An experimental comparison of stimulus and response translated power functions for brightness

A threshold parameter has been introduced into the power law in two different ways, one involving, translation on the stimulus axis (the Ф-Law) and the second involving translation on the response axis (the Ψ-Law). In this study the two laws were compared using the data from 6 Ss making magnitude estimation judgments of brightness. Although the prevalent view appears to favor the Ф -Lau, the data of this study clearly dictate a choice of the Ψ-Law over the $-Law for brightness.