ABSTRACT Visual illusions involving distortions of apparent length, size, and direction have been shown to be caused by both peripheral (physiological) and central (psychological) factors. Peripheral components include lateral inhibitory interactions or blurring due to optical aberrations. Central components include distortions from learned patterns of information sampling and cue utilization. With continued inspection, many illusions show diminished magnitudes. It is suggested that this phenomenon of illusion decrement may be used to ascertain the relative contributions of central and peripheral components. In addition, a discussion of the possible implications of illusion decrement for the understanding of the mechanisms involved in perceptual distortions is included.
Girgus et al. (Sun,) studied this question.