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“What’s up, doc?” Most of us instantly recognize Bugs Bunny, but here’s something wild—Bugs himself is an optical illusion. Cartoons, at their core, are a clever trick played on our eyes and brains. They’re made up of individual images, each slightly different from the last. When shown in rapid succession, our brains don’t see separate pictures—they see smooth, continuous movement. It’s the same principle behind a flipbook: flip the pages fast enough, and a simple drawing seems to come to life.
Animation works by taking advantage of how our brains process visual information, filling in the gaps between still images to create motion. But this trick isn’t just used in cartoons—optical illusions influence everything from art to science to technology. By understanding how illusions work, we can uncover the secrets behind not just animation, but how we see the world around us.
How Optical Illusions Work
Our brains are wired to make sense of the world as quickly as possible, but sometimes, they take shortcuts that don’t quite match reality. Optical illusions happen when our brains interpret visual information in unexpected ways, tricking us into seeing something that isn’t really there.
Take the Müller-Lyer illusion—two lines of the same length appear different just because of the arrow-like shapes at their ends. Your brain automatically adjusts for perspective, even when there’s none. These illusions aren’t just fun puzzles; they reveal how our brains use context, contrast, and assumptions to interpret the world. Understanding them gives us a glimpse into the powerful—and sometimes flawed—ways we process visual information every day.
Exploration
When I introduce optical illusions, I let students dive in and explore on their own. These kid-friendly websites are a great place to start. Most students get so curious that they don’t need a structured assignment to stay engaged, but it helps to give them a way to share their discoveries. One option is to have students submit their favorite illusion on a simple form, explaining what makes it interesting. Another is to hold a class discussion where students compare illusions, describe what they see, and debate why their brains might interpret them differently. This not only gets them thinking critically but also sparks excitement about the science behind what they see.
Optics 4 Kids Optical Illusions: This is a collection of fun, interactive illusions that demonstrate how our brains can be tricked by patterns, colors, and shapes. The site provides clear explanations of each illusion, helping kids understand the science behind what they see.
Optical Illusions for Kids: Showcases a variety of kid-friendly illusions with simple explanations of how they work. The site encourages curiosity by breaking down the science behind visual tricks in an engaging and accessible way.
Visual Phenomena and Optical Illusions: This website features an extensive collection of interactive optical illusions, each with explanations of the science behind them. The site is designed for curious learners of all ages, offering a deep dive into how our brains interpret (and sometimes misinterpret) visual information.
Illusions: This page offers a fun collection of classic illusions that challenge how we see and interpret images. Each illusion comes with a simple explanation, making it an engaging way for kids to explore the science behind visual perception.
For a deeper dive into how optical illusions work, you can show the two videos below. I’ve used them with middle school students, and most are able to follow along, but it’s a good idea to pause and review key points to ensure understanding, especially with younger students. Discussion questions for both videos are included in the lesson slideshow.
Nathan S. Jacobs' TED-Ed video, "How optical illusions trick your brain," provides a clear and engaging explanation of how these visual tricks work. Jacobs breaks down how our brains process visual information and why we sometimes misinterpret what we see, using concrete examples to make complex ideas easy to understand.
Mark Changizi's TED-Ed video, "Why do we see illusions?", explores the evolutionary origins of optical illusions. He suggests that illusions may result from our brain’s ability to predict future events, offering a unique perspective on why our brains sometimes misinterpret what we see.
Activities
Hands-on projects are a great way to understand how optical illusions work because they turn abstract ideas into real, interactive experiences. While reading or watching videos can help students grasp the theory, creating and manipulating illusions allows them to see the principles in action.
By creating optical illusions, students not only see how lines and colors trick the eye, but they also engage in a process that makes learning more effective. It's like learning to ride a bike—doing it helps you understand it better than just reading about it. Creating illusions challenges students to think critically and solve problems, which strengthens their skills. Plus, using their hands and eyes makes the process more fun and memorable, sparking further curiosity and interest in learning. Here are 3 hands-on activities I've done with students that are easy to complete and provide a great opportunity to explore the concepts behind optical illusions.
This video tutorial shows how to create a 3D optical illusion of your hand on paper. By tracing your hand, drawing straight and curved lines, and adding markers, you'll bring the illusion to life with a realistic 3D effect.
This site gives step by step instructions for drawing 3D stairs. This is a technique used to create sidewalk drawings that trick the eye into seeing realistic, three-dimensional scenes, like a pool in the street.
The Penrose triangle looks like a normal three-sided shape, but
its angles twist in a way that makes it impossible in real life. This video simplifies the construction of the Penrose Triangle, a classic impossible object popularized in 1958.
Materials
Paper
Pencils
Colored pencils
Markers
rulers
Resources