Why are we surprised by only some of the things we see? Spatial contrast, color contrast, and visual illusions


Dr. Arthur Shapiro

The visual response to color is often thought to be slow (typically, chromatic modulation thresholds are about eight times higher at 10 Hz than at 1 Hz). Recent studies, however, have shown that the visual system can adapt perfectly well to fast chromatic contrast (> 10 Hz) and that cells in cortical area V1 respond to fast chromatic contrast modulation. To investigate this apparent discrepancy, my laboratory has developed a class of stimuli based on shifting the temporal phase of multiple sources of contrast information ( http://journalofvision.org/8/1/8/). This class of stimuli makes it relatively easy to separate the visual response to color (1st-order information) from the visual response to color contrast (2nd-order information). Examples of this stimuli can be seen at www.shapirolab.net. In this talk, I will show how this finding leads to a new quantitative model of color vision that contains a separate contrast channel. I will then show how this model can be used to generate new and compelling visual “illusions” that can be informative about many aspects of visual processing and can lead to new ways of approaching real world problems.

Arthur G. Shapiro. B.A. (U.C. San Diego, Math/Psychology). Ph.D. (Columbia, Psychology), Post-Doc (U. Chicago, Vision Science). My research is in the area of visual perception. I use psychophysical techniques to investigate low-light-level vision, motion, visual camouflage, and image contrast in color vision. I am perhaps best known for creating a series of visual illusions that have arisen from this research. Some illusions produced in my laboratory have won awards in international contests held in conjunction with major vision science conferences (see www.shapirolab.net).