Phi phenomenon

The phi phenomenon is a perceptual illusion, the Max Wertheimer to published in his 1912 article was first described in Experimental studies on the seeing of motion. It manifests itself as a form and formless perception of movement and is generated by a sequence of still images. In discussions about film and video, it is often confused with the beta motion, but is an independent phenomenon that is not to link directly to the perception of movement in movies.

The classic experiment on the phi phenomenon is carried out so that the subjects look at a screen projected on the alternating two still images. The first picture shows a line on the left side of the picture, the second on the right. The time in which the still images are displayed, may be varied. Finally, the subjects are asked for a description of what is seen.

In certain temporal and spatial intervals of the sequence images is created for the viewer the illusion of motion between the lines, even though these perceive the two individual lines yet been determined simultaneously, ie it does not give the impression of a single, permanently moving line, as in the beta movement. Instead one sees when phi phenomenon movement of a portion of the background color. The discovery of the phi phenomenon represents a milestone in the Gestalt psychology