Artificial Scotoma

Perceptual illusion in which an artificial blind spot is filled in by a twinkling background.

Troxler Effect

Perceptual illusion in which an image in peripheral vision disappears.

Phenakistoscope

Optical toy producing the illusion of moving images, popular during the Victorian era.

Grey Man

Redirected to Brocken spectre.

Brocken spectre

Optical illusion in which the apparently greatly magnified shadow of an observer, when projected onto a surrounding mist, interferes with the observer’s depth perception.

Orgone

Widely discredited theory of universal life energy developed by the Austrian psychiatrist Wilhelm Reich (1897–1957).