This illusion shows our inability to accurately compare shapes. The two cards are exactly the same size and shape yet the card on the left looks bigger.Drag the right-hand card over the other card. See that they are the same size.Now drag the card to the opposite side. It now looks bigger and even appears to grow as it moves! This illusion works because we like to compare contours when we judge size. We assume the shorter curve of one card will make it smaller in comparison to the long curve of the other card.