Activity 1: The Human Brain and Illusions

We kick off this camp by exploring sensation, perception, and the basics of the human brain. Scientists use illusions to study many parts and functions of the brain. It is important to explore the concepts of sensation and perception as we jump into how these illusions work.

Video introduction to the concept of sensation, perception, and the function of the human brain in both. There are activities sprinkled throughout.

Thank you for joining our CART Summer Camp! We hope you have fun learning about your brain and illusions.

Activity 1.1 Jumping Power Lines

Show this illusion to people in your home and ask them, “What do you hear?” If they hear anything, they should respond with an onomatopoeia (a word that sounds like its meaning such as “bang”). Record if they heard something or not.

To share and compare your findings with the rest of the class click here.

If you would like to learn more about what neuroscientists think causes this pneumonia in the brain you can read more in this article from the Smithsonian (secondary source) here or you can read the summary (abstract) from the original research paper (primary source) here.

Activity 2.1 Brain Parts and Functions Mnemonics

To become a great illusionist you should work on memorizing these basic parts and functions of the human brain, after all, you’ll be manipulating them. Draw an image of the brain, like this one here.

Label each lobe and then draw or write mnemonics to help you remember the function of each lobe.

We are sure you have used mnemonics before, but maybe you are not familiar with the word “mnemonic”. A mnemonic (pronounced nuh·maa·nik) helps you to learn and memorize new information by connecting the new idea to additional or pre-existing information. For example, to remember that “gustatory” has to do with taste I can think, “GusGus likes to eat,” which is a mnemonic; it connects what I already know about the Disney movie Cinderella with the new word gustatory. Sometimes mnemonics are sentences; such as, “How I wish I could calculate pi.” In this mnemonic, if you add the number of letters in each word you will get the first seven digits of pi (π) 4.141592. You might know this famous spelling mnemonic, “I before E except after C” (but be careful with this one, it definitely has some exemptions to the rule). Sometimes they are images such as this one that can be used to help you remember their, is used when referring to a person, while there is use for a location.

We are excited to see what kind of mnemonics you can create to learn these parts of the brain. If you would like to share what you create you can email a picture of your brain mnemonics to us at and we will try and add it to our wall of fame. Make sure only the mnemonic is in the picture and if you’d like to be recognized include your name and the school you attend.

Activity 2.2 Frontal Lobe Illusion

Illusions that confuse your “thinking” brain use primarily the frontal lobe. Here is one such illusion.

Supplies: Find some paper and something to write with and then watch the following video.

Extensions: Conduct your own experiment

  1. You can test this on your family by either playing this video or reading the words yourself. See how many people you can get to write down the word sleep. Do you notice any patterns about the people who do and don’t write down sleep?
  2. Try and create your own word list and see how successful you are at getting people to remember a word you didn’t say. How successful is this new word list compared to the one we gave you?

Want to learn more? Click here to watch a video clip from Brain Games that explains how words can influence someone’s memories.

Activity 2.3 Touch, Taste, and Smell

All of the lobes of your brain work together to create your perception of the world around you. Here is a fun experiment to try on someone in your house.

Supplies: Two types of fruit or vegetables with similar textures (we recommend using an apple and a pear, but be creative it will work on most foods, if you have baby food in the house it works really well!), a partner (anyone who lives with you will work), and a blindfold (you can always just trust each other to keep your eyes closed if you don’t have one). Have someone cut the apple and pear into the same bite-sized cubes.

Experiment: Have one person wear the blindfold and pinch their nose closed and have them try either the apple or pear. Make sure they chew with their mouth closed! Ask them to identify what they are eating, then have them let go of their nose and ask them again. Try it a few times randomly selecting either the apple or the pear.

What is happening? Turns out what you taste is very much dependent on what you smell. When you cannot smell the food you are using bottom-up processing from the information given to your parietal lobe regarding the texture and taste of the food. There is some top-down processing, thinking about what food “feels” like this, but the true top-down comes when you are allowed to breathe. Then your brain synthesizes the information in the parietal lobe about texture and taste with the information in the temporal lobe about the smell.

Extensions: Do you really want to freak your family out? Bring in the occipital lobe and the sense of vision! Make some square brownies and some “poop” brownies, try to serve the “poop” shaped brownies, and look at their facial responses. Put some chocolate pudding or green baby food in a diaper, tell them what it really is, and then try to get them to eat it! When you bring in vision it doesn’t matter how good it smells, the top-down process is dominated by your occipital lobe and most people cannot get past what it looks like in order to find out how it tastes.

Want to learn more? What role does vision play in taste? Click here to watch experiments on How Color Affect Taste, from Great Courses

Activity 2.4 Sound and Vision:

Some illusions can be created by playing on the connection between vision and sound.

Supplies: You will need a computer with Adobe Flash Player enabled in order to try this one out. If your computer doesn’t have Adobe Flash Player enabled or if you are on a tablet or smartphone you can use the second link for a video that is a similar activity.

Create the following data table:

Experiment: Click here to go to the Illustration of Binding activity and follow the instructions for trial 1. Make sure the sound is on! When you get your results, write the percentage of correct responses (the red number) in the box under Round One. After filling out the data table hit the green rewind button to try again without the beeps. Write the percentage correct in the box under Round Two.

If your device does not have Adobe Flash Player enabled, use this link to be directed to a similar activity.

