These lines are the same length. The angles of the arrow's head and tail that make the lines look different lengths. Scientists believe it's because the first one may remind our brains of a near side of a building which would make it look longer than the second one may reminds of a far side of a building which would be farther away .
By: Anna Wozniak
"MULLER-LYER ILLUSION." Http://www.optics4kids.org. N.p., n.d. Web. 13 Mar. 2015.
"Müller-Lyer Illusion." Http://en.wikipedia.org. N.p., n.d. Web. 13 Mar. 2015.