The nature of learning theories -- Thorndike's connectionism -- Guthrie's contiguous conditioning -- Skinner's operant conditioning -- Hull's systematic behavior theory -- Tolman's sign learning -- Classical Gestalt theory -- Lewin's field theory -- Freud's psychodynamics -- Functionalism -- The emergence of mathematical models -- Current Developments. I. Reinforcement and drive -- II. Some persisting issues - Retrospect and prospect.