What’s happening? Hearing and seeing something at the same time confuses the brain. In trying to understand the bottom-up sensory information it is receiving, it is using a top-down approach to bind the information together. Your brain has learned from experience that the number of flashes and beeps should be the same, so it makes your “perception” match this belief system, creating the illusion of more flashes than you actually saw. The frontal lobes of the brain are trying to synthesize information your temporal lobes are receiving about sound with the information in your occipital lobes are receiving about what you’re seeing.

Extension: Create a Google Slide show or a PowerPoint presentation where you control the sound and images. Is there a limit to how fast the flashes or beeps need to be? If they are far apart, is it more or less confusing?

Use the Illustration of Binding link and test different people in your house. Does age have an effect on the results? You could also take the test multiple times, do you get better? The test is always given in the same pattern, could your brain subconsciously learn the pattern and overcome the illusion?

Want to Learn More: It’s not always the ears that change what we see, what we see can also change what we hear. Click here to watch the video, Can You Trust Your Ears?, found on YouTube, it has several fun examples of auditory illusions.

2.5 Geometric Optical Illusions

Vision is the sense that we depend on the most so it makes sense that the most common illusions would be optical illusions. As a result, there are multiple categories of optical illusions. The most common that helps us to understand the role that top-down processing plays in optical illusions is the famous Panzo Illusion, or more simply the train track illusion.

Supplies: You will need a ruler. If you cannot find a ruler just grab a piece of scrap paper

Experiment: Use the ruler to measure the two yellow bars in the image below. Don’t have a ruler? Cut or fold (or rip) the piece of scrap paper until it is the size of one of the yellow rectangles in the image below and then use it to confirm that they are both the same size.

You can also watch this video if the yellow bar is moving by clicking here.

What is happening? This illusion relies on your top-down processing of the information being received by the occipital lobes. You’ve had experience with three-dimensional space your entire life. Your brain understands that the train tracks are not getting smaller but instead moving away from you towards the horizon. Your brain interprets the yellow rectangle as far back in space as the horizontal lines of the train track that it is next to. Therefore, your brain assumes the top rectangle is larger than the width of the tracks and the bottom rectangle is smaller and not as wide as the tracks. Without the lines created by the train track, the illusion fails to work.

Extensions: Will the illusion work if you did not have the horizontal lines? What if the two bars are different colors? What about the triangle created by the train track, can it be too big or too small? Write out some questions of your own and then click here to use the virtual Ponzo’s Illusion at Wolfame to test your theories.

Want to learn more? The Ponzo illusion is one type of geometric illusion. Scroll through a couple more famous ones and see if you can figure out the geometric trick that is being used to create the illusion before clicking on the link to read more about the illusions.

Which table is larger?

The two tables are identical. To prove it, measure the vertical side of the table on the left with the horizontal size of the right. Or trace the tabletop of the tables, cut it out, rotate it, and lay it on top of the other table. It will be a perfect fit! Your brain’s top-down understanding of how 2D images are in space creates the illusion that the table on the left is longer and more narrow than the table on the right.

Who has the wider smile Ope or Celo?

This is a variation on the famous Müller-Lyer Illusion. For an explanation of how the Müller-Lyer Illusion works click here. If you want to try manipulation the illusion click here.

The Hering Illusion

For an explanation of how the Hering Illusion works click here. If you want to try manipulation the illusion click here.

The Wundt Illusion

For an explanation of how the Wundt illusion works click here.

Helmholtz’s Square There are three sets of squares below. Determine which square appears the largest in each set

For answers and explanations click here. If you would like to try manipulating the illusions in sets 1 and 2 by clicking here.

Ebbinghaus or Titchener’s Illusion

For an explanation of how the Ebbinghaus or Titchener’s Illusion works click here. If you want to see how adjusting the circles affects the illusion by clicking here.

The Cafe Wall



For an explanation of how the Café Wall Illusion works click here. If you want to adjust the illusion click here.

Oscar Reutersvärd’s Triangle Illusion

Sometimes geometry can be used to create illusions called impossible images. Oscar Reutersvärd’s 1934 triangle illusions are a good example.

Each line of the triangle can move from the foreground to the background. You can learn more about Oscar Reutersvärd here.

M. C. Escher Ascending and Descending

Another famous artist who used geometry to create never-ending scenes was M. C. Escher. He created the Ascending and Descending print in 1960.

If you look closely you will notice that some soldiers will forever be going up the stairs while others will continually go downstairs. To learn more about E. C. Escher click here.

Sir James Fraser’s Spiral

This illusion by British psychologist Sir James Fraser published in 1908 looks like a spiral. Take your finger and try to trace the spiral.

Exactly how your brain creates the illusion of the spiral is not fully understood, but what do you think would happen if the circles were solid black?

What if you took the background away?

To learn more about this illusion click here.

Some geometrical illusions create the illusion of motion.

This is one such illusion created by C. H. Judd in 1899 for his study of geometrical illusions. These types of illusions are not fully understood and we discuss some theories as to how they work after we have learned more about how the eye receives visual information.

Challenge: Creating your own geometric illusion. If you would like to share your creation you can email a picture of it to
and we will try to add it to our wall of fame! Make sure the photo is only of the illusion (sorry we cannot post a picture of you with your illusion). If you’d like some recognition, include your first name and the name of the school you attend.


This module has multiple activities. Needed material and alternatives are listed within each activity. 0
Build date: 2020-07-13 16:03:10.92994922 +0000 UTC m=+0.093425000