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« Cognitive Brown Bag Talk | Main | Proceedings of SULA 3 hit the (virtual) shelves!»

Five College Cognitive Science Seminar

Alan Gilchrist
Rutgers University

Computation of surface lightness in simple and complex images

Monday, April 30, 3:30 pm, School of Management Room 133

Abstract

No computer program exists that can merely identify the white, black, or gray shade of surfaces in an image. Human lightness perception is the only proof that it can be done at all, but we don’t know how the human system works. We do know how lightness is computed in the simplest possible image that can produce the experience of a surface, that is, two adjacent gray shades that fill the observer’s entire visual field. We create such an image by placing the observer’s head inside a large hemisphere the interior of which is painted with two shades of gray. The lighter half always appears white while the lightness of the darker half depends on the luminance ratio between the two halves. But what about complex images? It appears that each region of illumination (called a framework) within a complex image functions like one of our simple hemispheric images, except that one additional principle is needed. Kardos (1934) called it co-determination. Computations are not done exclusively within a framework; there is a specific form of crosstalk between frameworks, which will be described. This new conception accommodates a wide range of data in lightness perception, especially the specific patterns of errors humans make.

April 26, 2007 12:05 AM | 05:12 (2007-04-26) , events