You've all seen the visual illusion consisting of a matrix of black squares separated by white lines running vertically and horizontally, separating all the squares. There appear to be fuzzy little black dots at the intersections of the white lines. This is usually explained in terms of lateral inhibition. Lateral inhibition is also used to explain the phenomenon of Mach bands. But one of my colleagues pointed out that in the matrix illusion, when you look directly at an intersection you don't see the illusory dots. It seems that they don't appear in foveal vision, but only in peripheral vision. But this doesn't hold true for Mach bands; they don't seem to change whether viewed foveally or peripherally. What's up with that? ---------- Patrick S. Williams Department of Social Sciences University of Houston-Downtown Houston, TX 77002 713-221-8982
