Can you trust what you see? Take a look at these two cards. Which card appears larger?
Courtesy of BrainFacts/SfN
Now, watch the animation. What do you see when the cards move on top of each other?
Why does this happen? Your brain is always making comparisons. Here, your brain compares the edges that are closest to each other. Due to the curvature of the cards, the inside curve of the card on the left is longer than the inside curve of the card on the right, making the left card appear bigger when in fact, the cards are the exact same size.