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Encyclopedia > Visual perception
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In psychology, visual perception is the ability to interpret information from visible light reaching the eyes. The resulting perception is also known as eyesight, sight or vision. The various physiological components involved in vision are referred to collectively as the visual system. Psychological science redirects here. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... For other uses, see Eye (disambiguation). ... In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ... The visual system is the part of the nervous system which allows organisms to see. ...

Contents

Visual system

Main article: Visual system

The visual system in humans allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain. The visual system is the part of the nervous system which allows organisms to see. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... Human eye cross-sectional view. ... For other uses, see Brain (disambiguation). ... This article is about transducers in engineering. ... Functional parts of the rods (rods) and cones (cones)[1] A photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eyes retina that is capable of phototransduction. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... A hierarchy (in Greek: , derived from — hieros, sacred, and — arkho, rule) is a system of ranking and organizing things or people, where each element of the system (except for the top element) is a subordinate to a single other element. ... Grays FIG. 719– Hind- and mid-brains; postero-lateral view. ... Brodmann area 17 (primary visual cortex) is shown in red in this image which also shows area 18 (orange) and 19 (yellow) The visual cortex refers to the primary visual cortex (also known as striate cortex or V1) and extrastriate visual cortical areas such as V2, V3, V4, and V5. ... For other uses, see Brain (disambiguation). ...


Study of visual perception

The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what we actually see.


Early studies on visual perception

The visual dorsal stream (green) and ventral stream (purple) are shown. Much of the human cerebral cortex is involved in vision.
The visual dorsal stream (green) and ventral stream (purple) are shown. Much of the human cerebral cortex is involved in vision.

There were two major Greek schools, providing a primitive explanation of how vision is carried out in the body. Image File history File links Ventral-dorsal_streams. ... Image File history File links Ventral-dorsal_streams. ... The dorsal stream is a pathway for visual information which flows through the visual cortex, the part of the brain which provides visual processing. ... The primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. ... For other uses, see Cortex. ...


The first was the "emission theory" which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If we saw an object directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory was championed by scholars like Euclid and Ptolemy and their followers. Emission theory has at least two meanings: First, it refers to Newtons proposal that light is emitted from luminous objects in the form of particles or corpuscles. ... For other uses, see Euclid (disambiguation). ... This article is about the geographer, mathematician and astronomer Ptolemy. ...


The second school advocated the so called the 'intromission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagators Aristotle, Galen and their followers, this theory seems to have touched a little sense on what really vision is, but remained only a speculation lacking any experimental foundation.



Ibn al-Haytham (Alhacen), the "father of optics", pioneered the scientific study of the psychology of visual perception in his influential Book of Optics in the 1000s, being the first scientist to argue that vision occurs in the brain, rather than the eyes. He pointed out that personal experience has an effect on what people see and how they see, and that vision and perception are subjective. He explained possible errors in vision in detail, and as an example, describes how a small child with less experience may have more difficulty interpreting what he/she sees. He also gives an example of an adult that can make mistakes in vision because of how one's experience suggests that he/she is seeing one thing, when he/she is really seeing something else.[1] Al-Haytham carried out many investigations and experiments on visual perception, translated and extended the work of Ptolemy on binocular vision and commented on the anatomical works of Galen.[2][3] (Arabic: أبو علي الحسن بن الحسن بن الهيثم, Latinized: Alhacen or (deprecated) Alhazen) (965 – 1039), was an Arab[1] Muslim polymath[2][3] who made significant contributions to the principles of optics, as well as to anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, visual perception, and to science in general with his introduction of the... For the book by Sir Isaac Newton, see Opticks. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... The title page of a 1572 Latin manuscript of Ibn al-Haythams Book of Optics The Book of Optics (Arabic: Kitab al-Manazir, Latin: De Aspectibus or Perspectiva) was a seven volume treatise on optics written by the Iraqi Muslim scientist Ibn al-Haytham (Latinized as Alhacen or Alhazen... Events Sweyn I of Denmark invades England. ... A scientist, in the broadest sense, refers to any person that engages in a systematic activity to acquire knowledge or an individual that engages in such practices and traditions that are linked to schools of thought or philosophy. ... In the scientific method, an experiment (Latin: ex- periri, of (or from) trying) is a set of observations performed in the context of solving a particular problem or question, to retain or falsify a hypothesis or research concerning phenomena. ... This article is about the geographer, mathematician and astronomer Ptolemy. ... Binocular vision is vision in which both eyes are used synchronously to produce a single image. ... For other uses, see Galen (disambiguation). ...


Leonardo DaVinci,1452-1519, was the first to recognize the special optical qualities of the eye. He wrote "The function of the human eye, ... was described by a large number of authors in a certain way. But I found it to be completely different." Leonardo redirects here. ...

