Do your eyes ever play tricks on you? Maybe you’ve seen something that puzzled you so much that you had to rub your eyes and look again? Chances are you may have been tricked by an optical illusion.

Optical illusions are images or pictures that we perceive differently than they really are. Put another way, optical illusions occur when our eyes send information to our brains that tricks us into perceiving something that does not match reality.

The word “illusion” comes from the Latin word illudere, which means “to mock.”

Some optical illusions are physiological. This means that they’re caused by some sort of physical means in the eyes or the brain.

The Mach band illusion is an example of a physiological illusion. The line in the middle of the picture is one solid color. However, because of how the eye’s retina filters the different shades on either side of the line, the right side of the line appears darker, while the left side of the line appears lighter.

Other optical illusions are cognitive. Cognitive illusions, such as ambiguous, distorting and paradox illusions, occur when our brains automatically make assumptions based on the information sent from the eyes. These illusions are sometimes called “mind games.”

Ambiguous illusions are pictures or objects that can be seen in more than one way. Rubin’s vase is one popular example of an ambiguous illusion. Can you see both the vase and the two faces?

Distorting illusions use different techniques to make objects of similar size, length or curvature appear distorted. A famous example of a distorting illusion is the Müller-Lyer illusion.

Doesn’t the line in the middle look longer than the ones above and below it? However, all three lines are the same length!

Paradox illusions occur as a result of pictures or objects that cannot exist or are physically impossible. Paradox illusions are popular in works of art, such as those made famous by artist M. C. Escher.

His Waterfall is a classic example of a paradox illusion. Do you see how the water from the waterfall appears to travel uphill before once again reaching the top of the waterfall?

Scientists believe optical illusions are possible because our brains are so good at recognizing patterns and “seeing” familiar objects. Our brains work quickly to make a “whole” image from separate pieces.

Clever artists can use these tendencies to trick our eyes and brains into seeing what’s not really there!


34 Join the Discussion

1 Star2 Stars3 Stars4 Stars5 Stars  (35 votes, avg. 4.09 out of 5)
    • You can make stuff like that too, Lily! We think it would be so fun to make that mirror project. If you decide to give it a try, let us know! Thanks so much for hanging out in Wonderopolis today! :-)

    • Good morning, Jaden! We agree, that mirror is a really cool thing! Let us know if you build one…we’d love to hear all about it! Thanks so much for being a friend of Wonderopolis and for posting today! :-)

    • Hi there, HahaXD! We love receiving and reading the comments from our Wonder Friends, and we LOVE commenting back! It’s what friends do! Thanks for leaving us this GREAT comment today! :-)

  1. This was such an interesting wonder! I had no idea that there are so many different types of illusions including distorting and ambiguous illusions. I thought that there weren’t any different types of illusions, just regular optical illusions. I am wondering why and how artist draw and create illusions. This was a fantastic wonder!

    • We’re so happy to hear that this Wonder about optical illusions made you WONDER even more, Jack! Thank you so much for sharing this comment with us today! :-)

  2. I love watching optical illusions because after a while I start getting dizzy and feel as if everything is spinning. It’s amazing how when you draw an optical illusion you have to draw every line just so and when your finished, it’s like looking through an alternate universe. When you said that it’s your eyes that are taking fake information to your head and that’s how you see the illusion, I started to not trust my eyes. I once had a book that had one illusion after the other and pretty soon I saw everything in a new perspective! I think optical illusions are so interesting and I think this is a wonderful wonder!

    • You sure do know a LOT about optical illusions, Allison! Thanks so much for sharing your comment with us. We’re glad you chose to explore a Wonder that was so interesting to you! Optical illusions are fun and fascinating to us, too, and we LOVE looking at books filled with illusions. It’s really cool to learn how our eyes, brains and bodies work together to try and fool us, isn’t it? :-)

    • That’s what makes illusions FUN, Sarah! It’s really cool to try and figure them out, isn’t it? Thanks so much for leaving us this awesome comment today! :-)

  3. I love optical illusions, because I like to try to find out how they trick your mind. I didn’t know that there were so many optical illusions, like ambiguous, distorted, and paradox illusions. I loved learning about illusions, and I’m going to find out more! :)

    • Thanks for leaving us this super comment, Jenna! We really like trying to figure out optical illusions, too…it’s a FUN thing to do! :-)

  4. I never knew that there was so many optical illusions! When I look at them, they are kind of freaky! Especially the illusions with two different objects. I kind of get dizzy when looking at the spinning ones. Optical illusions are awesome! Oh! I also thought the video was cool, too!

    • Some optical illusions make us dizzy, too, Hayden! We still think they are SUPER fun to try and figure out, though! Thanks for hanging out in Wonderopolis today! :-)

    • Thanks for sharing that you liked the video for this Wonder, Amoolya! We really like the word “FUN-TASTIC,” too! It ROCKS (and so do you!)! :-)

    • Hi there, Daesha! We really appreciate your comment! Thanks for letting us know you enjoyed learning about optical illusions in Wonderopolis today! :-)

    • We’re glad you liked this Wonder of the Day®, The Picador! We think optical illusions are super cool, too! Did you explore all the links (the colored text) inside this Wonder? There are LOTS of other links found on the web pages that those links lead to. That adds up to LOTS of optical illusion FUN! :-)

  5. Wow the video was soooooo cool. At first I had no idea what was happening but at the end my brother and I said whoa!!!!!! At the same time.

    • Hi there, Skylar! We’re so excited to hear that you and your brother have been enjoying our Wonder about optical illusions! We Wonder if you and your brother learned anything new from this Wonder? It’s pretty cool! Thanks for sharing your comment and WONDERing with us, Skylar! :-)

    • We’re so excited you learned something new with us, Wonder Friend Nicole! :) Optical illusions sure can be tricky from time to time, and we are glad you’ve been WONDERing all about them today! Nice work– we hope to see you soon! :)

    • We LOVE your enthusiasm for optical illusions, Bella! Thanks for sharing your comment with us today! :)

    • Thanks for visiting our Wonder about optical illusions, Loredana! We’re glad you thought the video was AMAZING! We’re sorry to hear the Wonder didn’t include enough information for your research! We hope you will WONDER with us again soon! :)

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>


  • Wonderopolis on Facebook
  • Wonderopolis on Pinterest
  • Print

Have you ever wondered…

  • What is an optical illusion?
  • How are physiological and cognitive illusions different?
  • Have artists ever used optical illusions?

Wonder Gallery

kids observing optical illusion_shutterstock_15203233Vimeo Video

Try It Out

Ready to put your eyes to the test? Check out these fun optical illusions with your friends and family:


Still Wondering

Check out Science NetLinks’ Magnify It! lesson to learn more about the limits of what the eye can see and how a magnifying glass can extend those limits.


Wonder What’s Next?

Tomorrow’s Wonder of the Day is red and juicy. If you’re curious, make sure you ketchup with us tomorrow!

Upload a Photo or Paste the URL of a YouTube or SchoolTube Video.