To be entered in the Group Dynamics article, under the Group Influence on individual behavior section.

Past research has also indicated further work on ingroups and outgroups. For instance, research has identified preferential treatment for ingroup members (Brewer 1999). There has been some work suggesting that different activities such as video games can show reduced negativity between different group members (Velez et al. 2014). Furthermore, cooperation has been identified as highest between ingroup members (Dion 1973). This approach can also be extended towards politics. For instance, ingroup politicians have been seen to trust each other more than outgroup members (Munro et al. 2010). Much work has pointed to self-esteem as a reason for ingroup favoritism (Turner et al. 1979).