Paul J. Zak; Angela A. Stanton; Sheila Ahmadi

“ Although we artificially raised OT levels in this study to establish a causal mechanism producing generosity, OT can be enhanced nonpharmacologically in a variety of ways, including touching, safe environments, and receiving a signal of trust from another person [23] , [25] . By increasing OT the ability to empathize with others, and the motivation to be generous with them, are enhanced. Indeed, mice that lack OT receptors suffer from social amnesia [48] . This suggests that a variety of factors we encounter in our daily lives may motivate us to be generous—even with strangers. ”

“ Two tasks were used to dissociate the physiologic role of empathy in producing generosity and altruism using monetary transfers. Monetary transfers were used to obtain objective and active measures of generosity and altruism.
A simple mathematical model will clarify our experimental approach (related models have been proposed [27] – [28] , and others) . Consider a dyadic interaction between two individuals, i and j. Let bi be the benefit that i receives, and bj the benefit to j. Individuals obtain utility from receiving their own benefit, and possibly from the other person receiving a benefit. ”

“ We have shown that OT raised generosity in the UG by 80% over placebo, and that generous participants left the experiment with less money. The increased generosity was not due to greater altruism because OT did not affect transfers in the DG, and the impact of OT on generosity remains significant even when altruism in the DG was taken into account. This finding is consistent with a recent fMRI study of charitable giving that found evidence for both altruism and “warm glow” motivations for charity [22] . ”

“ Our experimental design increased OT in one-half of the participants with the expectation that DM1s would have a more acute understanding of how DM2s would react to an offer in the UG. Because OT receptors in the human brain are preferentially located in areas associated with emotions and social behaviors (especially the amygdala, hypothalamus, and anterior cingulate [35] – [36] ) , this suggests a role for emotions in supporting generosity. Emotional engagement is less important in the DG as one simply decides how much one would like to give up. ”

“ Reciprocal altruism is giving with an expectation of equal or larger future return from the same person. Yet much charitable giving and direct helping of others does not appear to provide direct reciprocation, for example, volunteering or donating blood [2] . ”

“ OT and altruism together predicted almost half the interpersonal variation in generosity. Notably, OT had twofold larger impact on generosity compared to altruism. This indicates that generosity is associated with both altruism as well as an emotional identification with another person.
Introduction
Human beings show considerable generosity toward strangers. In 2005, over $260 billion was given to U.S. charities, with $199 billion (77%) of this given by individuals [1] . The absolute amount of charitable giving is not only high, but the proportion of income donated has grown. ”

“ All participants were asked to make choices as DM1 and DM2 in the UG, and as DM1 in the DG. Payoffs were determined by randomly assigning participants to be either DM1 or DM2 in the UG, and as DM1s in the DG. After the experiment, participants were paid their earnings in private by a lab administrator.Competing Interests: The authors have declared that no competing interests exist.Funding: PJZ thanks the Seaver Institute and the John Templeton Foundation for financial support. Neither the Seaver Institute nor the John Templeton Foundation had a role in the conduct of this study. ”

“ Hassan, O; et al. (2003) , ““As you would have them do unto you”: Does imagining yourself in the other's place stimulate moral action?”, Pers Soc Psychol B 29: 1190–1201 ↑ Camerer, C (2003) , Behavioral game theory experiments in strategic interaction., New York: Russell Sage Foundation, p. 544 1 2 3 4 Kosfeld, M; Heinrichs, M; Zak, PJ; Fischbacher, U & Fehr, E (2005) , “Oxytocin increases trust in humans.”, Nature 435: 673–676, 15931222, pmid:15931222 ↑ Xiao, E & Houser, D (2005) , “Emotion expression in human punishment behavior.”, PNAS 102: 7398–7401, 15878990, pmid:15878990 ↑ Sanfey, AG ”