Poggendorff Illusion

Poggendorff Illusion

What is it?

The Poggendorff illusion is an optical illusion where two lines, one diagonal and one horizontal, are interrupted by a rectangle. The diagonal line appears to be discontinuous and misaligned with the horizontal line, leading to a perceived shift in the position of the diagonal line.

The Poggendorff Illusion is a visual illusion where our perception of the alignment of two straight lines appears to be distorted when they are partially hidden by an intervening shape, usually a rectangle or a set of parallel lines. This illusion was discovered by Johann Poggendorff, a German physicist, in 1860.

Here's a simple explanation using an example:

Imagine you have two straight lines, one above the other, with a small gap between them. They are perfectly aligned, continuing in the same direction, like the broken lines on a road. Now, picture a rectangle placed vertically on top of these lines, covering the middle portion of both lines. In this scenario, the lines appear to be misaligned or offset from one another, even though they are actually perfectly aligned.

The Poggendorff Illusion occurs because our brain has difficulty accurately processing the spatial relationships between the visible parts of the lines and the edges of the intervening shape. As a result, our perception of the continuation of the lines becomes distorted.

In everyday life, you might encounter the Poggendorff Illusion while looking at a fence with horizontal slats partially obscuring an object b ...