Interactions of Monocular and Cyclopean Components and the Role of Depth in the Ebbinghaus Illusion

Abstract

A study of size interactions of objects in three-dimensional space is reported. The canonical form of the Ebbinghaus illusion—test circles surrounded by large or small inducers—was used. Both monocularly visible (M) and purely cyclopean (C) objects were displayed stereoscopically to isolate the monocular and cyclopean components of the illusion. The results of two experiments indicate that: (i) depth plays a significant role when the test circles are cyclopean, but not when they are monocularly visible; and (ii) the size of C objects is affected equally by C and M inducers, but the size of M objects is affected much more strongly by M than by C inducers. In conclusion, possible explanations are offered for the main trends in the data, the most interesting of which is that cyclopean tests seem to be interacting only with the cyclopean component of monocularly visible inducers.