We test the hypothesis that "genuine" or "convincing" smiling is a costly signal that has evolved to induce cooperation in situations requiring mutual trust. Potential trustees in a trust game made video clips for viewing by potential trusters before the latter decided whether to send them...

Two recent failures of the United States intelligence system have led to the creation of high-level investigative commissions. The failure to prevent the terrorist attacks of 9/11 prompted the creation of the 9/11 Commission, and the mistaken belief that Saddam Hussein had retained weapons of...

In this chapter, we provide an overview on the literature on key players in networks. We first introduce the theoretical concept of the key player, which is the agent that should be targeted by the planner so that, once removed, she will generate the highest level of reduction in total activity....

We develop a dynamic network formation model that can explain the observed nestedness in real-world networks. Links are formed on the basis of agents’ centrality and have an exponentially distributed life time. We use stochastic stability to identify the networks to which the network formation...

We provide an overview on networks in economics. We first look at the theoretical aspects of network economics using a game-theoretical approach. We derive some results on games on networks and network formation. We also study what happens when agents choose both links and actions. We then...

We provide an overview and synthesis of the literatures analyzing games where players are connected via a network structure. We study, in particular, the impact of the structure of the network on individuals’ behaviors. We focus on the game theoretic modeling, but also include some discussion...

We develop an unified model embedding different behavioral mechanisms of social interactions and design a statistical model selection test to discriminate between them in empirical applications. This framework is applied to study peer effects in education and delinquent behavior for adolescents...

We consider a model where the criminal decision of each individual is affected by not only her own characteristics, but also by the characteristics of her friends (contextual effects). We determine who the key player is, i.e. the criminal who once removed generates the highest reduction in total...

We analyze delinquent networks of adolescents in the United States. We develop a dynamic network formation model showing who the key player is, i.e. the criminal who once removed generates the highest possible reduction in aggregate crime level. We then structurally estimate our model using data...

We survey the literature on social networks by putting together the economics, sociological and physics/applied mathematics approaches, showing their similarities and differences. We expose, in particular, the two main ways of modeling network formation. While the physics/applied mathematics...