WINDMILL ILLUSION

windmill illusion: translation

Also known askinetic depth effect. The term windmill illusion was introduced in or shortly before 1860 by the German army physician Wilhelm Joseph Sinsteden (1803-1891). It refers to the inability to identify the direction of rotation of the revolving blades of a windmill when the blades are seen from a distance, and in silhouette. As seen from such a point of view, the apparent direction of rotation of the blades may reverse itself, until it is no longer possible to tell which is the true direction. The phenomenon itself was described as early as 1738 by the British mathematician Robert Smith (1689-1768). The windmill illusion is commonly classified as a *physiological illusion.

Miles, W.R. (1931). Movement interpretation of the silhouette ofa rotating fan.American Journal of Psychology, 48, 392-405.

Sinsteden, W.J. (1860). Über ein neues pseu-doskopisches Bewegungsphänomen.Poggen-dorffs Annalen der Physik und Chemie, 187, 336-339.