Leonardo DaVinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly.
Leonardo DaVinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly.

His main experimental finding was that there is only a distinct and clear vision at the line of sight, the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the modern distinction between foveal vision and peripheral vision. When viewing a scene, as in optics, photography, or even hunting, the line of sight is the straight line between the observer and the target. ... Schematic diagram of the human eye, with the fovea at the bottom. ... Peripheral vision is a part of vision that occurs outside the very center of gaze. ...


Unconscious inference

Hermann von Helmholtz is often credited with the first study of visual perception in modern times. Helmholtz examined the human eye and found it very disappointing from an optical point of view. The erratic informations gathered via the eye seemed to him to make vision impossible. He therefore concluded that vision could only be the result of some form of unconscious inferences: a matter of making assumptions and conclusions from incomplete data, based on previous experiences. Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ... The term Modern Times is used by historians to loosely describe the period of time immediately following what is known as the Early Modern Times. ... Inference is the act or process of deriving a conclusion based solely on what one already knows. ...


Inference requires prior experience of the world: examples of well-known assumptions - based on visual experience - are:

  • light comes from above
  • objects are normally not viewed from below
  • faces are seen upright[4]

The study of visual illusions (cases when the inference process goes wrong) has yielded much insight into what sort of assumptions the visual system makes. An optical illusion is any illusion that deceives the human visual system into perceiving something that is not present or incorrectly perceiving what is present. ...


Another type of the unconscious inference hypothesis ( based on probabilities) has recently been revived in so-called Bayesian studies of visual perception. Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a perception from sensory data. Models based on this idea have been used to describe various visual subsystems, such as the perception of motion or the perception of depth.[5][6] Bayesian refers to probability and statistics -- either methods associated with the Reverend Thomas Bayes (ca. ... Bayesian inference is statistical inference in which evidence or observations are used to update or to newly infer the probability that a hypothesis may be true. ... This article or section is in need of attention from an expert on the subject. ... Depth perception is the visual ability to perceive the world in three dimensions. ...


Gestalt theory

Main article: Gestalt psychology

Gestalt psychologists working primarily in the 1930s and 1940s raised many of the research questions that are studied by vision scientists today. Gestalt psychology (also Gestalt theory of the Berlin School) is a theory of mind and brain that proposes that the operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies; or, that the whole is greater than the sum of its parts. ... Gestalt psychology (also Gestalt theory of the Berlin School) is a theory of mind and brain that proposes that the operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies; or, that the whole is greater than the sum of its parts. ...


The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. Gestalt is a German word that translates to "configuration or pattern". According to this theory, there are six main factors that determine how we group things according to visual perception: Proximity, Similarity, Closure, Symmetry, Common fate and Continuity.


The cognitive and computational approaches

The major problem with the Gestalt laws (and the Gestalt school generally) is that they are descriptive not explanatory. For example, one cannot explain how humans see continuous contours by simply stating that the brain "prefers good continuity". Computational models of vision have had more success in explaining visual phenomena and have largely superseded Gestalt theory. More recently, the computational models of Visual Perception[7] have been developed for Virtual Reality systems - these are closer to real life situation as they account for motion and activities which populate the real world. Through these models it is possible to better understand both the limitations as well as the wonders of the brain. Computational neuroscience is an interdisciplinary science that links the diverse fields of neuroscience, cognitive science, electrical engineering, computer science, physics and mathematics. ...



Regarding Gestalt influence on the study of visual perception, Bruce, Green & Georgeson conclude:

"The physiological theory of the Gestaltists has fallen by the wayside, leaving us with a set of descriptive principles, but without a model of perceptual processing. Indeed, some of their "laws" of perceptual organisation today sound vague and inadequate. What is meant by a "good" or "simple" shape, for example?" [8]

In the 1980's David Marr developed a multi-level theory of vision, which analysed the process of vision at different levels of abstraction. In order to focus on the understanding of specific problems in vision, he identified (with Tomaso Poggio) three levels of analysis: the computational, algorithmic and implementational levels. David Marr (January 19, 1945 - November 17, 1980) was a British neuroscientist and psychologist. ...


The computational level addresses, at a high level of abstraction, the problems that the visual system must overcome. The algorithmic level attempts to identify the strategy that may be used to solve these problems. Finally, the implementational level attempts to explain how these problems are overcome in terms of the actual neural activity necessary.


Marr suggested that it is possible to investigate vision at any of these levels independently. Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include:

  • a 2D or primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression.
  • a 2-1/2 D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth.
  • a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.[9]

Marr unfortunately died of leukemia in Cambridge, Massachusetts at the age of 35, but his theory provides an important framework for the continued investigation of vision. Leukemia or leukaemia (Greek leukos λευκός, white; aima αίμα, blood) is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation (production by multiplication) of blood cells, usually white blood cells (leukocytes). ... Location in Middlesex County in Massachusetts Coordinates: , Country State County Middlesex Settled 1630 Incorporated 1636 Government  - Type Mayor-City Council  - Mayor Kenneth Reeves (D) Area  - Total 7. ...


