title: Testosterone administration decreases generosity in the ultimatum game.
abstract: 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.
authors.affiliation: Center for Neuroeconomics Studies, Claremont Graduate University, Claremont, California, USA. paul@pauljzak.com
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Zak
authors.forename: Robert
authors.initials: R
authors.lastname: Kurzban
authors.forename: Sheila
authors.initials: S
authors.lastname: Ahmadi
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Swerdloff
authors.forename: Jang
authors.initials: J
authors.lastname: Park
authors.forename: Levan
authors.initials: L
authors.lastname: Efremidze
authors.forename: Karen
authors.initials: K
authors.lastname: Redwine
authors.forename: Karla
authors.initials: K
authors.lastname: Morgan
authors.forename: William
authors.initials: W
authors.lastname: Matzner
mesh_terms: D000533:Altruism; D003657:Decision Making; D013196:Dihydrotestosterone / Q000097:blood; D005717:Games, Experimental; D006801:Humans; D008297:Male; D010919:Placebos; D013739:Testosterone / Q000008:administration & dosage* / Q000097:blood; D055815:Young Adult
chemical_list: D010919:Placebos; D013196:Dihydrotestosterone; D013739:Testosterone