Physiological optical illusions
Disappearing dots
A Hermann grid is a famous optical illusion leaving the observer playing an impossible game of chase the dots. Scan your eyes over these black squares and take notice of the areas where the white lines cross. Can you see grey dots in your peripheral vision? Though they are scattered across the intersecting lines, as you focus on a single dot you will witness it disappearing. These dots were never really there, but made up by your eyes.
Contrast
The circles you see appearing and disappearing between the squares are due to the difference in lightness between the black and white areas. These dots are grey in
