In-group favouritism and out-group discimination in naturally occurring groups

We study in-group favouritism and out-group discrimination in a multiplayer dictator game.  An allocator divides a large sum of money among three groups of 20 recipients each and Self.  Allocations to groups are divided equally among the group members.  The three groups are supporters of the two rival political movements in Thailand (“yellow shirts†versus “red shirtsâ€) and political neutral subjects.  A control treatment with artificial groups (“group Aâ€, “group Bâ€, and “non-affiliatedâ€) is also conducted.  We find that allocators strongly favour their own group and discriminate against supporters of the rival party.  Despite a strong anti-corruption stance of the yellow-shirt movement members of both political groups are indistinguishable in both favouritism and discrimination.  Allocators tend to be rather selfish: on average 45% of the pie is given to Self, despite the large number of recipients.