Dependence of perceived purity of a chromatic stimulus on saturation adaptation

The purpose of sensory adaptation of the visual system is to adjust sensitivity of the photoreceptors to optimize the dynamic range of response of the visual system. It has been shown in numerous research papers that chromatic adaptation influences both color appearance and color discrimination. However, there are almost no studies in which the influence of chromatic adaptation on perceived purity has been investigated. Therefore, the aim of this study was to investigate how chromatic adaptation to stimuli with certain saturation influences perceived purity of test stimuli with the same hue but different saturation.

As the stimuli were modulated in saturation only, we refer to the type of chromatic adaptation used in our study as saturation adaptation. Two types of psychophysical methods - the method of adjustment and the method of constant stimuli - were used.

The results obtained with the method of constant stimuli reveal that saturation adaptation seems to be nonlinear much the same way as the Bezold-Brücke and the Abney effect. In addition, hysteresis of saturation adaptation can be observed in the method of adjustment.

Pronounced hysteresis of perceived color purity was observed when approaching to the point of subjective equality from the side of low saturation of the matching stimulus compared with the side of high saturation of the matching stimulus. There was a time course of mechanisms of saturation adaptation similar to those of chromatic adaptation previously quoted in literature.