The perceptual set effects in the process of discrimination of objects

An experimental study is directed at the factors which can influence the process of discrimination of the stimulus. In the experiment the observers saw two objects which were different in size and had fixed positions on the screen relatively to each other. As a result, the observer had a perceptual set with the corresponding after-effect of contrast or assimilation illusion. It was found that discrimination process depends on the perceptual set after-effect. Besides, it was shown that the perceptual set could occur with objects that have illusory difference in size.