 young females.
• Participants received testosterone or placebo.
• The second-to-fourth digit ratio (2D:4D) was measured as a proxy for prenatal hormone exposure.

Main Results:

• Digit ratio (2D:4D) predicted 44% of the variance in testosterone's effect on moral judgment.
• Higher 2D:4D (indicating higher prenatal estradiol) correlated with increased utilitarian judgments after testosterone administration.
• Lower 2D:4D (indicating higher prenatal testosterone) correlated with more deontological judgments after testosterone administration.

Conclusions:

• Prenatal sex hormone priming significantly influences how individuals respond to testosterone later in life regarding moral decisions.
• Differences in brain aromatase activity, affecting testosterone-to-estradiol conversion, may underlie these effects.
• Early neurodevelopmental effects of sex steroids are crucial for understanding the activational effects of hormones on adult moral reasoning.