El origen social del altruismo: una literatura emergente

Revista Desarrollo y Sociedad, 2006

This paper analyzes the emerging literature on the determinants of giving within a social network. We propose two main explanatory variables for previous experimental results on the friendship effect. The first is social integration, which has a positive impact on giving. The second variable is strategic and is based on reciprocity: the * María Paz Espinosa acknowledges financial aid from UPV and MCT (BEC2003-02084); Pablo Brañas-Garza from DGCYT (SEJ2004-07554/ECON) and GV (GV06/275). We are indebted to two anonymous referees for their comments and suggestions. possibility of ex-post favors. Econometric analysis shows that both variables play a positive (and significant) role.

2006

This paper analyzes the emerging literature on the determinants of giving within a social network. We propose two main explanatory variables for previous experimental results on the friendship effect. The first is social integration, which has a positive impact on giving. The second variable is strategic and is based on reciprocity: the possibility of ex-post favors. Econometric analysis shows that both variables play a positive (and significant) role.

2006

T his paper explores the role of social integration on altruistic behavior. To this aim, we develop a twostage experimental protocol based on the classic Dictator Game. In the first stage, we ask a group of 77 undergraduate students in Economics to elicit their social network; in the second stage, each of them has to unilaterally decide over the division of a fixed amount of money to be shared with another anonymous member in the group. Our experimental design allows to control for other variables known to be relevant for altruistic behavior: framing and friendship/acquaintance relations. Consistently with previous research, we find that subjects favor their friends and that framing enhances altruistic behavior. Once we control for these effects, social integration (measured by betweenness, a standard centrality measure in network theory) has a positive effect on giving: the * We thank CICYT for financial assistance (BEC2003-02084; SEJ2004-07554/ECON).

SSRN Electronic Journal, 2007

We conduct field experiments in a large real-world social network to examine why decision-makers treat their friends more generously than strangers. Subjects are asked to divide a surplus between themselves and named partners at varying social distances, but only one of these decisions is implemented. We decompose altruistic preferences into baseline altruism towards strangers, and directed altruism towards friends. In order to separate the motives that are altruistic from the ones that anticipate a future interaction or repayment, we implement an anonymous treatment in which neither player is told at the end of the experiment which decision was selected for payment, and a non-anonymous treatment where both players are told the outcome. Moreover, in order to distinguish between different future interaction channels-including signaling one's propensity to be generous and enforced reciprocity, where the decision-maker grants the partner a favor because she expects it to be repaid in the future-the experiments include games where transfers both increase and decrease social surplus. We find that decision-makers vary widely in their baseline altruism, but pass at least 50 percent more surplus to friends as opposed to strangers when decision-making is anonymous. Under non-anonymity, transfers to friends increase by an extra 24 percent relative to strangers, but only in games where transfers increase social surplus. This effect increases with the density of the social network structure between both players. Our findings are well explained by enforced reciprocity, but not by signaling or preference-based reciprocity. We also find that partners' expectations are well attuned to directed altruism, but that they completely ignore the decision-makers' baseline altruism. Partners with higher baseline altruism have friends with higher baseline altruism and, therefore, are treated better by their friends.

Games and Economic Behavior, 2010

We report on a two-stage experiment in which (i) we first elicit the social network within a section of undergraduate students and (ii) we then measure their altruistic attitudes by means of a standard Dictator game. We observe that more socially integrated subjects are also more altruistic, as betweenness centrality and reciprocal degree are positively correlated with the level of giving, even after controlling for framing and social distance, which have been shown to significantly affect giving in previous studies. Our findings suggest that social distance and social integration are complementary determinants of altruistic behavior.

Groupe d'Analyse et de Théorie Economique Lyon …, 2008

We explore, first, if network structure and network embeddedness can account for the variation observed in individual generosity, and what characteristics of the network are important (if any). Second, if the influence of network structure and position is invariant across networks of different social and economic contents, and what different network characteristics are important for networks of different contents. Third, if there is explanatory room left for observable individual characteristics.

Biology Letters, 2011

Why are individuals altruistic to their friends? Theory suggests that individual, relationship and network factors will all influence the levels of altruism; but to date, the effects of social network structure have received relatively little attention. The present study uses a novel correlational design to test the prediction that an individual will be more altruistic to friends who are well-connected to the individual's other friends. The result shows that, as predicted, even when controlling for a range of individual and relationship factors, the network factor (number of connections) makes a significant contribution to altruism, thus showing that individuals are more likely to be altruistic to better-connected members of their social networks. The implications of incorporating network structure into studies of altruism are discussed.

Quarterly Journal of Economics, 2009

We conduct online field experiments in large real-world social networks in order to decompose prosocial giving into three components: (1) baseline altruism toward randomly selected strangers, (2) directed altruism that favors friends over random strangers, and (3) giving motivated by the prospect of future interaction. Directed altruism increases giving to friends by 52 percent relative to random strangers, while future interaction effects increase giving by an additional 24 percent when giving is socially efficient. This finding suggests that future interaction affects giving through a repeated game mechanism where agents can be rewarded for granting efficiencyenhancing favors. We also find that subjects with higher baseline altruism have friends with higher baseline altruism.

2006

We study why socially close neighbors make better agents than strangers. Using a series of modified dictator games and a new helping game we find that agents pass about 50 percent more surplus to friends compared to strangers when decision making is anonymous. This directed ...