Prof. Michael Morgan – Vortragsexposé – Wintersemester 2010/2011

FORSCHUNGSKOLLOQUIUM DES PSYCHOLOGISCHEN INSTITUTS

Das Psychologische Institut und das Studium generale laden zu folgendem Vortrag ein:

Prof. Michael Morgan

(City University of London / Fellow am Max-Planck-Institut für neurologische Forschung, Leiter der Arbeitsgruppe "Visuelle Wahrnehmung" in Köln)

The Explanation of Visual Illusions

Mittwoch, 17. November 2010, 16.15 Uhr, Hörsaal 01-211

Psychologisches Institut, Binger Straße 14–16, 55122 Mainz



The classification of certain visual phenomena as 'illusions' is based on the naïve realist view that normal visual phenomena are 'veridical'. The realist view does not survive rigorous scrutiny. The history of Vision Research shows that phenomena are called 'illusory' when they depend upon limitations of the visual system that are poorly understood at the time. For example, the phenomenon of colour metamerism was considered an illusion until it was understood as an inevitable consequence of trichromacy. 'Moving Pictures' were considered an illusion in the early years of cinematography, but are now understood as a consequence of the limited temporal frequency response of human vision. A large class of 'illusions' such as the Barber’s Pole and the Fraser twisted cord arise from the limited spatial range of low-level filters in the visual system. Others depend on the limited spatial frequency bandwidth of filters.

The class of 'illusion' most recalcitrant to the foregoing analysis are the geometrical illusions such as the Muller-Lyer. In this talk an attempt will be made to explain these phenomena by the counter-intuitive inability of the visual system to deliver certain computations of length and angle.

Demonstration (to be discussed): Looking at the image (http://www.staff.city.ac.uk/~morgan/RI_Poster.pdf), move your head backwards and forwards to see the rings rotate around Exner’s head.