Persistence of vision is the optical illusion that occurs when the visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye. The illusion has also been described as "retinal persistence", "persistence of impressions", simply "persistence" and other variations. A very commonly given example of the phenomenon is the apparent fiery trail of a glowing coal or burning stick while it is whirled around in the dark.
In visual perception, an optical illusion is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; their categorization is difficult because the underlying cause is often not clear but a classification proposed by Richard Gregory is useful as an orientation. According to that, there are three main classes: physical, physiological, and cognitive illusions, and in each class there are four kinds: Ambiguities, distortions, paradoxes, and fictions. A classical example for a physical distortion would be the apparent bending of a stick half immerged in water; an example for a physiological paradox is the motion aftereffect. An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion. Physical illusions are caused by the physical environment, e.g. by the optical properties of water. Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type. Cognitive visual illusions are the result of unconscious inferences and are perhaps those most widely known.
The term phi phenomenon is used in a narrow sense for an apparent motion that is observed if two nearby optical stimuli are presented in alternation with a relatively high frequency. In contrast to beta movement, seen at lower frequencies, the stimuli themselves do not appear to move. Instead, a diffuse, amorphous shadowlike something seems to jump in front of the stimuli and occlude them temporarily. This shadow seems to have nearly the color of the background. Max Wertheimer first described this form of apparent movement in his habilitation thesis, published 1912, marking the birth of Gestalt psychology.
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek στρόβος (stróbos), meaning "act of whirling".
Apparent motion may refer to:
The phenakistiscope was the first widespread animation device that created a fluid illusion of motion. Dubbed Fantascope and Stroboscopische Scheiben by its inventors, it has been known under many other names until the French product name Phénakisticope became common. The phenakistiscope is regarded as one of the first forms of moving media entertainment that paved the way for the future motion picture and film industry. Similar to a GIF animation, it can only show a short continuous loop.
The term beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one figure moving.
A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually, the rate of the stroboscope is adjustable to different frequencies. When a rotating or vibrating object is observed with the stroboscope at its vibration frequency, it appears stationary. Thus stroboscopes are also used to measure frequency.
The stroboscopic effect is a visual phenomenon caused by aliasing that occurs when continuous rotational or other cyclic motion is represented by a series of short or instantaneous samples at a sampling rate close to the period of the motion. It accounts for the "wagon-wheel effect", so-called because in video, spoked wheels sometimes appear to be turning backwards.
The wagon-wheel effect is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation.
The motion aftereffect (MAE) is a visual illusion experienced after viewing a moving visual stimulus for a time with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original stimulus. The motion aftereffect is believed to be the result of motion adaptation.
The peripheral drift illusion (PDI) refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery. This illusion was first described by Faubert and Herbert (1999), although a similar effect called the "escalator illusion" was reported by Fraser and Wilcox (1979). A variant of the PDI was created by Kitaoka Akiyoshi and Ashida (2003) who took the continuous sawtooth luminance change, and reversed the intermediate greys. Kitaoka has created numerous variants of the PDI, and one called "rotating snakes" has become very popular. The latter demonstration has kindled great interest in the PDI.
In human perception, contingent aftereffects are illusory percepts that are apparent on a test stimulus after exposure to an induction stimulus for an extended period. Contingent aftereffects can be contrasted with simple aftereffects, the latter requiring no test stimulus for the illusion/mis-perception to be apparent. Contingent aftereffects have been studied in different perceptual domains. For instance, visual contingent aftereffects, auditory contingent aftereffects and haptic contingent aftereffects have all been discovered.
Stuart M. Anstis is a professor emeritus of psychology at the University of California, San Diego, in the United States.
Illusions of self-motion occur when one perceives bodily motion despite no movement taking place. One can experience illusory movements of the whole body or of individual body parts, such as arms or legs.
Akiyoshi Kitaoka is a Professor of Psychology at the College of Letters, Ritsumeikan University, Kyoto, Japan, who has been referred to as "a master of optical art".
Simon Ritter von Stampfer, in Windisch-Mattrai, Archbishopric of Salzburg today called Matrei in Osttirol, Tyrol – 10 November 1864 in Vienna) was an Austrian mathematician, surveyor and inventor. His most famous invention is that of the stroboscopic disk which has a claim to be the first device to show moving images. Almost simultaneously, a similar device was developed in Belgium.
Due to the effect of a spatial context or temporal context, the perceived orientation of a test line or grating pattern can appear tilted away from its physical orientation. The tilt illusion (TI) is the phenomenon that the perceived orientation of a test line or grating is altered by the presence of surrounding lines or grating with a different orientation. And the tilt aftereffect (TAE) is the phenomenon that the perceived orientation is changed after prolonged inspection of another oriented line or grating.
Motion silencing is an illusion or perceptual phenomenon in which objects that are rapidly changing in a particular salient property seem to cease changing with motion. The illusion was first identified by Jordan Suchow and George Alvarez in the publication of their research on the topic.
