James R. Angell (1869-1949) did much of his early work at the University of Chicago, which later became known as the origin of the functionalist tradition. He served as President of Yale University and was elected to the presidency of the American Psychological Association in 1906.
In 1904, Angell wrote an influential textbook, Psychology, in which he emphasized that the function of consciousness is to assist the organism in its successful adjustment to the environment. Functional psychology, as Angell defined it, should (1) study mental operations, rather than mental structure, (2) view consciousness in a utilitarian manner (i.e., as a useful tool for directing the organism), and (3) view mind and body as being functionally integrated, with no clear distinction between them. They function together to create successful adaptation to the environment. The proper study of psychology, then, is to determine how consciousness (or the mind) assists the organism in that adaptation.
By Angell’s time, functionalism had already been established. Indeed, Angell maintained that psychology had always been functional in character, and that it was the Structuralists who deviated from that. With Angell’s book (1904), functionalism became a serious alternative to Titchener’s structuralism. Functionalism focused American psychology on the importance of the external environment for behavior, paving the way for behaviorism and applied psychology (clinical, industrial, educational, counseling, military, etc.).