title: Modelling stereokinetic phenomena by a minimum relative motion assumption: the tilted disk, the ellipsoid and the tilted bar.
abstract: The stereokinetic phenomena of the tilted disk and of the ellipsoid are visual illusions of depth elicited by a flat figure with elliptic contour rotating at uniform speed in the frontal plane of an observer. Strictly related to the appearance of the ellipsoid is the stereokinetic phenomenon of the tilted bar, elicited by a line segment of constant length rotating at uniform speed in the frontal plane. We present a mathematical model of these phenomena, based on an assumption of minimization by the Visual System of the differences between the lengths of the velocity vectors of the stimulus (minimum relative motion assumption): the "rigidity hypothesis" is able to explain the appearance of the tilted disk but not the appearance of the ellipsoid and of the tilted bar. The theoretical results obtained by our modelling are in good agreement with the experimental observations.
authors.affiliation: Dipartimento di Matematica Pura ed Applicata, Università di Padova, Via Trieste 63, Padova, 35121, Italy. beghi@math.unipd.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Beghi
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Xausa
authors.forename: Mario
authors.initials: M
authors.lastname: Zanforlin
mesh_terms: D003867:Depth Perception / Q000502:physiology*; D008433:Mathematics; D008962:Models, Theoretical; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D009903:Optical Illusions; D013499:Surface Properties