Abstract

Hermann Lotze (1817 – 1881) introduced the idea of retinal ‘Local Sign’ to explain the sense of visual direction, and proposed that the primary function of local sign is to direct overt and covert saccadic eye movements. Recent experiments have examined the relation between saccades and perceived visual direction. I shall describe two sets of interlinked experiments. In the first, saccades were made to virtual targets defined by points of imaginary intersection. These saccades showed biases similar in magnitude to perceptual effects in the Poggendorff figure. Second, saccadic adaptation was induced by shifting the target during the eye movement. With a target in a single visual direction, rapid adaptation took place so that the saccade landed near to the shifted target position, This adaptation does not occur under conditions of partial reinforcement and does not transfer to other directions. If training trials to several directions are interleaved, there is some adaptation to intermediate positions. We sought to see whether this ‘global adaptation’ would have perceptual consequences for perceived location of the saccadic adaptation in a body-centered frame of reference.

Biography Michael Morgan (http://www.staff.city.ac.uk/~morgan/) studied Experimental Psychology in Cambridge (1964) and subsequently held Chairs in Psychology at Durham and University College London;, and in Neuroscience at the Universiy of Edinburgh. He is currently Professor of Visual Neuroscience at City University (Optometry) and a Max-Planck Senior Fellow a the Institute for Neurological Research in Cologne. He is the author of ‘Molyneux’s Question’ (1977) and ‘The Space Between Our Ears’ (2005).