The Social Contagion of Generosity

Principal Investigator: Nicholas Christakis, Sociology, Harvard University

Co-Investigator: James Fowler, Political Science, University of California, San Diego

Generosity is a key predicate for the formation and operation of social networks, a fact only recently beginning to attract attention from network scientists, social scientists and biologists.

If people never really behaved generously or altruistically toward one another social ties would dissolve and the network around us would disintegrate. Some degree of generosity is therefore crucial for the emergence and endurance of social networks. Moreover, once networks are established, cascades of generous acts–from ordinary acts of kindness to organ donation–can spread through them. This project is grounded in the idea that understanding generosity requires taking account of the social connections in which the disposition to generosity occurs.

Christakis and his research team will use two different methodological approaches to study this phenomenon. First, they will continue a joint survey project done with Gallup that uses a representative sample of 3,000 Americans, to which they will add longitudinal follow-up. They will use the survey to collect information about respondents’ social networks and about their generosity, and will assess the relationship between these phenomena, paying particular attention to causal relationships.

Second, the research team will conduct behavioral experiments in which volunteers will be assembled into networks. These networks will then be led through sequences of interactions in a way that will allow researchers to test whether we can induce cascades of generosity such that generosity spreads from person to person to person within the network.

With these two types of data, Christakis and his research team pose two broad sets of questions and hypotheses. First, using the survey data they will evaluate whether or not structural aspects of people’s social relationships (such as how many friends they have or whether their friends know each other) affect how how generous they are. Perhaps people with more friends are more generous; or perhaps they have more friends precisely because they are more generous. Or perhaps people whose friends are close to one another are more generous , compared to those whose friends don’t get along with one another.

Second, using the experimental data, researchers will evaluate whether or not generosity can spread from person to person to person. They hypothesize that acts of kindness and altruism can spread, and that if I am generous to you, you will be generous to others (and not just to me). Determining the extent of this phenomenon, and the rules governing it, has important implications for our understanding of generosity, its determinants and its consequences.