Classical visual phenomenology revisited: Ken Nakayama, Adjunct Professor, Department of Psychology, UC Berkeley
Colloquium | November 28 | 5:15-6:15 p.m. | 1104 Berkeley Way West
Ken Nakayama, Adjunct Professor Department of Psychology UC Berkeley
We have all seen Jastrows Rabbit Duck, Rubins face-vase, the reversing Necker cube as well as the Kanizsa triangle. These images have graced elementary psychology textbooks and pop science books alike. Yet they have remained as memorable curios without influencing mainstream thinking as to how the visual system operates. Maybe its because visual science has gravitated to more objective measures, using sophisticated psychophysical methodology. However, we argue here that some of the oldest perceptual demonstrations, especially the century old Rubin Face Vase and the subjective contours of Kanizsa figures, supplemented by newer demonstrations from my group, are unusually revealing as to fundamental visual processing. In particular Rubins figure-ground takes on a more modern interpretation, reflecting changing border ownership signals. These signals delineate the bounding (occluding) contours of surfaces and objects in 3-D scenes. Such border ownership signals have been shown in primate visual area V2 by Rudiger von der Heydt and colleagues. Our claim is that perceived subjective contour strength constitutes a direct readout of border ownership neuronal firing. As such, perceptual phenomenology itself provides a powerful way to track specific neuronal populations which are involved in signally bounding contours of surfaces and objects, furnishing a unique and readily available subjective bioassay. With this, we show that relatively that low level rather than high level visual patterns are operative, consistent with bounding contour assignment occurring in relatively early retino-topic cortex.