On the possible psychophysical laws.

This paper is concerned with the centurv-old effort to determine the functiinal relations that hold between subjective continua and the physical continua that are presumed to underlie them. The first, and easily the most influential, attempt to specify the possible relations was made by Fechner. It rests upon empirical knowledge of how discrimination varies with intensity along the physical continuum and upon the assumption that jnds are subjectively equal throughout the continuum. When, for example, discrimination is proportional to intensity (Webers law), Fechner claimed that the equal-jnd assumption leads to a logarithmic relation (Fechners law). This idea has always been subject to controversy, but recent attacks upon it have been particularly severe. At the theoretical level, Luce and Edwards