Can You Spot What's Unusual About the Cars in This Optical Illusion?

If you think the cars in this image are different sizes, take a closer look.
If you think the cars in this image are different sizes, take a closer look. / Big Motoring World

Even if you have perfect vision, you can’t always trust what your eyes perceive—take this mind-bending optical illusion from Big Motoring World as an example. Most people who see it will say that the cars “closer” to the viewer are smaller than the ones farther back in the scene. If that’s your first impression, take a closer look: Measuring the vehicles reveals that they’re all the same size.

If your eyes were tricked by the image, that means they’re working just fine. Objects appear bigger or smaller in your field of vision depending on how near or far they are, so your visual system uses context clues to determine their true size. This mechanism can be hacked to produce something called the Ponzo Illusion. Italian psychologist Mario Ponzo first illustrated it in 1911 using two lines laid over a sketch of train tracks. 

Ponzo Illusion
Ponzo Illusion / Wikimedia Commons

The horizontal lines are both the same size, but the human brain assumes the one at the bottom where the tracks are widest is closer, while the one further up where the tracks are narrow is in the distance. The brain adjusts the sizes of the objects to account for their perceived distances. In reality, the lines are part of the same two-dimensional image, and any difference in size or distance is an illusion. 

The picture at the top of the article employs this same effect. Instead of train tracks, it uses a road that appears to narrow as it extends toward the city skyline in the distance. This makes the two cars closer to the horizon look larger, when in reality they’re all the same size. If you don’t believe your eyes are lying to you, holding your fingers up to the cars on the screen should quickly dispel the illusion. 

Not every tricky image can be beat so easily. Here are some award-winning optical illusions to give your brain a workout.