BRIGHTNESS CONSTANCY IN A GANZFELD ENVIRONMENT

In this paper, experiments are described in which brightness constancy was studied in a Ganzfeld environment. Luminance variation by means o f neutral density filters was applied to stimuli consisting of a Ganzf eld with superimposed disks. To this end, a special-purpose apparatus was constructed. Sequential dichoptical brightness matches with a refe rence stimulus were carried out for the disks as well as the homogeneo us surround. The results of these measurements indicate that (1) besid es a clear tendency toward brightness constancy, small but systematic effects of the average luminance level are present and (2) the brightn ess of the Ganzfeld is hardly affected by the presence of the disks. F inally, it is shown that the experimental results can be modeled adequ ately in terms of a concept that involves an accumulation of contrast information.