The differences of perception of Muller-Lyer and Ponzo illusions at sensorimotor measurements V Karpinskaia, V Lyakhovetskii |
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Pavlov Institute of Physiology RAS, Saint-Petersburg State University, Russian Federation
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| There is some evidence of changes in the strength of visual illusions at different stages of schizophrenia compared with normal adults. Other results show that the strength of visual illusions is strongly dependent on both the modality of reproduction and handedness in a haptic version. In the present experiment, the Müller-Lyer and Ponzo illusion figures were presented to volunteers on the touch screen in separate trials. Using the index finger of his/her right- or left-hand, the volunteer’s task was to trace along the two shafts (Müller-Lyer ) or lines (Ponzo) in an initial memorization stage. The illusion figure was then blanked on the screen and the volunteer had to reproduce the shafts or lines from memory using their finger on the touch screen. In this reproduction stage the volunteer’s eyes were either open or closed. The results revealed that there was a significant haptic Müller-Lyer illusion during both the memorization and reproduction stages. In contrast, there was only evidence of a haptic Ponzo illusion during the reproduction stage. The magnitude of both illusions was higher when the volunteer’s eyes were closed. These results support the hypothesis that different factors or mechanisms are responsible for these two well-known visual illusions. |
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