- Ebbinghaus illusion: Which orange circle is bigger? Guess, then hide the outer circles.
- Müller-Lyer illusion: Measure the lines with a ruler on the screen.
- Jastrow illusion: Swap the shapes and watch the "bigger" one change.
- Kanizsa triangle: Find the triangle that is not there.
- Negative afterimage: Stare for 25 seconds and see the colors flip.
- Motion aftereffect (waterfall illusion): Watch the spiral, then look at your hand.
- Rubin vase: Vase or faces? Ask a friend which they saw first.
- Necker cube: Try to flip the cube on purpose.
- Stepping feet: Do the bars walk or glide?
- Vertical-horizontal illusion: Make the lines look equal, then check your score.
Science fair idea
Use the vertical-horizontal illusion: ask 10 people to set the lines to look equal, write down the percentage each one chose and compare children and adults, or right-handed and left-handed people. Present the average and the range.
Safety
Motion illusions can make some people feel a little dizzy; just look away. Anyone with photosensitive epilepsy should avoid flickering patterns.
