Stanley Smith Stevens (November 4, 1906 – January 18, 1973) was an American psychologist who founded Harvard's Psycho-Acoustic Laboratory, studying psychoacoustics, and he is credited with the introduction of Stevens' power law. Stevens authored a milestone textbook, the 1400+ page "Handbook of Experimental Psychology" (1951). He was also one of the founding organizers of the Psychonomic Society. In 1946 he introduced a theory of levels of measurement widely used by scientists but criticized by statisticians.