How Optical Illusions Trick Your Brain

Things are not at all as they seem... What are the different types of optical illusions and why are our eyes tricking us?

Think of it this way: Optical illusions represent the lighter side of brain malfunction. They're more fun than grand mal seizures, anyway. But how do they work, exactly? Jules Suzdaltsev settles his penetrating gaze on the topic in today's DNews special report.

It's helpful to start with visual perception itself, and this gets a little metaphysical, so hang in there: What we perceive as real is not really real, and we don't actually see what we think we see. Instead, our optical nerves are processing reflected light waves that are flipped upside down and reversed around the vertical access, then converted into electrical impulses which are reinterpreted by the visual cortex. It gets complicated.

But the biological upshot is that this whole visual apprehension process takes about one-tenth of a second. That's actually problematically slow, in terms of survival of the species. And so, over millions of years of evolution, the brain has developed ways to compensate for that tenth-of-a-second gap -- by basically hacking your eye-to-brain connection.

Many optical illusions work by leveraging aspects of this phenomenon. Current theories essentially break down optical illusions into three types: literal, physiological and cognitive. Literal illusions reply on the concept of pattern recognition, in which your brain tries to makes sense of incoming imagery before it actually processes the visual data.

RELATED: These 5 Optical Illusions Will Drive You Crazy!

Your brain will literally fill in details (or remove them) as it makes an educated guess at what you're looking at. The phenomenon of pareidolia -- seeing shapes in the clouds, for example -- is a kind of literal illusion.

Physiological illusions involve the workings of light-processing neurons in your eyes. Certain patterns can trick the eye by essentially fatiguing specific photoreceptors and producing a kind of focused but temporary blindness. With physiological illusions -- so far as your brain is concerned -- things can actually disappear. Like the San Francisco Giants lead in the NL West pennant race, for instance.

Cognitive illusions are the most fun, and these take place entirely within the higher-reasoning portions of your brain. They play upon inconsistencies between what you're seeing and what you're otherwise used to seeing, based on your experiential knowledge of the world.

You'll really want to check out Jules' video for this one -- he's got a sequence of optical illusion examples and visual aids to help explain all this.

-- Glenn McDonald

Learn More:

BBC: How Your Eyes Trick Your Mind

Study: What Are Optical Illusions? - Definition & Types

Inside Science: How Do Optical Illusions Work?