Pulfrich Phenomenoneffect

The German physicist/psychologist Carl Pul-frich (1858-1927) described this visual stereoscopic effect/illusion in 1922; ironically, Pul-frich was born blind in one eye and never himself experienced stereoscopic vision or "stereopsis." The Pulfrich illusion/effect may be experienced when a pendulum - such as a string with a weight attached to one end - is swung from side to side in a plane perpendicular to the viewer's line of vision. If such a stimulus is viewed from a distance with a dark lens (as with a pair of sunglasses or dark filter over one eye but with both eyes open, and attending to the center of the swing), the pendulum seems to move in an ellipse that is parallel to the floor. The pendulum appears to swing clockwise when viewed from above if the dark lens covers the left eye, but counterclockwise if the dark lens covers the right eye. Also, a "kinephantom," or misperception of visual movement, may occur when any object moves across the viewer's line of vision (and where the dark filter covers the left eye), with the result that objects moving from left to right (say on a television screen) appear to recede, whereas objects moving from right to left on a screen seem to be displaced forward. For the description of various other effects and illusions, see Appendix A. See also PERCEPTION (I. GENERAL), THEORIES OF. REFERENCES

Pulfrich, C. (1922). Die stereoskopie im dienste der isochromen und heterochro-men photometrie. Naturwissenschaften, 10, 533-564, 569-601, 714-722, 735-743, 751-761. Rosemann, H., & Buchmann, H. (1953). The explanation of the Pulfrich effect. Zeitschrift fur Biologie, 106, 71-76. [See also (1952), 105, 134-146].

Weale, R. A. (1954). Theory of the Pulfrich effect. Ophthalmologica (Basel), 128, 380-388. Morgan, M. J., & Thompson, P. (1975). Apparent motion and the Pulfrich effect. Perception, 4, 3-18. Mahmud, S. H. (1990). The Pulfrich effect: A new look. Psychological Studies, 35, 104-108. Ito, H. (2003). The aperture problems in the Pulfrich effect. Perception, 32, 367375.

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