Mice and Mind Tricks: Optical Illusions

Written by: Sitara Nair

Have you ever stared at a picture and thought it was moving, even though it was just printed on paper?! Well, that’s because optical illusions are playing tricks on you! An optical illusion is a visual phenomenon where the perception of an image looks different from reality! In simpler words, what you see becomes interpreted by our brains in ways that don’t actually match the physical properties of the actual image! Optical illusions trick brains into seeing motion, shapes, colors, or depth that aren’t truly there! Well, there’s a specific reason we are talking about this today; a new 2025 study proves that illusions don’t just fool humans, they can even trick our brains’ cells one by one! Let’s learn about this study!

Background

Your eyes and brain are a team that works together to help you see and interpret the world. However, they can get tricked or confused, especially by deliberate tricks like optical illusions. When you look at one, your eyes might see something in a strange or unfamiliar way, like something that looksl ike it’s moving when its not, or a picture that looks like two different things at once! This is because your eyes will send messages to your brain, but the messages can be confusing or incomplete, so your brain tries to fill in the blanks or guess what is there, and it can often get it wrong. That’s when you see something that’s not really happening, and you get sucked into the illusion, like a magic trick!!

There are several types of optical illusions, including:

1. Literal illusions: This is where the image you see is different from the actual objects that make up said image. For example, a picture that looks like one thing from far away, but another up close. 

2. Physiological illusions: This is caused by excessive stimulation of the eyes or brain, like afterimages (those “ghost” images you see) when you look into bright lights.

3. Cognitive illusions: This is where your brain makes unconscious inferences, like images that are literally impossible or ambiguous. These illusions rely on the brain’s tendency to fill in missing information on its own (make assumptions) and lead to confusing interpretations.

Recent Discovery: Scientists Make Mice See Illusions

Scientists recently used lasers to activate special brain cells in mice, and the mice seemed to see shapes and patterns that weren’t actually there! Researchers at the Allen Institute in Seattle and the University of California, Berkeley discovered a special type of neuron called an “IC-encoder” neuron. These neurons are part of the brain’s visual system, and they can trigger the same brain activity whether there is an illusion or not. Basically, the scientists first showed mice illusion pictures, like classic shapes arranged so you think you see a triangle or square forming but its actually just circles. They were able to find that the mice’s brains lit up in certain patterns, and then they used lasers to turn on those IC encoder neurons without showing ANY pictures at all. And then, they found that the same brain pattern appeared!! That means the brain cells pretended to see the illusion even though the eyes didn’t! This shows that vision isn’t just like a camera taking a picture, but instead the brain actively builds what we see! Isn’t that so cool?! Additionally, this study is able to help scientists understand how some health problems may happen, like when someone sees things that are not really there (hallucinations). By knowing which neurons help complete patterns, researchers may find new ways to study diseases where perception goes wrong.

In conclusion, our brains are so cool and can easily be tricked by visual cues! You can even try some of these cool tricks on yourself, at home! For instance, you can create a classic illusion at home with just a piece of paper, a ruler, and a pencil. Draw two straight lines of identical lengths. On one line, add arrow tips that point outward (like:  >------<) and on the other, add inward-pointing arrows (like: <------>). Despite both lines being the same length, the line with the inward arrows will probably appear longer. This happens because your brain uses the direction of the arrows as clues and gets tricked into seeing the line differently. Optical illusions like this show how easily we can be fooled!