Grossly oversimplifying, the following models of mind can be discerned in the welter of contemporary psychological theorizing. The first model of the mind is mind as an energy system. This is represented by early psychoanalytical theory, particularly by its dynamic and economic versions. It has also represented by ecologists (Tinbergen, 1951) and by drive reduction theorists. In this model, the stress is on the concept of motivation, conceived as drive. Common to the theories that regard mind as an energy system are the ideas of homeostasis and closed system. The metaphor of energy is often used by motivation theorists who view drives, instincts, and needs as types of forces.

p. 102 - Models of Mental Illness (1984)