Optical tricks

We see optical illusions daily. Internet users post optical illusions for amusement. These illusions can occur spontaneously or be produced by painters and illustrators.


For some reason, optical illusions seem to show us something that isn't. What’s happening? 


Unlike a camera or computer, our vision system does not produce consistent images. It's live tissue that changes with the environment.   


Scientists are not entirely certain why we experience optical illusions, but these are some of their theories: 


Why does the vision system produce optical illusions? 

Retinal nerves are activated by light passing through the cornea and lens. The optic nerves carry visual information to the brain's visual center. Complex and unknown systems convert visual information into eyesight in the vision system. It's well acknowledged that brain circuitry creates optical illusions. 



The vision system continuously perceives light, color, distance, dimensions, and other characteristics. Some combinations of these variables confound the visual system and distort vision. Water bends light, so a fish in a pond appears elsewhere.   



Early humans needed quick threat recognition to survive in a hazardous world. A leopard could eat them for lunch if they didn't act fast. This urge for speed may cause optical illusions.  



Simple patterns of lines, dots, and hues can confound our brains' perceptions. The Checkershadow Illusion, invented by an MIT researcher in 1995, shows how the brain misinterprets visual cues. Slight changes in brain perception of hues, forms, edges, and lighting contrast. This doesn't indicate brain dysfunction. Instead, the brain strives to draw the best conclusion from conflicting data.


Optical illusion in drawings: Illustrations faking us out

Pictures might show two things depending on your perspective. Depending on your brain's first impression, Young Woman or Old Woman will appear. When you swap images, a “gestalt switch” occurs. After seeing the second image, the first is hard to see again. 


Optical illusion in pictures: Fun with double vision 

This strawberry image shows the brain filling in missing information. A Japanese researcher eliminated all red pixels from this strawberry photo. Strawberry color remains red. How is this possible? Traditional color photos have red, blue, or green pixels. If the red pixels are gone, as in this image, the brain can connect blue and green images with our expectation of red strawberries. Results: Red remains.


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