"If you define a situation as real, it is real to you in its consequences...however, your definition of a situation may be influenced by how others define the same situation." This simple paradigm calls into question the four disciplines of Sociology, Cultural Anthropology, Social Psychology and Traditional psychology and how they relate to each other and to their various definitions of society. Perhaps they should be grouped into a single discipline called Cultural Sociology. (Which would include all four disciplines and certain studies within Economics, History, Political Science, Statistics and Chaos Theory.)
The book, "Neighbors: The Destruction of the Jewish Community in Jedwabne, Poland" [1] describes the situational dynamics of [mass murder]?. See Holocaust.
Groups behave similarly. That is the beauty of situational dynamics. Take the Nazi movement of Germany. Simplistically, The German people defined their previous few decades as misery from which they were de-throned from their perch of intellectual superiority. Hitler exploited their self interest to become a super-race again. Their social inhibitions were diminshed through the use of propoganda which weakened their Anchors of attitude on human life as applied to the Jewish people. The social interaction with others helped create a majority willing to sacrifice millions for Hitler's cause.
The same thing happens when you stump your toe. Example. You stump your toe (Circumstance) after your wife is critical of some act you may have done (Social interaction) . Your blood pressure rises (Weakening your inhibitions). You decided (Self interest) that you aren't mad because of your inability to walk correctly (afterall, anyone can walk), so you re-define the situation as your wife's fault for being critical and get angry with her.
While this applies readily to aggression, it also applies to almost any human emotional response as well. It was Leon Festinger who first brought up the idea of Cognitive Dissonance. (Being uncomfortable) and how humans will do almost anything to bring balance and comfort...usually in a way that makes them or the group be seen in the most favorable light.