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September 22, 2013

Essay on Illusion in Sensation and Perception

Illusion in Sensation and Perception

An optical illusion is an illusion that deceives misinterpretation (no elephant) our brain that deceives the human visual system (from the eye to the brain) and leads to a distorted perception of reality. Optical illusions can occur naturally or be created by specific visual tricks that can highlight the operating principles of the human visual system. Illusions have much do with the sensation and perception. Illusion can be defined as a vehicle to understand them.  Although visual illusions, often times to as optical illusions, among the most known and reported, both in the scientific and public literature.  It should be noted that the phenomena of illusion are not limited only to the visual modality but are also observed in other modalities, such as hearing or touch. Some perceptual illusions involve the same number of sensory terms and are known as multi-modal illusions.(David, 2004)
Unlike the hallucination which is defined as a false perception, e.g. feeling immediate reality comparable to that of a real perception without real object, the illusion may be defined as the perception of "wrong" of a real object. The phenomena of illusion involve therefore directly building processes and perceptual interpretation of an object a perceptual scene.
The illusions have long been known, as illustrated by the famous illusion of Descartes:
If we cross the index and middle fingers, and we rolled a little ball of bread between two, it seems to be in contact with two balls of different bread! We experiment also in our lives every day, without even realizing it.
Just think of the moon illusion: the apparent size of the moon seems to depend on its position over the azimuth (it appears much larger when it is at the zenith), then when is not. This is a classic example of perceptual constancy, the mechanism by which we "adapt" our perception to the size of an object based on its distance. Another category of perceptual ambiguities, close to perceptual illusions, include all the phenomena of perceptual reality, in which the interpretation of the same object is compatible with two percepts. In some cases, we only perceive one of the two, then once the second revealed object is seen immediately in many other cases, we alternate between the two percepts, without ever being able to select one permanently.(Solso, 2001)
Most of the phenomena of visual perceptual illusions can be classified according to different categories, depending on the properties that are present in the visual object and which may have the ability to "trick" the eye. These are the geometric characteristics, the attributes of luminance or contrast, the identity of the object within the environment in which it is, or its dynamic properties - space and time - when the object is animated by a movement, for example.
The main types of visual illusions are as follows: geometric figures, the subjective contours, the transition effects of contrast, the effects of induced movement, figures distorted or ambiguous, figures camouflaged. The optical geometric illusions are based on simple objects, defined by lines or segments linked according to specific geometric configurations, which induce misinterpretation of these spatial relationships.(Breggin, 2001)
These are the first to be studied, by leading psychologists of the nineteenth century, and these are the ones that are cited most often when studying the phenomena of visual perceptual illusions (we do are no less than 200, including variants of classic illusions). They usually consist of an inductor and a neutral element, suffering the effects of deformation produced by the element inductor.
Other classifications have been proposed, such as that based on an analysis of  illusions and delusions that distinguishes the length (factor A) and effects on the surface, shape and direction of the lines (factor B) (David, 2004). The famous psychologist Jean Piaget has also proposed a distinction between primary and secondary illusions and delusions according to their sensitivity to age. The primary illusions diminish intensity with age, but never disappear completely. From a developmental point of view, they appear when the eye randomly sampled visual image: only certain regions.
This distinction has nevertheless been the subject of much criticism. For Piaget, however, the perceptual illusions are not "exceptions" to the normal perception but reflect our perception of objects and their relationships, which, unlike the other major cognitive function that is the intelligence, is essentially a mechanism for the distortion of reality.
Some illusions produce a linking of magnitude of the elements of FIG. The generally results in a contrast effect or accent differences between the stimuli: the apparent size of the largest elements is overestimated compared to smaller and vice versa.
Central is overestimated when arrowheads are directed outward to its present ends from the same segment associated with arrowheads facing inwards. In this case, rather it is a minimization of differences between stimuli, and assimilation parts to a whole: it equates to an element larger neighbor, causing overestimation. The contrast would intervene only when the perceived differences are too great.(Quinn, 2001)
These concepts are derived from the approach initiated by transactionalist Ames, but developed by Ittelson in the 1960's, who considered the perception of illusions, mainly optic geometrics, as a compromise for perception. The global percept results when more mechanisms assimilation or contrast occurs only to minimize or maximize the differences between elements to form a unitary percept. These phenomena are general, and would not necessarily be limited to the visual modality: when a cold hand plunges into hot water, it is much warmer than it actually is. But this dichotomy is strictly not accepted by all.
