Psychology -> Ponzo

Ponzo

ANIMATION

This illusion, also known as the railway illusion, appears to result from the same visual perceptual principles at work in the Muller-Lyer and moon illusions.

The upper and lower horizontal lines are the same length but the upper one appears longer. This illusion probably occurs because the converging lines on either side convey linear perspective and provide a sense of distance, suggesting that the upper line is further away. Just as in the Muller-Lyer illusion, we think that if two lines cast equally long retinal images, but one seems further away, the more distant one is assumed to be longer. Thus, the Ponzo illusion is due largely to a combination of the misapplication of size constancy and the misperception of depth.