Apparent reversals seen by three types of perceiver of the Ames trapezoid illusion.

Three groups of subjects (three right-handed, right-eye-dominant men in each group), differing in the overall extent to which they perceived illusory oscillation with Ames's rotating trapezoidal window, were tested for their susceptibility to parameters of the illusion previously shown relevant in unselected samples. Differential response of these three perceiver groups to variations in viewing distance and target form was demonstrated; but target pattern produced no significant effects. It was concluded that consideration should be given to the distribution of these perceiver "types" in samples taken to study illusions of oscillatory motion.