Work psychology applies psychology in the workplace. It sounds simple and clear-cut: there is a scientific body of knowledge about the individual called psychology and in this branch it is applied to the study of individuals at work. At the physiological end, ergonomics overlaps with industrial psychology, through the psycho-physiological, experimental tradition. In the United States, industrial psychology and human relations or organizational behaviour have existed relatively independently of each other, the latter being fraternized by a majority of non-psychologists and identified with management ideas. Work psychology has thrived by mingling with management training, human resource development, and personnel management. Three areas of scientific management became the province of industrial psychology: training workers in new methods devised by management; design of tools; and selection. Selection was based on the use of psychological tests for the measurement of various job-related skills such as visual acuity and finger dexterity.