Cooperative Behavior Cascades in Human Social Networks

This article examines how an individual’s decision to cooperate or not cooperate in a game setting can influence subsequent interactions between other players. Previous research has shown that cooperative behavior can evolve in a fixed population as a result of repeated interactions. However, little is known about whether cooperative or uncooperative behavior can have a cascading influence on the behavior of people who were not part of the original decision.

The authors conducted a controlled experiment in which individuals were assigned to a sequence of groups to play one-shot public goods games. One set of games was an ordinary public goods game while the other set was a public goods game with the possibility of punishment. The authors studied the results of the sequence of games to see if the decisions made by individuals in a set affected the behavior of players in subsequent games who did not play in the original set.

Key Findings:

  • Players who observed cooperative or uncooperative behavior in their initial group were likely to reflect this behavior in future matches with different players. This influence persisted through three degrees of separation.
  • The result of this behavioral cascade is that the impact of initial cooperation is tripled through its indirect impact on subsequent opportunities to cooperate.
  • This cascading behavior occurred both in the ordinary public goods games and in the public goods with punishment game.

These findings suggest that cooperative behavior can cascade through social networks, meaning that a contribution made to the public good by an individual will be magnified by other individuals, even ones only indirectly influenced by the original contribution.

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