Cognitive Functions Influence Lightness Perception

Lightness research offers ample evidence that visual scene contains all the cues necessary to perform lightness calculations. In real life, contrary to laboratory findings, familiarity of the objects seems to be more important than the temporarily viewing conditions. In our experiment observers were led to believe that they see the same object moving from one illumination to the other. The estimated shade in the second illumination varied as a function of the shade in the first illumination. In the second experiment, object identity was stressed by the introduction of targets with distinct geometrical shape. Subjects were familiarized with these targets and under the impression that those targets were the only targets used, even after illumination and background changed. Consequently, their matches corresponded to memorized and not viewed shade. In the third experiment observers were familiarized with two sets of targets. Only one set was used in the experiment, but twice, with different instructions. The targets were estimated based on the instruction mentioning the set from which the target presumably was taken. Nevertheless, imagery did not aid the process. When the observers were asked to keep imagining the gray shade they were previously observing, the lightness estimation depended exclusively on the factors presented in the visual scene. However, memory overpowers viewing condition. In the last experiment, observers were shown the same object in two illuminations simultaneously but were asked to estimate lightness when the object was removed from view. The value of this match-from-memory was in between the values for the two illumination levels