Pointing Arrows

The Mueller-Lyer Illusion: The two horizontal lines are of the same length, even though the one at the bottom seems longer. As you know, the visual angle gets smaller with distance, so the brain automatically perceives objects at farther distances to be bigger. In general, lines that have inward flaps, such as corner of a building, are relatively the nearest points of the overall object. Similarly, lines with outward flaps are found at the longer distance, as the farthest corner of a room. So in the Mueller-Lyer illusion, the brain perceives the line with outward flaps to be at a farther point as compared to the line with inward flaps. Consequently, the brain perceives the line with outward flaps to be longer.