Optical Illusions

(Graphics are courtesy of Wikipedia)

Physiologic illusions are based on release from a strong visual stimuli of brightness, color, movement, etc.

Contrast and contrast inhibition make us see black dots at the intersecting lines.

If you stare at this picture for 60 seconds and then look away, you will see an afterimage with the colors reversed,

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Cognitive illusions are a result of our mind making incorrect assumptions about our visual stimuli.

Figure-ground constancy reversals allow us to see 2 faces or a vase

In real life experience parrallel lines appear to converge over distances.

Although both yellow bars are the same size the farther bar appears wider.

Our mind fills in the missing lines and we perceive what we expect to see.