Age-Related Differences in Perception of the Rotating Snakes Illusion Among Young and Older Adults with Normal Visual Acuity

Purpose: Visual illusions are utilized to elucidate mechanism of visual information processing. For example, the Rotating Snakes illusion creates the illusory perception of motion when viewing a static image. This study investigated the difference in perception of illusory rotation between younger and older adults with normal visual acuity. Participants and Methods: The participants included 105 younger adults (mean age: 23.7 years) and 100 older adults (mean age: 74.2 years). Each participant was presented with the Rotating Snakes illusion, then asked to respond whether they perceived the snakes to be "rotating" or "not rotating". The rate of perception of illusory rotation was compared between the two groups. To evaluate the effects of cataracts, a major age-related optical change, comparisons were also made between older participants with bilateral cataracts versus those with bilateral intraocular lens (IOL) implantation. Results: Rotation was perceived by 100% (105/105) of participants in the younger group, but only by 16% (16/100) of participants in the older group, showing a significant difference (p < 0.001). Among the older adults, the IOL and cataract groups had no significant difference in the rate of those who perceived the illusion (6/54 vs 10/45, p = 0.12). Conclusion: Significantly more younger adults perceived illusory motion in the Rotating Snakes illusion versus older adults. Lens opacity due to aging likely does not contribute to this phenomenon.