Testosterone Administration Decreases Generosity in the Ultimatum Game

• Published in: PloS one Vol. 4; no. 12; p. e8330
• Main Authors: Zak, Paul J., Kurzban, Robert, Ahmadi, Sheila, Swerdloff, Ronald S., Park, Jang, Efremidze, Levan, Redwine, Karen, Morgan, Karla, Matzner, William
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 16.12.2009; Public Library of Science (PLoS)
• Subjects: Altruism; Androgens; Behavior; Blindness; Decision Making; Dihydrotestosterone - blood; Drug dosages; Empathy; Endocrinology; Experiments; FDA approval; Games, Experimental; Humans; Male; Males; Medical research; Medical screening; Men; Neuroscience/Behavioral Neuroscience; Neuroscience/Experimental Psychology; Neuroscience/Psychology; Placebos; Studies; Testosterone; Testosterone - administration & dosage; Testosterone - blood; Young Adult; United States > US; California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0008330

How do human beings decide when to be selfish or selfless? In this study, we gave testosterone to 25 men to establish its impact on prosocial behaviors in a double-blind within-subjects design. We also confirmed participants' testosterone levels before and after treatment through blood draws. Using the Ultimatum Game from behavioral economics, we find that men with artificially raised T, compared to themselves on placebo, were 27% less generous towards strangers with money they controlled (95% CI placebo: (1.70, 2.72); 95% CI T: (.98, 2.30)). This effect scales with a man's level of total-, free-, and dihydro-testosterone (DHT). Men in the lowest decile of DHT were 560% more generous than men in the highest decile of DHT. We also found that men with elevated testosterone were more likely to use their own money punish those who were ungenerous toward them. Our results continue to hold after controlling for altruism. We conclude that elevated testosterone causes men to behave antisocially.