An Ames room is a distorted room that creates an optical illusion. Likely influenced by the writings of Hermann Helmholtz, [1] it was invented by American scientist Adelbert Ames Jr. in 1946, [2] and constructed in the following year.
An Ames room is a distorted room that creates an optical illusion. Likely influenced by the writings of Hermann Helmholtz, [1] it was invented by American scientist Adelbert Ames Jr. in 1946, [2] and constructed in the following year.
An Ames room is viewed with one eye through a peephole. Through the peephole, the room appears to be an ordinary rectangular cuboid, with a back wall that is vertical and at right angles to the observer's line of sight, two vertical side walls parallel to each other, and a horizontal floor and ceiling.
The observer will see that an adult standing in one corner of the room along the back wall appears to be a giant, while another adult standing in the other corner along the back wall appears to be a dwarf. An adult who moves from one corner of the room to the other appears to change dramatically in size.
The true shape of the room is that of an irregular hexahedron: depending on the design of the room, all surfaces can be regular or irregular quadrilaterals, so that one corner of the room is farther from an observer than the other.
The illusion of an ordinary room is because most information about the true shape of the room does not reach the observer's eye. The geometry of the room is carefully designed, using perspective, so that, from the peephole, the image projected onto the retina of the observer's eye is the same as that of an ordinary room. Once the observer is prevented from perceiving the real locations of the parts of the room, the illusion that it is an ordinary room occurs.
One key aspect of preventing the observer from perceiving the true shape of the room is the peephole. It has at least three consequences:
Other sources of information about the true shape of the room are also removed by its designer. For example, by strategic lighting, the true far corner is as bright as the true near corner. For another example, patterns on the walls (such as windows) and floor (such as a black-and-white chequerboard of tiles) can be made consistent with its illusory geometry.
The illusion is powerful enough to overcome other information about the true locations of objects in the room, such as familiar size. For example, although the observer knows that adults are all about the same size, an adult standing in the true near corner appears to be a giant, while another adult standing in the true far appears to be a dwarf. For another example, although the observer knows that an adult cannot change size, they see an adult who walks back and forth between the true far and true near corners appear to grow and shrink.
Studies have shown that the illusion can be created without using walls and a ceiling;[ citation needed ] it is sufficient to create an apparent horizon (which in reality will not be horizontal) against an appropriate background, and the eye relies on the apparent relative height of an object above that horizon.
The Ames room has as a predecessor, from as early as the 15th century, the movement in art called trompe-l'œil, [3] in which the artist creates the illusion of three-dimensional space, usually on a flat surface.
Ames's original design also contained a groove that was positioned such that a ball in it appears to roll uphill, against gravity. [4] Richard Gregory regarded this apparent "anti-gravity" effect as more amazing than the apparent size changes, although today it is often not shown when an Ames room is exhibited.
Gregory speculated that "magnetic hills" (also known as gravity hills) can be explained by this principle. For such a location in Ayrshire, Scotland, known as the Electric Brae, he found that a row of trees form a background similar to the setting of an Ames room, making the water in a creek appear to flow uphill. [4]
For Gregory, this observation raised particularly interesting questions about how different principles for understanding the world compete in our perception. The "anti-gravity effect" is a much stronger paradox than the "size change" effect, because it seems to negate the law of gravity which is a fundamental feature of the world. In contrast, the apparent size change is not such a strong paradox, because we do have the experience that objects can change size to a certain degree (for example, people and animals can appear to become smaller or larger by crouching or stretching).
A type of selective perceptual distortion known as the Honi phenomenon causes some married persons to perceive less size distortion of the spouse than a stranger in an Ames room.
The effect was related to the strength of love, liking, and trust of the spouse being viewed. Women who were high positive in this area perceived strangers as being more distorted than their partners. Size judgments by men did not seem to be influenced by the strength of their feeling toward their spouse. [5]
Further study has concluded that the Honi phenomenon does not reliably exist as first thought, but may be explained as sex difference influencing perception, with women interpreting a larger reading as a more meaningful or valuable perception of things than men's. [6]
The Ames room principle has been used widely in television and movie productions for special effects when it was necessary to show actors in giant size next to actors in small size. For example, production of The Lord of the Rings film trilogy used several Ames room sets in Shire sequences to make the heights of the diminutively sized hobbits correct when standing next to the taller Gandalf. [7]
When used for special effects, the viewers will not see that an Ames room is being used. However, a few times an Ames room has also been shown explicitly.
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 Müller-Lyer illusion is an optical illusion consisting of three stylized arrows. When viewers are asked to place a mark on the figure at the midpoint, they tend to place it more towards the "tail" end. The illusion was devised by Franz Carl Müller-Lyer (1857–1916), a German sociologist, in 1889.
Forced perspective is a technique that employs optical illusion to make an object appear farther away, closer, larger or smaller than it actually is. It manipulates human visual perception through the use of scaled objects and the correlation between them and the vantage point of the spectator or camera. It has uses in photography, filmmaking and architecture.
Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth perception happens primarily due to stereopsis and accommodation of the eye.
In the philosophy of perception and philosophy of mind, direct or naïve realism, as opposed to indirect or representational realism, are differing models that describe the nature of conscious experiences; out of the metaphysical question of whether the world we see around us is the real world itself or merely an internal perceptual copy of that world generated by our conscious experience.
