Abstract
Mruczek et al (2015) showed that a dynamic version of the Ebbinghaus illusion almost doubles in strength compared to the standard version. In their dynamic version, the size of the surrounding inducers was modulated between large and small over about 1 second and the whole stimulus was also made to drift during the surround modulation. We explored many simultaneous contrast and geometric illusions and found no increase from dynamic presentation in any that we sampled. Here we report only the results for simultaneous orientation contrast and Müller-Lyer and surprisingly, when these two illusions were presented dynamically, their effects were actually eliminated. It is not yet clear why only these Ebbinghaus illusion increases with dynamic presentation. We offer the same explanation that Mruczek and colleagues proposed (2015) – with static presentation, information about actual size and position accumulates from the receptive fields at that location. When the illusion figures are dynamic (moving or flashed), however, individual receptive fields cannot accumulate the corrective information and the illusion strength is less constrained. This hypothesis does not account for why orientation contrast and the Müller-Lyer illusions are eliminated as opposed to amplified.