See also

Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. ... Motion perception is the process of inferring the speed and direction of objects that move in a visual scene given some visual input. ... Depth perception is the visual ability to perceive the world in three dimensions. ... An optical illusion is any illusion that deceives the human visual system into perceiving something that is not present or incorrectly perceiving what is present. ...

Disorders/Dysfunctions

Achromatopsia is the inability to see color. ... Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... Scotopic sensitivity syndrome, also known as Meares-Irlen syndrome or Irlen syndrome, is a broadly defined visual perceptual disorder affecting primarily reading and writing based activities. ...

Related Disciplines

Psychophysics is a subdiscipline of psychology dealing with the relationship between physical stimuli and their subjective correlates, or percepts. ... Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal Neuroscience is a field that is devoted to the scientific study of the nervous system. ... Cognitive science is usually defined as the scientific study either of mind or of intelligence (e. ... Optometry (Greek: optos meaning eye or vision and metria meaning measurement) is a doctoral degree health care profession concerned with eyes and related structures as well as vision, visual system and vision information processing in humans. ... This article is about the branch of medicine. ...

References

  1. ^ Bradley Steffens (2006). Ibn al-Haytham: First Scientist, Chapter 5. Morgan Reynolds Publishing. ISBN 1599350246.
  2. ^ Howard, I (1996). "Alhazen's neglected discoveries of visual phenomena". Perception 25: 1203-1217. 
  3. ^ Omar Khaleefa (1999). "Who Is the Founder of Psychophysics and Experimental Psychology?". American Journal of Islamic Social Sciences 16 (2). 
  4. ^ Hans-Werner Hunziker, Im Auge des Lesers, Transmedia Zürich 2006 ISBN 978-3-7266-0068-6
  5. ^ Mamassian, Landy & Maloney (2002)
  6. ^ A Primer on Probabilistic Approaches to Visual Perception
  7. ^ A.K.Beeharee - http://www.cs.ucl.ac.uk/staff/A.Beeharee/research.htm
  8. ^ Bruce, V., Green, P. & Georgeson, M. (1996). Visual perception: Physiology, psychology and ecology, 3rd, LEA, 110. 
  9. ^ Marr, D (1982). Vision: A Computational Investigation into the Human Representation and Processing of Visual Information. MIT Press. 

External links

The nervous system is a highly specialized network whose principal components are nerves called neurons. ... The human eye is the first element of a sensory system: in this case, vision, for the visual system. ... This article is about the senses of living organisms (vision, taste, etc. ... The traditional five senses in human kind are the senses of vision, hearing, taste, and smell, and touch. ... The visual system is the part of the nervous system which allows organisms to see. ... The auditory system is the sensory system for the sense of hearing. ... Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. ... A Chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. ... The olfactory system is the sensory system used for olfaction. ... Olfaction (also known as olfactics) refers to the sense of smell. ... The gustatory system is the sensory system that uses taste buds (or lingual papillae) on the upper surface of the tongue to provide information about the taste of food being eaten. ... For the social and aesthetic aspects of taste, see taste (sociology). ... Somatic sensation consists of the various sensory receptors that trigger the experiences labelled as touch or pressure, temperature (warm or cold), pain (including itch and tickle), and the sensations of muscle movement and joint position including posture, movement, and facial expression (collectively also called proprioception). ... A nociceptor is a sensory receptor that sends signals that cause the perception of pain in response to potentially damaging stimulus. ... A thermoreceptor is a sensory receptor that responds to temperature, primarily within the innocuous range. ... The vestibular system, or balance system, is the sensory system that provides the dominant input about movement and equilibrioception. ... A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. ... This article is about pressure in the physical sciences. ... Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. ... // Proprioception (PRO-pree-o-SEP-shun (IPA pronunciation: ); from Latin proprius, meaning ones own and perception) is the sense of the relative position of neighbouring parts of the body. ... In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. ...

  Results from FactBites:
 
Visual perception - Wikipedia, the free encyclopedia (1205 words)
Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it as the perception known as eyesight, sight or naked eye vision.
Some argue that the perception of depth also constitutes a sense, but others argue that this is really cognition (that is, post-sensory) function derived from having stereoscopic vision (two eyes) and is not a sensory perception as such.
The eye's retina performs the first stages of visual perception processing, with the remaining stages of visual perception occurring in the optic nerve, the lateral geniculate nucleus, and the visual cortex of the brain.
  More results at FactBites »

 
 

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