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Microsaccades drive illusory motion in the Enigma illusion
Journal Title
Proceedings of the National Academy of Sciences
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Publication Date
2008-10-14
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Publication Volume
105
Publication Issue
41
Publication Begin
16033
Publication End
16038
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Abstract
Visual images consisting of repetitive patterns can elicit striking illusory motion percepts. For almost 200 years, artists, psychologists, and neuroscientists have debated whether this type of illusion originates in the eye or in the brain. For more than a decade, the controversy has centered on the powerful illusory motion perceived in the painting Enigma, created by op-artist Isia Leviant. However, no previous study has directly correlated the Enigma illusion to any specific physiological mechanism, and so the debate rages on. Here, we show that microsaccades, a type of miniature eye movement produced during visual fixation, can drive illusory motion in Enigma. We asked subjects to indicate when illusory motion sped up or slowed down during the observation of Enigma while we simultaneously recorded their eye movements with high precision. Before "faster" motion periods, the rate of microsaccades increased. Before "slower/no" motion periods, the rate of microsaccades decreased. These results reveal a direct link between microsaccade production and the perception of illusory motion in Enigma and rule out the hypothesis that the origin of the illusion is purely cortical.
Citation
Troncoso XG, Macknik SL, Otero-Millan J, Martinez-Conde S. Microsaccades drive illusory motion in the Enigma illusion. Proc Natl Acad Sci U S A. 2008 Oct 14;105(41):16033-8. doi: 10.1073/pnas.0709389105. Epub 2008 Oct 8. PMID: 18843109; PMCID: PMC2572936.