How Do Newcomers Blend into a Group?: Study on a Social Network Game

Cooperative behaviors are common in humans, and they are the fundamental basis of our society. We focused on multilevel selection, one of the theoretical frameworks used to study the evolution of cooperation. The evolution of cooperation by multilevel selection requires that the continual assortment between cooperators and noncooperators is generated, thus, humans may have acquired mechanisms that ensure assortment, e.g., migration between groups. However, human migration involves taking risks, because migrators cannot know whether they should join new groups. In a similar way, it is also too risky to interact with newcomers for existing members. This study aims to investigate this migration behavior that may generate the assortment between cooperators and noncooperators in a less restrictive environment. Especially, we explore how humans resolve the migration risks. Therefore, we research social interaction between newcomers (migrators) and existing group members in a social network game (SNG), wherein players can behave more freely compared to the environments used in previous studies. Our result suggests that migration which generated assortment between cooperators and noncooperators may have not been probably risky in human society. Moreover, we found interesting differences between newcomers and existing group members in social interaction.