Synopsis Applied psychology is the functional side of the discipline of psychology. The knowledge gained in the field of psychology as to how people learn and how human behaviour can be modified is applied to practical side of life in the classroom, in the factory and in the army. The first decade of the twentieth century marked the culmination of a shift in the subject-matter of psychology from mind to behaviour. The shift was not sudden nor was it solely the product of the Behaviourist movement. The latter movement was rather the climax to changes which began during the last two decades of the nineteenth century. Behaviour. Manifestations of mind had become more and more the objects of study until they acquired an interest status of their own and finally mind or mental reactions came to be treated as instances of behaviour. One of the remarkable consequences of this shift of emphasis and of the broadening of the concept of behaviour has been that the behaviour of people the world over and not some highly abstract behaviour in the laboratory became the subject-matter of psychology.