Stare at the red cross without moving your eyes. Within seconds, the colored blobs fade into the background.
Try this
- Hold your gaze steady on the cross for 10 to 20 seconds.
- Make the blobs sharper with Softness of the blobs: sharp edges resist fading.
- Blink or move your eyes and the blobs come straight back.
Why it happens
Ignaz Paul Vital Troxler described it in 1804. Your visual system responds to change; anything unchanging in your side vision, especially with blurry edges, gets filtered out. Normally, tiny eye movements called microsaccades keep refreshing the image. Susana Martinez-Conde and colleagues showed that microsaccades counteract this fading: when people made fewer of them, things faded more.
Did you know?
This filtering is why you do not notice the blood vessels lying in front of your own retina.
References
- Martinez-Conde S., Macknik S., Troncoso X., Dyar T. (2006). Microsaccades Counteract Visual Fading during Fixation. Neuron, 49, 929. doi:10.1016/j.neuron.2006.02.007
- Background on Wikipedia
The illusion on this page is drawn by code written for this site. Last checked 1 November 2026.
Frequently asked questions
Why do the blobs disappear?
Your visual system tunes out unchanging, blurry things in side vision unless tiny eye movements refresh them.
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