Freaky Friday Files: Troxler's Fading
- Ash
- 8 hours ago
- 3 min read
Hi friends! Happy Fri-YAY! For this week's edition of Freaky Friday Files, I thought we could take a look at Troxler's Fading (also known as the Troxler Effect). I also briefly talk about the Caputo Effect.
Reader discretion advised.
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Troxler's Fading
According to Wikipedia, Troxler's Fading "is an optical illusion affecting visual perception. When one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point will fade away and disappear. Research suggests that at least some portion of the perceptual phenomena associated with Troxler's fading occurs in the brain." Troxler's Fading was first identified by Ignaz Paul Vital Troxler (1780 - 1866), a Swiss physician, politician, and philosopher, in 1804.
Kanai & Kamitani (2003) explain Troxler's Fading as follows: "After prolonged fixation, a stationary object placed in the peripheral visual field fades and disappears from our visual awareness, especially at low luminance contrast". An example of Troxler's Fading is an animated GIF of a circle of purple dots around a central cross. If you focus long enough on the centre, one dot disappears or turns green. This effect occurs because our brains stop responding to stimuli that do not change in our peripheral vision.
Here's an example YT video if you want to try it out! I did it, and when you're staring at the black dot, everything fades away, but if you look away for a slight second, the coloured dots come back. Isn't that crazy?! Brains are cool.
In 2010, a study was conducted where subjects stared into mirrors with dim lighting for 10 minutes. About 2/3rds of subjects saw their faces distort, 1/2 saw monsters, and more than 1/4 of subjects saw an unfamiliar person staring back at them. The reason for this is that your brain is fading out parts of your face you are not directly focusing on. Therefore, the brain fills in information with either stored images or fears (Caputo, 2010). This is often dubbed the Caputo Effect and is similar to Troxler's Fading. Some scholars argue that they are the same, and others argue that they are different. It's definitely in the same realm of perception/cognition, in my opinion. And to be clear, you need to stare at your face for at least 10 minutes for anything to happen, so normal mirror checking isn't likely to cause anything super scary. In contrast, it doesn't take very long for Troxler's Fading to kick in.
To help understand this phenomenon of Troxler's Fading, the brain is designed to prioritise "new" and changing stimuli/information, e.g., a predator in grass, but ignores "old" boring stimuli to conserve energy. When you stare at something like the black dot, the brain gets bored with the images around it, so it filters them out. It's similar to how we can always see our nose, but our brain doesn't pick up that it's there. The brain stops receiving updates about the "boring" stimuli, and so it fades away. Troxler's Fading works best in one's peripheral vision, as this part of the eye has less detail-focusing abilities and relies on larger receptive fields. Neural adaptation in the brain occurs to make things "fade away".
Troxler's Fading is a form of multistable perception ("a perceptual phenomenon in which an observer experiences an unpredictable sequence of spontaneous subject changes"). For example, the duck-rabbit image is a form of multistable perception. Troxler's Fading also has similarities with motion-induced blindness.
Have you ever experienced the Troxler Effect before? Have you experienced the Caputo Effect while staring in the mirror? Let me know what you saw!
Thank you for reading!!
Stay safe,
Ash x
References
Bonneh, Y. S., Donner, T. H., Cooperman, A., Heeger, D. J., & Sagi, D. (2014). Motion-induced blindness and Troxler fading: Common and different mechanisms. PLoS One, 9 (3), e92894.
Caputo, G. B. (2010). Strange-face-in-the-mirror illusion. Perception, 39(7), 1007.
Devyatko, D., Appelbaum, L. G., & Mitroff, S. R. (2017). A common mechanism for perceptual reversals in motion-induced blindness, the Troxler effect, and perceptual filling-in. Perception, 46(1), 50-77.
Kanai, R., & Kamitani, Y. (2003). Time-locked perceptual fading induced by visual transients. Journal of cognitive neuroscience, 15(5), 664-672.
Simons, D., Lleras, A., Martinez-Conde, S., Slichter, D., Caddigan, E., & Nevarez, G. (2006). Induced visual fading of complex images. Journal of vision, 6(10), 9-9.
https://listverse.com/2025/07/23/10-complex-psychological-mysteries-of-the-mind/
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