Another explanation for the illusion of MüllerLyer is on the analysis of eye movements, particularly spatial positions of fixation, which reveals fixation times higher in one of two configurations, which could explain the phenomenon of over-estimation by a simple mechanism of "averaging" space between the ends fixed: if the feathers are directed outward, the spatial distance between the ends is greater. Moreover, the overestimation is more important than the angle by the penne is more acute. This illusion seems to appeal to both the effects of linking of magnitude, but also the effects of angle. (Phelan, 2006)
Visual illusions are not limited to only those effects related to the geometrical configuration of segments or basic shapes, but can also involve other attributes of the visual image, like contrast transitions. Contrast sensitivity is the ability to distinguish differences in luminance in a visual scene. An object on a black white background can be defined as a transition zone of high contrast at its edges. The "brightness" of the same range increases the vicinity of a less intense light and decreases vicinity of an area more intense. The apparent clarity of a surface element depends not only on the intensity of the light from the region concerned but also the light on neighboring regions. Contrast phenomena occur to accentuate the differences between regions.
The theory of the gestalt approach follows the elementarist perception which was dominant in the late nineteenth century to the early twentieth century. This approach considers that the perception is equivalent to the addition of elementary sensations which are organized at some point in a structured whole. The ultimate collection based on the structure of these associations to the experience in a role as the individual learns to associate its various sensations of his experience to organize them into a coherent whole. He proposed the idea that we cannot perceive the melody as an elementary sensation. To describe a form one must consider the elements and relationships between elements.
Wertheimer marked the beginnings of the gestalt. In 1912, he worked on the apparent motion. The experiment consists of alternating light in the darkness two bright spots slightly apart are emerging in succession each of the two points in two separate locations in a slow pace, if we increase the pace it looks back and forth from a single point. For them, perception is an independent organization of sensation.(McGurk, 1976)
Perceptions are seen as corresponding to all-inclusive experiences; it is therefore considered that the sensation does not exist as a psychological reality. What is original in terms of the result is perceptual constancy.
Perceptions are conceived as innate. One of the problems of the senses and the relationship between perception and meaning is significant indeed. We know that we perceive objects if they have more meaning if they do not, so it is different than innate.
When one wants to study perception, we can consider that it depends on several factors (motivation, needs) but also structural factors related to the stimulation and sensory properties. The authors explained by saying that perception depends on the characteristics of stimulation in relation to the characteristics of the sensory nervous system of the individual.
At the visual cortex, the cortical centers operate in a global and non-independent (assumption). Today, Livingston and Aubette have shown that there are several different areas depending on the features such as the perceptual organization and problem of ambiguous images.
The perception cannot be reduced to something atomistic because it does not correspond to an elementary sensation. What we perceive is the global configurations constructed from their components. The Gestalt psychologists have tried to apply this reasoning to the act of thinking itself. These are the concepts of intellectual act that led Gestalt psychologist to greatly influence the emergence of cognitivism. (O’Conner, 2009)
First thing in common with gestalts, Piaget shows the importance of the notion of totality in the figure but the difference is that the total does not reflect an emergent property. The activity will consist of a perceptual matching of elements present. To account for this, it will discuss the primary effects, it is the interactions between different elements of a figure, each centering results in primary effects that correspond to an overestimation of items that are around the attachment points. These primary effects are distortions.(Yoon & Jackie 2008)
The theory is structural and functional. It is functional because it provides an essential role for the functioning of the subject that will help to correct the distortions that we have just discussed (primary effects).
The primary effects on corrects the perceptual activity that is characterized by a decentralization (changing fixation point), each new centre will allow to cancel the existing distortions. The primary effects are uncontrollable (cannot avoid them, they still exist), especially for all ages, their intensity will decrease with age, this is because the perceptual activity is subject to the level operation of the subject, it increases during development.
Gibson's theory focuses mainly on visual perception, the idea is that all the information necessary for perception are present in the environment and it will be for the observer to enter this information. This is made possible by the movement or objects or the observer himself.As gestalts, Gibson refuses to accept the distinction between sensation and perception as a psychological entity. He is interested in perception, distinction between distal and proximal stimulus. (Posner, K., Vaughan, B.S. & Kratochvil, 2008)
The proximal stimulus excites the sensory receptors, that is to say it is the light waves reflected from the object and come excite the eye, is accessed directly and can get information on the distal stimulus. For gestalts, the transition from one to another is by a process of organization, perceptual organization is necessary because the structure of the object and the subject must break out and reorganize its perceptions.









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