A Short Method for Calculating the Adaptation-Level for Absolute and Comparative Rating Judgments

Abstract

Extension of the theory of adaptation-level (AL) to include comparative as well as absolute types of judgments has enlarged the sphere of use of equations previously published by Helsonl and by Michels and Helson2 for quantitatively evaluating factors which influence psychophysical and other types of judgment. Calculation of the best value of AL and of the weighting constant, b, which measures the relative contributions of the stimulus-series and of the AL in determining responses to stimuli, can be shortened considerably when using the method of least squares through the use of tabulated values of the function Y = (0.5K+J) / (1.5K-J) which enters into Helson's equation.3 In this article two examples are presented illustrating use of tabulated values of Y as a function of the judgments (Table I) and of coded stimulus-values (X') to minimize the computations in solving the normal equations for the desired constants. Data obtained by the method of 'absolute judgment' and by the method of comparative ratings4 have been chosen for the worked examples in order to demonstrate application of the equation to two different scales of categories involving two psychophysical methods.