If behavior is the essential object of psychological interest, then psychology is the science of behavior. This indeed is one of the most widely accepted definitions. It has but one drawback: the limitations set upon the term behavior. In common usage this term refers only to outward adjustment, whereas psychologists are interested quite as much in the internal and abbreviated adjustments, in the processes of thought, emotion, feeling, and perception. This being the case we would suggest the term activity in place of the term behavior, and define psychology as the science of the activity of the individual, including under activity the implicit as well as the explicit, the incomplete and fragmentary adjustments usually called mental as well as the more overt and manifest usually called physical