Figure 3. Adelson’s visual trap.
In this cognitive trap, two pairs of boxes are compared without (A) and with masks (B, C) to demonstrate how the brain is tricked into seeing boxes of equal intensity as different intensity (C). The image in D displays an image-analysis markup where boxes have been colored by intensity (i.e. all red boxes are the same intensity, etc.). Adapted from Adelson, EH, Lightness Perception and Lightness Illusions. In The New Cognitive Neurosciences, 2nd Edition. MIT Press (2001)