GEOMETRIC ILLUSIONS

The effects of instruction and training on the magnitude of illusion were investigated using as stimuli Müller-Lyer, Müller-Lyer-Ebbinghaus, and Oppel's figure, and a perspective illusion. The subjects estimated the difference between the standard and the variable. The results suggest that changes in judging attitudes, and perceptual learning, contribute to the decrement of illusion during repeated presentation; adaptation to a two-dimensional stimulus world seems to affect the size of illusions which can be explained on the basis of constancy theory. The interactions between the treatments were fairly high.