2008 Volume 8 Issue 1 Pages 175-183
In this study, the cognition process of Müller-Lyer illusion was studied by electroencephalogram (EEG). Müller-Lyer illusion (ML illusion) is a famous geometrical illusion. In the ML illusion, the length of the shaft is overestimated when it forms wings-out (i.e., >-<) and underestimated when it forms wings-in (i.e., <->). ML illusion is frequently thought as an optical illusion because it is assumed that such an illusionary effect could be brought from its geometrical construction in terms of depth perception. However, number of behavioral studies showed that the ML illusion could be taken place not only in vision but in touch (haptic illusion). Moreover, it gives the same length miss-estimation effects to the subjects who are congenital and acquired blind. Thus, somehow, higher information processing than the optical processing in the brain is expected to be involved in the cognition of ML illusion. We investigated visual evoked potentials (VEPs) under subjects' perceiving ML illusion and non-illusionary figure (i.e., I-I) by 256chigh-resolution electroencephalography. As a result, we found a marked difference of evoked potentials between ML condition and control condition. Because such differences were more remarkable around the midline of the parietal brain where the multi-modal perception information was thought to be integrated, this result suggests that some higher information processing than the optical one in the brain might be involved in the cognition of ML illusion.