The autokinetic effect is a phenomenon of visual perception in which a stationary, small point of light in an otherwise dark or featureless environment appears to move. It was first recorded in 1799 by Alexander von Humboldt who observed illusory movement of a star in a dark sky, although he believed the movement was real. It is presumed to occur because motion perception is always relative to some reference point, and in darkness or in a featureless environment there is no reference point, so the position of the single point is undefined. The direction of the movements does not appear to be correlated with involuntary eye movements, but may be determined by errors between eye position and that specified by efference copy of the movement signals sent to the extraocular muscles. Richard Gregory suggested that, with lack of peripheral information, eye movements which correct movements due to muscle fatigue are wrongly interpreted as movement of the perceived light.
The Ternus illusion, also commonly referred to as the Ternus Effect, is an illusion related to human visual perception involving apparent motion. In a simplified explanation of one form of the illusion, two discs, are shown side by side as the first frame in a sequence of three frames. Next a blank frame is presented for a very short, variable duration. In the final frame, two similar discs are then shown in a shifted position. Depending on various factors including the time intervals between frames as well as spacing and layout, observers perceive either element motion, in which L appears to move to R while C remains stationary or they report experiencing group motion, in which L and C appear to move together to C and R. Both element motion and group motion can be observed in animated examples to the right in Figures 1 and 2.
The Moon illusion is an optical illusion which causes the Moon to appear larger near the horizon than it does higher up in the sky. It has been known since ancient times and recorded by various cultures. The explanation of this illusion is still debated.
The term illusory motion, also known as motion illusion or "apparent motion", is an optical illusion in which a static image appears to be moving due to the cognitive effects of interacting color contrasts, object shapes, and position. The stroboscopic animation effect is the most common type of illusory motion and is perceived when images are displayed in fast succession, as occurs in movies. The concept of illusory motion was allegedly first described by Aristotle.
Entoptic phenomena are visual effects whose source is within the human eye itself.
Closed-eye hallucinations and closed-eye visualizations (CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They can be a form of phosphene. Some people report CEV under the influence of psychedelics; these are reportedly of a different nature than the "open-eye" hallucinations of the same compounds. Similar hallucinations that occur due to loss of vision are called visual release hallucinations.
The Ehrenstein illusion is an optical illusion of brightness or colour perception. The visual phenomena was studied by the German psychologist Walter H. Ehrenstein (1899–1961) who originally wanted to modify the theory behind the Hermann grid illusion. In the discovery of the optical illusion, Ehrenstein found that grating patterns of straight lines that stop at a certain point appear to have a brighter centre, compared to the background.
Subjective constancy or perceptual constancy is the perception of an object or quality as constant even though our sensation of the object changes. While the physical characteristics of an object may not change, in an attempt to deal with the external world, the human perceptual system has mechanisms that adjust to the stimulus.
The Ames trapezoid or Ames window is an image on, for example, a flat piece of cardboard that seems to be a rectangular window but is, in fact, a trapezoid. Both sides of the piece of cardboard have the same image. The cardboard is hung vertically from a wire so it can rotate around continuously, or is attached to a vertical mechanically rotating axis for continuous rotation. When the rotation of the window is observed, the window appears to rotate through less than 180 degrees, though the exact amount of travel that is perceived varies with the dimensions of the trapezoid. It seems that the rotation stops momentarily and reverses its direction. It is therefore not perceived to be rotating continuously in one section but instead is misperceived to be oscillating. This phenomenon was discovered by Adelbert Ames, Jr. in 1947.
Emmert's law states that objects that generate retinal images of the same size will look different in physical size if they appear to be located at different distances. Specifically, the perceived linear size of an object increases as its perceived distance from the observer increases. This makes intuitive sense: an object of constant size will project progressively smaller retinal images as its distance from the observer increases. Similarly, if the retinal images of two different objects at different distances are the same, the physical size of the object that is farther away must be larger than the one that is closer.
The Chubb illusion is an optical illusion or error in visual perception in which the apparent contrast of an object varies substantially to most viewers depending on its relative contrast to the field on which it is displayed. These visual illusions are of particular interest to researchers because they may provide valuable insights in regard to the workings of human visual systems.
In visual perception, the kinetic depth effect refers to the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving. In the absence of other visual depth cues, this might be the only perception mechanism available to infer the object's shape. Being able to identify a structure from a motion stimulus through the human visual system was shown by Hans Wallach and O'Connell in the 1950s through their experiments.
In human visual perception, the visual angle, denoted θ, subtended by a viewed object sometimes looks larger or smaller than its actual value. One approach to this phenomenon posits a subjective correlate to the visual angle: the perceived visual angle or perceived angular size. An optical illusion where the physical and subjective angles differ is then called a visual angle illusion or angular size illusion.
Geometrical–optical are visual illusions, also optical illusions, in which the geometrical properties of what is seen differ from those of the corresponding objects in the visual field.
The ambient optic array is the structured arrangement of light with respect to a point of observation. American psychologist James J. Gibson posited the existence of the ambient optic array as a central part of his ecological approach to optics. For Gibson, perception is a bottom-up process, whereby the agent accesses information about the environment directly from invariant structures in the ambient optic array, rather than recovering it by means of complex cognitive processes. More controversially, Gibson claimed that agents can also directly pick-up the various affordances of the environment, or opportunities for the observer to act in the environment, from the ambient optic array.
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