Stanley Smith Stevens (November 4, 1906 – January 18, 1973) was an American psychologist who founded Harvard's Psycho-Acoustic Laboratory and 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 often used by statisticians.