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How Can a Monster Look Bigger Than It Really Is? – Optical Illusion for Kids

This science project for kids is super simple and easy, but the results are really neat. When you move the monster, it appears to shrink or grow depending on its surroundings. This would be great in a project on optical illusions!

Grace says this project is more art and less science, but there is good science behind it, and it is fun. So that’s that, and I included it.

The idea is that you create a three-dimensional city on a flat piece of paper, and then you can place a cut out monster in your city in various places to see him appear to shrink and grow depending. My kids had fun with it.

The biggest part of this project involves drawing your city scape. This has to be done precisely so that all the lines converge at the vanishing point, which I’ll explain below.

Even though this has to be done carefully, there’s no reason why kids can’t do it. I was short on time and did ours myself, but I think Grace could have drawn it herself given a little instruction.


  • Paper
  • Ruler
  • Pencil
  • Colored pencils or fine point markers


  1. Draw a dot in the center of your paper, about 1/3 down from the top. This is your vanishing point, and it is what allows your drawing to look 3D.
  2. Use a ruler to draw very straight lines from the dot to each of the corners. These represent the bottoms and tops of all the buildings.
  3. Again using the ruler, draw vertical lines in between the lines on the left and right sides of the paper. These lines will be the buildings themselves. The buildings near the vanishing point should be very small (narrow), and the buildings at the edges should be very wide. See below.
  4. Using the ruler, draw in doors and windows on the buildings. The tops and bottoms of the doors and windows should line up perfectly with the vanishing point in order for the illusion to work correctly. Also, you need to make the doors and windows very small near the vanishing point and much larger near the edges of the paper.
    Notice in my sample below how the doors and windows don’t necessarily line up with each other (stagger them for more interest in the drawing), but they are all parallel to the line at the bottom of the buildings. This is super important.
  5. Finish the buildings by drawing roofs. I lack artistic talent, and my roofs are very, very lousy. This doesn’t matter.
  6. Draw in some stick figure people. The ones near the vanishing point should be very small, and the ones in the front should be bigger than the monster.
  7. Draw a monster. This activity is taken out of the Usborne Big Book of Science Things to Make and Do (no longer in print, but there is a very similar one called 50 Science Things to Make and Do – I don’t have the newer one and don’t know if this activity is in it or not.), and we used the monster sticker that came with the book. You could very easily draw your own.
  8. This is the fun part. Move the monster around on the page and see how he appears to shrink and grow. Allie explains it below:

The Science

This project works because the perspective tricks your brain. When the monster is surrounded by tiny buildings and tiny people, he appears to be humongous. When he is next to big people and big buildings, he looks small.

Extend the Experiment

You can see all different kinds of optical illusions online, including these perspective illusions. (NOTE: I have not explored much of this site, so I can’t vouch for its appropriateness for children. What I saw was okay, but I don’t know what might be buried within. Probably best to look at it with your kids.)

This project is related to the Ponzo Illusion and the Ebbinghaus Illusion, both of which you can read about on Wikipedia and other places. These illusions have been studied by neuroscience researchers who think there is a relationship between the ability to “fall for” these illusions and the size of a viewer’s visual cortex (the part of the brain that controls sight).

While optical illusions are really fun and interesting to look at, I think it’s really cool that scientists are actually studying them to learn more about our human brains. You’ll never look at illusions the same way again!

Check out Super Science Summer, my at-home science summer camp going on for 11 weeks in 2016!

© 2016 – 2018, Tara Ziegmont. All rights reserved.

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