Franz Carl Müller-Lyer was born. Renowned for devising and giving his name to the Müller-Lyer illusion, a visual distortion also known as the arrowhead illusion which leads most people to perceive that the line with the arrowheads pointing away from each other is shorter than the line with the arrowheads pointing towards each other, when in fact, the two lines are exactly the same length.

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Optical Illusions