How many black dots can you count between the squares below?
It simply can’t be done! Every time your eyes move or your focus changes, you see that the dots in the center of your peripheral field are in fact white, while the ones along the peripheral edges seem to show up as black.
So what explains the appearance of these black dots? Our visual system is cued to process edges of objects as this enables our brains to properly define and interpret them. As a result, this sometimes leads to visual deceptions that distract from the center of our field of view, such as the black dots we experience in the Hermann grid!