Illusions are evidence of the (current) innate limitations of us humans in the perception of reality. At the same time illusions give an indication of the gathered skills people have in perceiving reality – some people are more easily fooled than others. The Müller-Lyer illusion provides an elegant example of a distorting illusion. It’s the first depicted illusion (three lines with different configurations of arrowhead(s)/arrow tail(s): an “angles in” (arrowhead) and “angles out” (arrow tail) configuration (and a third mixed configuration)) in the illustration above. The lines don’t look equally long but actually are (as indicated in the 2nd image) equally sized.