Abstract
In exploring different illusory contours, we have come across several cases that seem to resist a simple unifying explanation and do not easily fit current explanations. For example, one arrangement yields strong illusory contours when circles are the stimuli, but no effect when comparable squares are used. Similarly, brightness assimilation-like illusory contours result in conditions in with some inducing stimuli but not others that would seem comparable.
In addition we have been exploring illusory contours with inducing stimuli that are very different from those traditionally used. The work is a mix of exploration and the systematic assessment of some factors involved.
The work offers new possibilities, but also raises questions about illusory contours.