Centola and Baronchelli have recruited subjects from the world wide web to play a live game. They demonstate that myopic players interacting in sequential pairs in social networks can unintentionally create percolating cascades of coordinated behavior. Their findings demonstrate that social conventions can spontaneously evolve in large human populations without any institutional mechanisms to facilitate the process. The results highlight the causal role played by network connectivity in the dynamics of establishing shared norms. I pass on first the abstract and then sections on experimental design and methods.
How do shared conventions emerge in complex decentralized social systems? This question engages fields as diverse as linguistics, sociology, and cognitive science. Previous empirical attempts to solve this puzzle all presuppose that formal or informal institutions, such as incentives for global agreement, coordinated leadership, or aggregated information about the population, are needed to facilitate a solution. Evolutionary theories of social conventions, by contrast, hypothesize that such institutions are not necessary in order for social conventions to form. However, empirical tests of this hypothesis have been hindered by the difficulties of evaluating the real-time creation of new collective behaviors in large decentralized populations. Here, we present experimental results—replicated at several scales—that demonstrate the spontaneous creation of universally adopted social conventions and show how simple changes in a population’s network structure can direct the dynamics of norm formation, driving human populations with no ambition for large scale coordination to rapidly evolve shared social conventions.Experimental Design
Each live game, or experimental “trial,” consisted of a set of participants, a specific social network structure, and a prespecified number of rounds to play. When participants arrived to play the game, they were randomly assigned to positions within a social network. In a given round of the game, two network “neighbors” were chosen at random to play with one another. Both players simultaneously assigned names to a pictured object (i.e., a human face), blindly attempting to coordinate in the real-time exchange of naming choices. If the players coordinated on a name, they were rewarded with a successful payment; if they failed, they were penalized (Materials and Methods). After a single round, the participants could see only the choices that they and their partner had made, and their cumulative pay was updated accordingly. They were then randomly assigned to play with a new neighbor in their social network, and a new round would begin. The object that participants were trying to name was the same for the entire duration of the game, and for all members of the game. Participants in the study did not have any information about the size of the population that was attempting to coordinate nor about the number of neighbors to whom they were connected.Materials and Methods
Participants in the study were recruited at large from the World Wide Web. When participants arrived to play a game, they were randomly assigned to an experimental condition (i.e., a social network) and then randomly assigned to a position within that social network. In a given round of the game, two network neighbors were chosen at random to play with one another. Both players simultaneously assigned names to a pictured object (e.g., a human face), blindly attempting to coordinate in the real-time exchange of naming choices. If the players coordinated on a name, they were rewarded with a successful payment ($0.50); if they failed, they were penalized (–$0.25). (Participants could not go into debt, so failures did not incur a penalty if a participant had a balance of $0.) After a single round, the participants could see only the choices that they and their partner had made, and their cumulative pay was updated accordingly. They were then randomly assigned to play with a new neighbor in their social network, and a new round would begin. The object that participants were trying to name was the same for the entire duration of the game and for all members of the game. An experimental trial concluded when all members completed the specified number of rounds. Participants did not have any information about the size of the population nor about the number of neighbors to whom they were connected nor even about which individuals they were interacting with in a given round. We explored the dynamics of convention formation over different network sizes between 24 and 96 and degrees of social connectedness. However, the controls within the experimental design ensured that the informational resources provided to subjects were identical across all conditions of the study.
