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Think Vision Is All About Your Eyes? Think Again

They say that seeing is believing. But you may be surprised to discover that what you see is not always what you get. In fact, sometimes what you see isn’t even there at all.

That’s because vision isn’t always about what’s in front of your eyes – sometimes it’s about what happens in your brain. Here’s a look at how your brain’s complex relationship with your eyes defines just how you see the world.

How Your Eyes Work
Your eye focuses light onto your retina. That light is then absorbed by cells, converting the light into electrochemical signals which are sent to your brain through the optic nerve.

That much you probably knew. But those signals aren’t just sent to one part of the brain. They are actually filtered through several different areas of your brain, each of which has a specific role in piecing together the puzzle of what you are seeing.

A Picture Is Worth Ten Million Photoreceptors
After beaming down the optic nerve, most of the signals from your eyes are filtered through the thalamus, which organizes the informationinto two streams: One for color and structure, the other for contrast and motion. These streams are then sent to the visual cortex, which maps out the information vertically and horizontally while also adding depth by comparing the signals from both eyes.

So far, so good. But that’s when things start to get a bit funky.

A World of Illusion
Your primary visual cortex isn’t the only part of your brain being hit up by signals. The secondary visual cortex – the backup band for your eyeballs – also works to figure out color. Strangely enough, it does this in part by guessing, in a process called color constancy. Because colors appear differently depending on the quality of light, when it gets too dark or too bright to really make out the color, your brain simply fills in the gaps based on what you expect the color to be!

Also check out: Optical Illusions – A Battle Between the Eyes and the Brain

The same sort of thing also happens when you quickly scan your field of vision. Look around you. Everything is still there, right? Well, it might be, but your brain is just guessing. Rather than scanning smoothly, your eyes actually jump as they move, essentially taking a series of quick snapshots. Your mind then fills in the blanks, similar to the persistence of vision that made old films appear to be continuous even at just 24 frames per second.

Unconscious Inference and Gestalt Theory
How exactly the brain fills in those blanks, though, is still being studied by scientists. The Gestalt theory focuses on how the mind uses pattern recognition to extrapolate missing visual elements, while the theory of unconscious inference studies how our brains make up for deficiencies in our eyes by extrapolating from past experience.

So the next time you think your eyes may be playing tricks on you, chances are you’re actually right.