Troxler’s fading, also known as Troxler’s effect or Troxler’s fading circle, is a phenomenon of visual perception named after Ignaz Paul Vital Troxler, a Swiss physician and philosopher who first documented the effect in 1804.

The effect occurs when you fixate your gaze on the little red dot at the center of the blue ring for an extended period (usually about 20 seconds or more). When this happens, stimuli in the peripheral vision area that are unchanging or have a consistent pattern begin to fade away and eventually seem to disappear. This happens because your visual system essentially “tunes out” the unchanging stimulus, a phenomenon referred to as neural adaptation or sensory adaptation.

Troxler’s fading is a potent demonstration of how our brains process visual information. It’s not just about the light that hits our eyes; it’s about how our brain interprets that information and continually adapts to the environment.

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