The Fraser-Wilcox illusion is a type of optical illusion in which a physically static image appears to be moving. An example of the illusion is shown in the figure below. The two wheels are expected to induce illusory rotation in clockwise and counterclockwise directions, respectively. The illusory motion direction is modified by flipping the order of the 4 shades that are used to construct the patterns. The illusory motion can also be cancelled by injecting physical motion in the opposite direction.
The perceived speed of the illusory motion is dependent on both how the visual stimulus is constructed (see http://www.ritsumei.ac.jp/~akitaoka/index-e.html for more variants of the illusory motion stimulus) and on the person observing the stimulus. In our recent paper, we investigated why different people see different illusory motion speeds. Perceived illusion strength is quantified by the speed of the physical motion that cancelled the illusory motion for each participant. Our results suggest that individuals with better ability to discriminate between different contrasts tend to perceive faster illusory motion. Individual sensitivity to the speed of physical motion was not associated with illusory motion strength.
Our study also explored whether self-reported daily visual discomfort in people with migraine is related to motion illusion strength. We found that motion illusion strength is not different between people with migraine and headache-free control groups. Motion illusion strength was also not associated with susceptibility to daily visual discomfort, suggesting that motion illusion strength is not a surrogate indicator of visual discomfort in migraine.
Link to the full article: https://iovs.arvojournals.org/article.aspx?articleid=2770529
The experiments described in this paper were performed as part of Chongyue He’s Master of Philosophy research project.
Clinical Psychophysics Unit, Optometry & Vision Sciences, University of Melbourne 