R.W. Toseland and R.F. Rivas list the five theories important to group practice:

1. Psychoanalytic theory (Freud, et al.)
2. Learning theory (Bandura)
3. Field theory (Lewin)
4. Social exchange or interaction theory (Blau; Homans; Thibaut & Kelly)
5. Systems theory (Anderson; Olsen)

Cartwright and Zander add four others:

1. Sociometric orientation (Jennings; Moreno)
2. General psychology orientation (looking at individual group members)
3. Empiricist-statistical orientation or group syntality theory (Cattell)
4. Formal models orientation (French & Snyder; Horary, Norman & Cartwright; Simon)