Why you see identical lines as differentThe visual trick caused by living inside boxes.

From the show

Brain Perception Illusions

This famous optical illusion reveals that your perception isn't a perfect reflection of reality, but a guess your brain makes based on past experience. It shows how two identical lines can appear unequal in length due to fins at their ends. The leading theory suggests our brains misapply 3D depth cues learned from a lifetime of seeing corners in our built environment. This simple error demonstrates how our 'carpentered world' fundamentally shapes what we see.