At first, a viral waiting room video looks completely normal. But if you watch closely visual optical illusions, you’ll notice the rug disappears, the pillows change, and even ceiling panels vanish. This clever trick is called ‘The Changing Room Illusion‘ and it won second place in the 2021 Best Illusion of the Year Contest. The contest, run by the Neural Correlate Society, shows how our brains can miss big changes – especially when they happen slowly. As The New York Times reports, the contest is co-run by neuroscientists Stephen Macknik and Susana Martinez-Conde, who have spent years studying how the brain creates its own version of the world.

They say illusions give scientists a rare window into how the mind makes sense of what we see.

You don’t see with your eyes-you see with your brain

The idea behind these illusions is simple: perception and reality don’t always match. According to Macknik and Martinez-Conde, our brains aren’t passive observers. Instead, they build an internal model of what we believe is happening-and fill in gaps when needed. “We are always constructing a simulation of reality,” Martinez‑Conde explained to The New York Times. To her, illusions highlight that perception depends on this internal model.

A contest where scientists and illusionists collide

When Macknik and Martinez-Conde launched the illusion contest in 2005, they thought entries would eventually run dry. But the opposite happened. “People kept innovating, even beyond our expectations,” says Martinez‑Conde.

Some illusions come from real life-like Aristotle’s ‘waterfall illusion,’ where staring at flowing water made still rocks appear to move. Others, like 2017’s Café Wall illusion or 2012’s Floating Star illusion, use color and shape patterns to trick the brain into seeing motion or slants that aren’t there.

Even neuroscientists can predict how illusions work. Back in 1998, Macknik guessed that a visual bar would disappear if two nearby bars were placed close enough. And he was right. When the brain tries to process too many similar signals at once, some simply get cancelled out.

Why your senses fool you-every single day

Though most entries are visual, illusions can affect all five senses. That smell that seems strong at first but fades quickly? That’s your nose adapting-another form of sensory illusion. These quirks happen because the brain is always looking for shortcuts. It wants speed and efficiency, not perfect accuracy.

That’s why so much of what we think we’re seeing is really a fast mental guess. Macknik and Martinez-Conde point out that this process, though useful, creates flaws in how we experience the world.

For scientists, illusions are more than entertainment. They’re tools that help unpack the complexity of the human mind. And for the rest of us, they’re a reminder that even when we’re sure of what we see-our brains might be playing tricks on us.

What is the meaning of the optical illusion?

An optical illusion is a visual trick that shows how our brain can misinterpret what we see.

What is the trippiest visual optical illusions?

Illusions that make static images appear to move, like the waterfall illusion, are often called the trippiest.

Why do optical illusions trick you?

They fool your brain by taking advantage of how it fills in gaps and makes quick assumptions about what you see.