The Emergence of “Us and Them” in 80 Lines of Code: Modeling Group Genesis in Homogeneous Populations Newer:Social Heuristics Shape Intuitive CooperationOlder:What Does “Clean” Really Mean? The Implicit Framing of Decontextualized Experiments PostedFebruary 22, 2014 AuthorScienceSites Categories2014, journal-article Tags2014, Cooperation, Intergroup, Social networks, Computer models