Stochastic processes in reversing figure perception

The timing patterns of figural reversals were measured, using a stimulus figure usually seen in one of two well-defined forms. The figure was a three-dimensional surface formed by denting a flat piece of Plasticene with a table tennis ball. The surface thus formed could be seen as dented or as bubbly. Transitions between the two forms were clear and abrupt and could not be voluntarily controlled by even a practiced O. The timing distributions of reversals, for four Os who worked for five sessions of 36 min each, were found to be incompatible with theories based on satiation-like effects; neither did they conform with a simple random-walk model. A random-walk model based on a finite majority decision device with memory was found to describe the data better than either. Data from 20 90-min observation periods for each of two Os were analyzed in detail according to this model, and it was found that the gross behavioral changes that sometimes occurred from period to period could usually be accounted for by a change of exactly one unit in one or another of the three parameters of the majority detector. The mathematical description of the model is given in a separate appendix to the paper.