Oxnard - Port Hueneme Optometry Dr. Don Steensma 465 W. Channel Islands Blvd, Port Hueneme, CA 93041 805/486-3585
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.
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.