Acyclic digraphs arise in many natural and artificial processes. Among the broader set, dynamic citation networks represent a substantively important form of acyclic digraphs. For example, the study of such networks includes the spread of ideas through academic citations, the spread of...

Objectives To evaluate whether happiness can spread from person to person and whether niches of happiness form within social networks. Design Longitudinal social network analysis. Setting Framingham Heart Study social network. Participants 4739 individuals followed from 1983 to 2003. Main...

We recently showed that obesity can spread socially from person to person in adults (Christakis and Fowler 2007). A natural question to ask is whether or not these results generalize to a population of adolescents. Three separate teams of researchers have analyzed the National Longitudinal Study...

Previous research has indicated that higher levels of social interactions, or greater social capital, tend to create higher levels of civic engagement and social trust. We used a large, nationally representative longitudinal survey of youth to examine the relationship between social capital, as...

Why do individuals engage in personally costly, partisan activities that benefit others? If individuals act according to rational self-interest, then partisan activity occurs only when the benefits of that activity exceed its costs. However, laboratory experiments suggest that many people are...

Altruism refers to a willingness to pay a personal cost to make others better off. Past research has established a link between altruism and political participation, primarily among college students. We show that dictator game behavior predicts support for humanitarian norms and donations to...

Models of political participation have begun to incorporate actors who possess "social preferences". However, these models have failed to take into account the potentially incongruent political goals of different social preference types. These goals are likely to play an important role in...

We conduct experiments in which subjects participate in both a game that measures preferences for income equality and a public goods game involving costly punishment. The results indicate that individuals who care about equality are those who are most willing to punish free-riders in public...

Prospect theory scholars have identified important human decision-making biases, but they have been conspicuously silent on the question of the origin of these biases. Here we create a model that shows preferences consistent with prospect theory may have an origin in evolutionary psychology....

Background: The prevalence of obesity has increased substantially over the past 30 years. We quantitatively explored the nature and extent of person-to-person spread of obesity as a possible contributing factor explaining this increase. Methods: We developed a densely interconnected social...