Group dynamics form a basis for much group therapy. Politicians and salesmen may make practical exploitations of principles of group dynamics for their own ends.
Compare crowd psychology.
A group goes through four main phases: forming (pretending to get on), storming (knowing they don't get on and being angry), norming (getting used to each other) and performing (working in a group to a common goal). It should be noted that this refers to the majority of the group, but of course individuals in a group work different ways.
Wilfred Bion studied group dynamics from a psychoanalytic perspective. Many of his finding were reported in his published books, especially Experiences in Groups, London, Tavistock, 1961. Tavistock Institute has further developed and applied the theory and practices developed by Bion.
Further reading
Also see