title: There and back again: revisiting the on-time effect.
abstract: In apparent motion, static stimuli presented successively in shifted locations produce a subjective percept of continuous motion. Reducing stimulus exposure (or on-time) was shown to consistently increase the perceived velocity of apparent motion (Vision Research 29 (1989), 335-347), yet surprisingly little investigation has followed up on the discovery of this illusion. In five experiments, we delineate the boundary conditions of the on-time illusion in order to clarify its underlying mechanisms. Subjects viewed multi-item apparent-motion displays, in which at some point, on-time duration either increased or decreased. Objective velocity remained unchanged, yet participants had to judge whether they perceived the motion to become slower or faster. We observed the on-time illusion during both fast and slow apparent motion. The effect was not modulated by stimulus luminance, thus precluding an energy-summation account of the illusion. It generalized from speed perception to time perception in a temporal bisection task. The illusion was specific to apparent motion, as it did not occur with veridical motion. Finally, the illusion persisted when on-time and off-time were not confounded, that is, when off-time remained constant. These findings are discussed in the framework of current models of motion perception.
authors.affiliation: School of Psychological Sciences, Tel Aviv University, Tel-Aviv, Israel. Electronic address: alonzivo@post.tau.ac.il.
authors.forename: Alon
authors.initials: A
authors.lastname: Zivony
authors.affiliation: School of Psychological Sciences, Tel Aviv University, Tel-Aviv, Israel.
authors.forename: Dominique
authors.initials: D
authors.lastname: Lamy
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013997:Time Factors; D013998:Time Perception / Q000502:physiology*; D055815:Young Adult
keywords: Apparent motion; Motion perception; Velocity perception; Visual illusion