A structural analysis of stability in the perceived form of objects rotating in depth

Summary The stability and form of the two different appearances of a simple rotating object were explained by considering both the geometric transformations interrelating these appearances and their degree of organization. The analysis was then used to guide the construction of two complex rotating objects each expected to have multiple appearances. The results of an experiment confirmed the predicted form of the objects' initial appearances (illusory), the relative stability in time of these appearances and the form of the subsequent appearances (also illusory). The veridical appearances were never seen despite continued observation during two 10 min periods.We wish to thank P. Hamilton, A. Pearsall, A. Vadum, and H. Vadum for their help with this research. Requests for reprints should be sent to the first author at 1 Howatson Way, Worcester, Massachusetts, 01609, USA