A method to assess the relative contribution of lateral inhibition to the magnitude of visual-geometric illusions

Observer errors of judged length when viewing the Müller-Lyer illusion arise partially from distortions caused by lateral neural interactions in the retina. To assess the relative contribution of such lateral neural interactions to the total magnitude of the illusion, the Müller-Lyer figure was presented to observers under a form of intermittent-light stimulation that enhances lateral inhibitory activity. In Experiment 1, intermittent-light conditions produced the largest increase in illusion strength for the standard variant of the Müller-Lyer figure but not for a dot form in which contour interactions are minimized. The results of Experiment 2 showed that the hypothesized lateral inhibitory contribution varied as a function of wing-shaft angle. In addition to confirming the contribution of lateral neural interactions to illusion formation, these findings also suggest that exposure of illusion configurations under intermittent illumination may provide a method of determining the relative contribution of lateral inhibition to illusion configurations other than the Müller-Lyer.