The differences in the sensorimotor estimation of the Ponzo and Müller-Lyer illusions

Abstract

Assessment of visual geometric illusions with the use of hand movements was studied. The task specifications varied: movements were made by the right or the left hand, with or without visual control. At first the subjects had to remember the lines by passing their hands across the screen with the image of lines in the context of Müller-Lyer and Ponzo illusions and out the context of these illusions. Then the subjects had to reproduce the length of the segments on a blank screen with their eyes opened or closed. The obtained data showed the differences in estimations of Ponzo and Müller-Lyer illusions. The results revealed different levels of involvements of right and left hemisphere in the task and indicated different mechanisms of Ponzo and Müller-Lyer illusions development. The illusory effect in Ponzo illusion is absent during memorization (the first task) and become marked during reproduction (the second task). These results could be explained with peculiarities of processing the image on different levels of the visual system.