Measuring motion illusion strength in op art paintings

JM Zanker, U Leonards

Research output: Contribution to conferenceConference Abstractpeer-review


Using simple black and white patterns, Op artists create vivid sensations of movement which spawned a lively scientific debate about visual processing mechanisms underlying motion illu- sions in static images. Recent studies point in the direction of a rather simple account in terms of involuntary eye movements, which lead to characteristic motion interference patterns (Zanker and Walker, 2004 Naturwissenschaften 91 149 ^ 156). We developed a new method to quantify the strength of the illusion for synthetic `riloids' that were inspired by some of Bridget Riley's paintings, to replace the unreliable rating scale used previously. Observers compared in a 2AFC paradigm the motion sensation for a given test stimulus with that for a set of reference stimuli, which were combinations of a riloid and a checkerboard pattern at different contrast ratios. The dominance of the riloid in the compound pattern led to a strong motion illusion, whereas a dominating checkerboard led to a static percept. The continuous variation of illusion strength between these two extremes is utilised to generate psychometric functions, which allow us to compare the illusion strength for different test stimuli. A pilot study of this method found no clear differences between observers suffering from migraine and controls.
Translated title of the contributionMeasuring motion illusion strength in op art paintings
Original languageEnglish
Pages237 - 237
Number of pages1
Publication statusPublished - 2006


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