# Seeing Is (Not Always) Believing!

Visual illusions and other optical puzzles are fun for families to share and explore. With hands-on science projects and activities, students can create and test their own visual illusions. For more advanced exploration, a new electronics science project guides students in creating a mesmerizing infinity mirror that invites viewers to gaze into a seemingly infinite tunnel lit by a series of lights.

Image: Wikipedia.

How many triangles appear in the image above? The correct answer is zero, but your brain probably perceives several triangles because your brain is filling in information that is not actually present. Your brain is "interpreting" the image as a whole, despite what your eyes are actually "seeing." You probably see a white triangle atop of what you assume is a black outlined triangle. You may also argue there are other clear smaller triangles within the image as well! But this image, known as a Kanizsa Triangle, contains no triangles at all.

The Kanizsa Triangle is comprised of three "v" shapes and three "Pacman"-style, open-mouth shapes. The white triangle seemingly formed by the negative space is something our brain interprets even though it isn't drawn into the image. In fact, the "white" of that central triangle flows unimpeded into the white of the background. There is no defined triangle—other than the one our brain perceives.

The visual illusion created by the Kanizsa Triangle is one of a number of types of perceptual illusions, and, like sleights of hand that a magician might perform, visual or optical illusions are fun because they trick the eye and challenge us to understand how our eyes and brain work together.

How many dark dots appear in the following image?

Image: Wikipedia.

Did you have trouble isolating or counting the dark dots? The above image is a grid illusion, specifically a Hermann grid illusion. You will find similar versions with more boxes and more dots, but the problem of counting the dark dots remains because as your eye moves around the image, the dark dots seem to shift. In fact, there are no dark dots at all in this type of grid illusion, just white lines on a black field.

Visual illusions are engaging puzzles because they tease the brain. The brain and the eye don't agree about what they are seeing or how to interpret the information. Do you see an old woman or a young one? Do you see a rabbit or a duck? Do you see two vases or a face? In some types of visual illusion, you may see more than one image, your brain bouncing back and forth between possible interpretations as your focus shifts.

There are countless visual illusions to explore, and delving into the "why" we see (or think we see) what we see is a great way to learn more about the eye, the brain, and human biology and neurology.

Making Connections

Students and families can explore visual illusions with the Afterimages: The Colorful Tricks Eyes Play science activity. The activity, a simplified version of a longer, independent science project, helps students explore what happens when you stare at blocks of color for a long time, effectively fatiguing color-receptive cones in the eye. Better than a game of who can not blink for the longest amount of time, this fun science exploration challenges you to stare at something for a set amount of time.

An Endless Tunnel?

How many LEDs do you think are used in the construction of the infinity mirror shown above? How deep do you think the infinity mirror is? You might be surprised! Get answers to these questions by making your own infinity mirror in the Explore Optical Illusions science project.

If you can do it without blinking, you may see something that isn't really there!

To explore other ways to experiment with afterimages, including combining fun computer programming tools and environments, like Scratch, see A Trick of the Eye for Halloween. A classroom-friendly exploration of afterimages is also available, complete with educator and student materials.

Electronics Fun with Illusions

While many familiar visual illusions are flat renderings designed to be viewed on paper (or on a screen), with a bit of creativity and electronics know-how, you can create cool dimensional optical illusions that will further challenge viewers to understand what they are really seeing. In a mirror at a carnival, for instance, you may appear either shorter or taller, or thinner or wider, than you really are. Or, you might wander through a fun house room of mirrors, looking for a way out.

A new electronics engineering project at Science Buddies guides students in creating an infinity mirror. In the Explore Optical Illusions: Build an Infinity Mirror project, students design and construct an infinity mirror from a cardboard box, a set of LEDs, and two mirrors. When activated, a viewer looking into the mirror will see what appears to be an infinitely long tunnel, a lit tunnel stretching far into the distance of the box. But the box is really just a shallow box!

Creating your own LED infinity mirror is a fun DIY electronics project. In the end, you will have a light-up optical illusion that will amaze friends and family!

Award-winning Optical Illusions

For more fun with visual illusions, check out the Dynamic Ebbinghaus visual illusion, the winning entry in this year's Best Illusion of the Year Contest. You can view all 10 finalists from this year's contest on the contest site. It is fun to look at the visual illusions and to read the descriptions that accompany each. Some of these are real eye puzzles!