Perception of eye scans with the Müller-Lyer stimuli: evidence for filter theory

Ginsburg's filter theory successfully accounts for the perceptual distortions perceived in a wide range of illusions and bistable phenomena. Essentially, the theory proposes that illusory distortions are the natural consequence of low-pass spatial filtering (based upon the human modulation transfer function) of the physical stimulus. With regard to the Müller-Lyer illusion, predictions based upon filter theory and human scan-path data are in accord. However, data linking filter theory's predictions regarding perceptual experiences associated with the illusion to the eye-scan results have been missing. In the present experiment subjects provided subjective estimations of their own eye scans while viewing each of the following stimuli: the fins-out member of the Müller-Lyer illusion, the fins-in member of the Müller-Lyer illusion, and a finless horizontal line (variations of each stimulus consisted of one, two, and three line segments). The analysis of these data supported three predictions that were derived from filter theory. Potential problems facing filter theory are also addressed.