Evaluating a model of global psychophysical judgments for brightness: I. Behavioral properties of summations and productions.

Steingrimsson and Luce (2005a, 2005b, 2006, 2007) evaluated Luce's (2002, 2004) proposed psychophysical theory of loudness and found it substantially supported. The aim of the present research is to begin an extension of this research to brightness. Luce's (2002, 2004) theory deals with the global percept of subjective intensity, in which there is a psychophysical function Psi that maps pairs of physical intensities onto positive real numbers and represents, in an explicit mathematical way, subjective summation and a form of ratio production. These representations derive from a number of behavioral properties, including certain plausible background assumptions. In three experiments involving the subjective perception of luminance, brightness, the key behavioral properties of summation over the two eyes, and a form of generalized ratio production are empirically evaluated. Considerable support is reported for particular forms of Psi separately for summations and ratio productions.