Sutherland observed the reactions of medical residents to instruction in a new field of learning and concluded that their attitudes toward the material and the teacher could be understood in terms of Freud's theory of psychosexual development. He was able to show how oral, anal, phallic and genital attitudes were present in the student at different times. On this basis he suggests that the teacher's reactions to the student's learning may decisively complicate the learning process. Furthermore, he hypothesizes that psychosexual development itself can be looked upon as a learning process and generalizes to the effect that all new stimuli to which the organism is exposed may be handled successively by the different modes of operation characteristic of the stages of infantile psychological development.