WOLFRAM|DEMONSTRATIONS PROJECT

Ponzo's Illusion

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triangle line
change triangle angle
triangle thickness
top line
move top line
top line thickness
bottom line
move bottom line
bottom line thickness

Psychologist Mario Ponzo proposed that people determine the size of an object by taking into account the object's background. This is a Demonstration of Ponzo's illusion in which the top line is perceived to be longer than the bottom line, as a result of their relative placement in the triangle. Observe whether a change in thickness, color, or placement affects the perceived change in length.