What is the Ponzo illusion and how does it work?

By overlaying two identical lines over a diminishing series of converging lines, like train tracks, the Ponzo Illusion tricks our brain into presuming that the upper of the two lines must be longer, because it appears—due solely to its background—to somehow be “in the distance.” So to be of anywhere near the same size …

What causes the Ponzo illusion?

In Figure 1 (Zöllner illusion), the horizontal lines appear slanted in the direction opposite the context lines. A new theory, called the tilt constancy theory, claims that the Ponzo illusion is caused by the mis- perception of orientation induced by local visual cues.

When did Mario Ponzo create the Ponzo illusion?

The Ponzo illusion is a geometrical-optical illusion that was first demonstrated by the Italian psychologist Mario Ponzo (1882–1960) in 1911. He suggested that the human mind judges an object’s size based on its background. He showed this by drawing two identical lines across a pair of converging lines,…

Why does the upper line look longer in the Ponzo illusion?

He suggested that the human mind judges an object’s size based on its background. He showed this by drawing two identical lines across a pair of converging lines, similar to railway tracks. The upper line looks longer because we interpret the converging sides according to linear perspective as parallel lines receding into the distance.

Can a blind person perceive the Ponzo illusion?

However, prior visual experience seems mandatory to perceive it as demonstrated by the fact that congenitally blind subjects are not sensitive to it. The Ponzo illusion has also been used to demonstrate a dissociation between vision-for-perception and vision-for-action (see Two-streams hypothesis ).

Which is an example of a geometrical illusion?

The Ponzo Illusion is one among a number of illusions where a central aspect of a simple line image—e.g. the length, straightness, or parallelism of lines—appears distorted by other aspects of the image—e.g. other background/foreground lines, or other intersecting shapes. These are sometimes called ‘geometrical-optical illusions’.