Jastrow Illusion

The Jastrow illusion is an example of illusory perception of length: in this case, two white stripes are shown in two different positions. In the second picture, the upper stripe seems longer than in the first, but it has only been moved and not modified in any way.

This happens because, in the second picture, the distance between the left edges of the stripes is minimal, and our brain tends to "discount" or "round" it to zero, thus making the stripe look longer than it actually is. Some argue that the physiological mechanisms involved in this illusion are probably the base of the success of many types of make-up for women (for example to make eyelashes look longer).

Jastrow illusion: try comparing this image with the second image below.

The upper stripe seems longer than in the first image, but it is the same length (it was just moved slightly to the right)