A psychologist as well as physician, Seguin was a pupil of the Parisian doctor Jean Itard, who became famous for his work on mental retardation and his attempts to educate a boy who had apparently lived nearly all of his eleven or twelve years in the woods of central France. Although Itard considered these attempts a failure because the boy learned only a few words, Seguin was impressed with the fact that he was able to master a number of useful habits. This led him to the realization that even though mentally defective children could not be brought up to normal, they still possessed capacities which could be trained and developed.Itard’s educational methods were based on principles of the associationist school, which holds that an accumulation of sensory experience is the basis of all mental growth. Seguin built on this approach by applying what he called the “physiological method” of developing the motor and sensory capacities of the mentally deficient. His procedures included various activities designed to promote motor co-ordination, such as climbing ladders or walking along lines, and a wide range of experiences aimed at educating the senses, including exposure to bright colors, varied sounds, and objects of different shapes. These techniques influenced the Italian educator Maria Montessori, who developed materials and procedures which are now being applied not only to defective but to normal children.Seguin’s work had a profound effect on the treatment of the mentally retarded. The accepted approach at his time was merely custodial, but as a result of his discoveries, constructive educational programs were introduced, and the defective were treated with greater understanding and humanity. Patients who had ordinarily been classified as hopeless showed great improvement, and the attitude of the public as well as the institutions began to change for the better.In 1842 Seguin became the director of an institution for the feeble-minded in Paris, but in 1848 he had to leave the country because of his Christian Socialist political views. He accepted an invitation to the United States, sent by professional people who wanted to see his methods adopted in this country.He remained here for the rest of his life, establishing constructive educational programs in a large number of institutions.Seguin’s most important works were Traitement Morale; Hygiene et Education des Idiots (1848) and Idiocy, Its Treatment by the Physiological Method (1866). Though these books are rarely read today, one of his tests is still in use: the Seguin formboard test, which presents blocks of various shapes to be fitted into cutouts on a wooden board.In assessing Seguin’s contributions, Murphy (1949) calls him “the greatest figure in the century in the training of mental defectives.”