Skip to main content icon/video/no-internet

An optical illusion that is based on the suggestion that the human mind judges an object's size based on its background. This was first demonstrated by the Italian psychologist Mario Ponzo in 1913 by drawing two straight lines across a pair of converging lines. The horizontal line on top tends to look longer than the one below it. This tendency is known as the Ponzo illusion. The upper line looks longer because we interpret the converging sides according to the linear perspective. The two lines cast the same-size retinal image, so the one that seems more distant is perceived to be larger. The more depth perception cues there are in the background, the stronger the illusion. For more information, see Deregowski (1989).

10.4135/9781412972024.n1933
locked icon

Sign in to access this content

Get a 30 day FREE TRIAL

  • Watch videos from a variety of sources bringing classroom topics to life
  • Read modern, diverse business cases
  • Explore hundreds of books and reference titles

Sage Recommends

We found other relevant content for you on other Sage platforms.

Loading