Brightness Illusion Induced by Consistency Constraints

We present a novel brightness illusion (the ‘Brick Illusion’) that is determined by perceptual interpretation. The image is ambiguous in terms of depth layering, and the strength of the illusion depends on the chosen interpretation. When a certain interpretation is enforced by stereo disparity, and the layering is disambiguated, the strength of the illusion changes according to constraints on the consistency between depth layering, transparency relationships, and surface brightness.

We applied a 2AFC brightness comparison procedure to quantify the strength of the illusion. This procedure allowed us to measure the uncertainty of judgements on relative surface brightness in illusory conditions. The increased uncertainty of our observers among these conditions reflects the multidimensional nature of these judgements.

This paper is linked to the following World Wide Web page: http://zeus.rutgers.edu/∼feher/brick.html. With a Java-enabled browser the reader can change the gray levels of the backgrounds and the disks, the disparity of the disks, and other parameters.