Have you ever seen an image that can look like two different things at once? For example, there’s a famous picture of a young woman with a feathered hat looking over her shoulder. But if you look again, her chin also looks like the nose of an older woman looking down. Another example is an image of a vase that can also look like the outline of two faces. These are called ambiguous figures because they make your brain switch between different ways of seeing the same picture.
There’s a really cool visual trick you can try at home, and it’s one of my favorites! You can make it look like there’s a hole in your hand using just a piece of paper. Here’s how you do it:
After a little while, it will seem like there’s a hole in your hand, right where the tube is. It’s a fascinating trick!
This illusion happens because each of your eyes sees a different image. Your brain usually combines these images into one, but sometimes it can’t. When that happens, your brain might ignore the image from one eye, making the other eye’s image more dominant. In this case, your brain tends to ignore your hand because it’s not as strong of an image. This is called binocular rivalry.
Binocular rivalry involves several parts of your brain, especially those involved in processing what you see. At first, neurons in your brain respond to what each eye sees. Later, some neurons might turn on or off, changing what you perceive. Scientists think that one of the images gets suppressed somewhere in this process, like there’s a gate that decides which image you become aware of first.
Normally, you don’t notice this switching between images because your eyes are always moving, looking at different things. But with binocular rivalry, your experience changes even though what you’re looking at stays the same. The input from your eyes doesn’t change; it’s your brain that does the magic.
This trick is a fun way to show how amazing your brain is. Next time you’re at the dinner table, you can impress your friends by turning your hand into something wild, like a velociraptor hand! Enjoy experimenting with this cool illusion!
Find a few examples of ambiguous figures online, like the young woman/old woman or the vase/faces image. Try to see both interpretations of each image. Discuss with your classmates which version you saw first and why you think your brain chose that interpretation.
Draw your own ambiguous figure that can be seen in two different ways. Share your drawing with the class and see if your classmates can spot both images. This will help you understand how artists create these fascinating illusions.
Try the “hole in your hand” illusion described in the article. Write a short paragraph about your experience and explain why you think this illusion works based on what you’ve learned about binocular rivalry.
Conduct a small research project on binocular rivalry. Find out more about how the brain processes conflicting images and present your findings to the class. This will deepen your understanding of how visual perception works.
Create an art gallery in your classroom featuring different optical illusions. Work in groups to design posters explaining how each illusion works. Invite other classes to visit your gallery and explain the science behind each illusion to them.
Here’s a sanitized version of the transcript:
—
This is an image of a young woman with a feathered hat looking over her shoulder. Or… is it? Her chin also resembles the nose of an older woman looking down. And take this image of a vase. Is it a vase? It’s also the outline of two faces. These perceptual illusions are called ambiguous figures because they cause you to switch between different ways of viewing an object.
There’s one type of visual phenomenon that’s particularly intriguing – it’s my favorite! To experience it, I’m going to show you how to see through a hole in your hand using just a piece of paper. It’s really simple! Start with a piece of paper or even a banknote and roll it up into a narrow tube. Hold that tube up to your eye and look through it.
Then, place your other hand against the piece of paper, about 2 inches or 5 centimeters away from your face. Keep your hand there and look into the distance through the tube, without focusing on your other hand. Give it a little time, at least 10 seconds of looking down the tube. What you can see seems like your field of vision merging, allowing you to perceive a hole in your hand, with the hole being the center of the tube you’re holding. It’s quite fascinating!
So, what’s happening here? Two different images are being shown to each of your eyes. If your brain can’t combine these two images, it suppresses the image in one eye, making the other eye more dominant. In this case, your hand generally stays suppressed from your awareness because it’s the weaker stimulus. This phenomenon is known as binocular rivalry.
Several brain areas and processes are involved in binocular rivalry, including what occurs in your visual pathway. The neurons in the early stages of visual processing respond to the physical stimulus of each eye, but then neurons in later stages can be activated or deactivated, causing alternations. Researchers believe that signals from one of the stimuli are suppressed somewhere between these stages, as if there’s a gate to visual consciousness that some signals open first.
You don’t usually notice this dominance and suppression in your eyes because they rarely stay fixed on one thing for more than a few hundred milliseconds. What makes binocular rivalry so amazing is that your perceptual experience changes while the physical stimulus remains the same. The input from your eyes is constant – the difference occurs in your brain.
Of all the ways you can trick your brain, this is a fantastic one to show people because you can turn your hand into anything at the dinner table. Velociraptor hand! See you next week.
—
This version maintains the original content while ensuring clarity and appropriateness.
Illusion – A false or misleading perception of reality, often caused by the way our brain interprets sensory information. – The optical illusion made the straight lines appear wavy, confusing our sense of sight.
Brain – The organ in our head that controls thoughts, memory, emotions, and the way we understand the world. – Scientists study the brain to learn how it processes information and controls behavior.
Images – Pictures or visual representations of objects that our eyes see and our brain interprets. – The brain processes images from our eyes to help us understand what we are looking at.
See – To perceive with the eyes; to understand or interpret visual information. – When we see a rainbow, our brain is interpreting the light that is bent by raindrops in the sky.
Visual – Related to seeing or the sense of sight. – Visual aids, like diagrams and charts, help students understand complex scientific concepts.
Rivalry – A situation in which two or more things are in competition or conflict, often used to describe how different parts of the brain might compete to process information. – In visual rivalry, the brain struggles to decide which of two conflicting images to focus on.
Neurons – Cells in the brain and nervous system that transmit information through electrical and chemical signals. – Neurons communicate with each other to help us think, feel, and move.
Perceive – To become aware of something through the senses, especially sight. – Our brain can perceive depth by comparing the images from each eye, allowing us to see in three dimensions.
Trick – Something that deceives or misleads, often used to describe how the brain can be fooled by illusions. – The magician used a clever trick to make it seem like the coin disappeared into thin air.
Fascinating – Extremely interesting or captivating, often used to describe something that captures our attention and curiosity. – The study of how the brain works is fascinating because it reveals so much about human behavior and thought.
