This super simple optical illusion lets you turn two pictures into one! Did you know your brain uses shortcuts in order to process all the millions of things we see at any one time? An optical illusion “tricks” your eyes and brain.
When you spin the pencil, your brain sees one image first and then the second image before it finishes processing the first, so you see two images at the same time.
This effect is called persistence of vision.
What you need:
- White cardboard
- Pencils or colouring pens
- Straw or pencil
- Scissors
- Glue/tape
How to make an optical illusion
- Cut out two squares from a sheet of white cardboard.
- You can draw anything, but part of the picture must be on one square of the card and the other on the second piece of card. It can be a bit tricky to get the positioning right, so keep it simple.
- Glue or sellotape a pencil in between the two pictures.
- Hold the pencil between your palms and rub your hands to make the picture spin around.
This activity is also part of my Tray a Day science series, which is full of science activities you can fit in a tray!
Grab the experiment instructions from the image below!
If you liked this, you might like my other science experiments using paper or super simple science tricks!
Last Updated on February 13, 2025 by Emma Vanstone
Oh fantastic, simple but know William will loveit!
This is an old favourite. When the flicker rate is high enough, the brain starts to blend the two images so we see the bird in the cage. Wonderful. How sad it would be if this were not so. Seeing a movie would become a series of still images.
Ross Mannell (teacher)
Australia
Hi saw you on linky party, what a great project for the kids! Now google following, would love it if you popped by, Karima 🙂 http://www.karimascrafts.com
Interesting. Thank you so much for linking up to Upcycled Awesome at http://www.thetshirtdiaries.com
Kids love this one! Thanks for sharing. Saw you at For the Kids Fridays.
Totally doing this one! I want to do this myself. Thank you for sharing.
So glad you liked it! x
Great fun! Love it when science and play go together.
Thank you. x
You have such fascinating ideas! Thank you for sharing this on The Sunday Showcase!
thanks for bringing back memories of childhood science projects! my boys will LOVE this one, and I’m quite sure will run to school with it! thanks so much for sharing on Craft Schooling Sunday!
Thanks for sharing this with the Play Academy – great to see the video showing how it really works.
What a simple yet fun activity for kids. We’ll definitely be having a go. Thanks so much for sharing it. Pinned! 🙂
Great experiment to explain optical illusions! Thanks for sharing it with Afterschool!
I remember how fun these were to make as a kid. Thanks so much for sharing at After School!
That is so cool! God has made our brains with such skill and design!
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