Have you ever had the eerie feeling that your eyes might be playing tricks on you? Chances are you’ve seen many optical illusions that look like one thing – until they don’t. Or perhaps it’s a still image that looks like – is it? – it’s definitely moving. Right? . . . Interestingly, the term optical illusion itself is a bit of a misnomer. That is, optical illusions aren’t necessarily puzzles that trick our eyes – they actually deceive our brains.
Our entire visual system has many different parts – including our eyes. This complex system also includes the optic chiasm, the optic nerve, and the visual cortex of our brains. These parts work together when light enters our eyes and focus onto our retinas. These retinal cells turn that light into electrical signals that are sent via the optic nerve to our brains. This visual system allows our brains to interpret data by forming an image in our minds – so we “see” not with our eyes, but with our brains.
Amazingly, this entire process takes just one-tenth of a second!
We’re able to see, relay, and process these images quickly because of the tools our eyes and brains use to compile images. By taking note of things like defined borders and contrast, our visual systems often take shortcuts, guessing what should be part of an image based on our previous experiences. Usually, these shortcuts do their jobs so well we don’t notice them at work. But sometimes – like when an optical illusion is at work – we find ourselves fooled.
Because our eyes receive a constant stream of light, they’re also receiving a huge amount of information at all times – trying to focus on everything all at once would be akin to trying to drink water from a firehose. These shortcuts were necessary to early humans for survival and have held on to help us navigate today’s world.
Different illusions use different types of shortcuts to work: they may play with patterns, light, and color (or the absence of color) to create images that deceive our visual system. Some optical illusions can trick our brain into seeing motion where there is none. Others mislead our brains into perceiving a shade that isn’t actually visible.
Funnily enough, our brains can be trained, in a way, to recognize optical illusions. Many illusions have been around for a long time or are variations on old classics. If your brain has seen an illusion before, or one that was similar, it’s almost impossible to un-see the “trick” to the illusion, because our brain accesses that previously-learned knowledge and joins it with current visual cues – boosting our failed shortcuts.
While research has explained why some of these illusions fool our brains, not all tricks have been explained by science. One thing we do know: our visual system is too limited to take in and evaluate all of the information taken in by our eyes, making the old cliche a falsehood: seeing is not always believing.