Poggendorff illusion

English

When lines are obscured by the grey rectangle, the blue line appears to be the continuation of the black line; in fact, as shown on the right, this is incorrect.

Etymology

Named after Johann Christian Poggendorff, journal editor who discovered the effect in figures submitted by Johann Karl Friedrich Zöllner in 1860.

Pronunciation

• Rhymes: -uːʒən

Noun

Poggendorff illusion (plural Poggendorff illusions)

1. An optical illusion involving the misperception of the position of one segment of a transverse line that has been interrupted by the contour of an intervening structure.