Eli5: the lens of your eye flips the image of what is happening in front of you and displays it on your retina, then your brain “flips” it again for you to perceive. What is the brain doing for that second flip?

Question

Eli5: the lens of your eye flips the image of what is happening in front of you and displays it on your retina, then your brain “flips” it again for you to perceive. What is the brain doing for that second flip?

In: 23

Answer 1

So here’s the really fun part:

We tend to think of our eyes sort of like windows that we use to look out at the world. The reality is light is falling on special cells in the back of your eye that create tiny electrical impulses when they’re exposed to light. Those impulses then travel along your optic nerve to your brain which interprets those signals and presents them to you as an image.

Or to put it another way… see the screen you’re reading this on now? No you don’t. What you’re experiencing is a mental ‘simulation’ of that screen, wholly made up by your brain based on a stream of electrical pulses.

This is how optical illusions work, why our eyes are so easily ‘tricked’ because you’re not seeing through a window into reality, you’re seeing a simulation created by your brain that it editing that image on the fly to give you what it *believes* is there, emphasising important stuff while filtering out what doesn’t need your attention.

For example, both your eyes have a blind spot where your optic nerve meets your retina… but your brain just edits it out. Every time your eyes move, for the split second they’re moving, your brain cuts off the signal and you go blind to prevent motion sickness. Why don’t you notice? Because your brain is just editing your perception on the fly.

Here’s the really mind-blowing part about this: Do you know when you look at a clock and the second hand seems to stay still for a fraction of a second too long, then goes back to it’s normal movement when you keep looking at it? That’s because you went blind for a split second while your eyes moved to it… and then your brain took the image of that clock and edited it into your memory of that split second you were blind so you didn’t notice.

A lot of optical illusions work because your brain is *expecting* to see one thing and is presenting that to you because it can’t properly make sense of what is actually there.

So, with all that going on, flipping an image is not exactly a big ask for your brain to do.