If you stare at the center of this blur of colors below for long enough, the image will begin to disappear. The colors will start to fade away, whitening more and more, but as soon as you blink or think about it – it will all snap back into view. In other words, as long as you don’t think about the colors, it’ll reach the point the image becomes completely blank. But then if you take notice to what’s going on, the image will reappear as if nothing ever happened.
This optical illusion that popped up on r/woahdude Reddit is a variation of a visual trick called “Troxler’s effect.” However, many versions of it have existed since at least 1804! That was the year a Swiss physician, politician, and philosopher named Ignaz Paul Vital Troxler discovered the trick and why it happens. (Hence why it’s called the Troxler’s effect.) He went on to describe how it was that an image can fade away if you stare at it hard enough. In a nutshell, if you fixate your eyes on a certain point, stimuli near that point will gradually fade.
This mind trick – a phenomenon known as selective processing – is how your brain copes with the thousands of sensations it receives constantly. All extraneous information gets filtered out by the brain so that you can focus on the important stuff more easily. Any visual stimuli that doesn’t change will begin to get tuned out. It’s a natural built in defense mechanism.
In the case of the image above, when you focus on the center, your brain decides the unmoving shapes are unnecessary information (not a threat), and so it mentally “fills in” the space with the surrounding white – all to save you energy for what you really may need to focus on.
Normally, it is happening without you even realizing it because your eyes and your surroundings are constantly shifting, explained psychology professor Derek Arnold of the University of Queensland. It is not common for people to fix their attention on any one thing for very long which is why it is so rare for anyone to notice the phenomenon happening with visuals.
With that said, selective processing doesn’t only happen with what you see. It happens with all the senses and the other senses are more noticeable. For example: when you put on perfume and a minute or so later you don’t smell it anymore; or how soon after you put on your clothes you become unaware of the feeling of them on your skin.
