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.

Testosterone administration does not affect men's rejections of low ultimatum game offers or aggressive mood

“…Two other studies have administered T to participants in the ultimatum game with mixed evidence. The first study was a withinsubjects experiment conducted with men which found that T decreased generosity (Zak et al, 2009). However, their results are only significant when considering repeated observations from each subject (N = 25) as statistically independent.…”

“…There are several important challenges to our understanding of the effects of T on dominance and aggression in humans. Firstly, there are very few studies involving direct manipulation of T in men (Kouri et al, 1995;Pope et al, 2000;O'Connor et al, 2004;Zak et al, 2009;Welling et al, 2016;Carré et al, 2016). Evidence from studies in humans is largely correlational, and, therefore, severely limited when it comes to assessing causal relationships.…”

“…Some exceptions of recent work involving T administration in healthy men include Zak et al (2009), who report suggestive evidence that it decreased generosity, 1 Wibral et al (2012) who found that it reduced lying, Carré et al (2015) who showed that it impaired socio-cognitive ability only in subjects with low 2D4D or low psychopathic traits, Cueva et al (2015) who found that it increased risk-taking in an investment task, and Carré et al (2016) who found that it led to greater aggression only in subjects scoring high in trait dominance or low in trait self-control.…”

Do risk and time preferences have biological roots?

“…The caveat is that the invasive nature of these experiments precludes their wider adoption. For example, oxytocin administration to females may cause miscarriage (Zak et al, 2007) and testosterone administration has only been approved in males by the US Food and Drug Administration (Zak et al, 2009). …”

Salivary testosterone and cortisol are jointly related to pro-environmental behavior in men

“…Moreover, testosterone administration has been shown to reduce empathy (Hermans, Putman, & van Honk, 2006), collaborative decision-making (Wright et al, 2012), and generosity towards strangers (Zak et al, 2009). Notably, however, exogenous testosterone has also been reported to promote generosity (Eisenegger, Naef, Snozzi, Heinrichs, & Fehr, 2010) and reciprocity (Boksem et al, 2013) and to reduce lying (Wibral, Dohmen, Klingmüller, Weber, & Falk, 2012) in situations where the display of prosocial behavior is instrumental in gaining social status.…”