Category:Graphic design

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Graphic design is the applied art of arranging image and text to communicate a message. It may be applied in media such as print, electronic media, motion picture, animation, packaging, signs, identities, etc.

Resources:

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Wikipedia:Graphic Lab/Image workshop See the resource list at commons:Category:Charts.

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A

[+] Albums by cover artist (16 C)

C

[+] Color (13 C, 130 P)

F

[×] Film and television opening sequences (14 P)

G

[×] Graphic design studios (61 P)

[+] Graphic designers (12 C, 115 P)

[+] Graphics (1 C, 17 P)

I

[+] Infographics (13 C, 88 P, 1 F)

L

[+] Lithography (1 C, 7 P)

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N

[+] News design (1 C, 5 P)

P

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[+] Printing (19 C, 108 P)

P cont.

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S

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Pages in category "Graphic design"

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List of typefaces Morris Fuller Benton

(list of types) List of typefaces

designed by Frederic Goudy

2

291 (magazine)

7

75B

A

A.B. Dick Company AIGA Above the fold Adobe Certified

Instructor Adobe Creative Suite Adobe Dreamweaver Adobe GoLive Adobe ImageReady Adobe InDesign Adobe PhotoDeluxe Adobe Photoshop Advertising Aircraft livery American Graphics

Institute Anatomy of a

Typeface AndreaMosaic Ascender Corporation The Association of

Registered Graphic Designers of Ontario

AutoCollage 2008

B

Baseline (magazine) Bauhaus Bézier curve Book design Bookbinding Brand Brand architecture Brand implementation Breaking Boredom

Project

C

Cartographic generalization

Centerfold

D cont.

Dual City Sessions

E

Eighty Years of Book Cover Design

Paul Elliman Emigre (magazine) Exhibition designer Experimental Jetset Eye (magazine)

F

Trailer (film) First Things First 1964

manifesto First Things First 2000

manifesto Font Bureau Font Fusion FontShop FSI FontShop International Futura (typeface)

G

Gastrotypographicalassemblage Gestalt psychology Gestalten GIMP Graphic design Graphic Exchange Magazine Graphic Thought Facility Graphic arts Graphex Graphic design occupations Graphics Graphics coordinator Graphis Inc. Grid (page layout)

H

HTMLButcher Julia Hasting History of graphic design Will Holder (designer) Hoofdletters, Tweeling- en

Meerlingdruk House Industries

I

Icograda Ideogram Ikarus (typography software) Illustration Image Image editing

L cont.

Logoworks Ludlow Typograph

M

Modern typography

Monotype Corporation

Motion graphic design

N

Naked light News Illustrated News design

P

Page layout Page numbering Pantone Paste up The Penrose

Annual Persuasion design Pioneers of Modern

Typography Pixelmator Plazm (magazine) Portrait

Professional Postage stamp

design Poster Premedia Prepress Principles of User

Interface Design Print (magazine) Publishing

Interchange Language

Push Pin Studios

Q

Quark, Inc. QuarkXPress

R

Rich black Rubylith

S

St Bride Library

Clip art Colophon (publishing) Commercial art Communicate

knowledge manifesto Communicate:

Independent British Graphic Design since the Sixties

Communication Arts (magazine)

Cooper–Hewitt, National Design Museum

Corporate design Cover art Creative Review Crowdspring

D

DOT pictograms Design Can Change Design computing Design history Design Museum Design Observer Desktop Publishing

Magazine Desktop publishing Die cutting (web) Dieline Do Good Design Dot Dot Dot

(magazine)

Information design Information graphics Inprint International Typographic Style Intertype Corporation Isotype (picture language)

K

Sujata Keshavan Kusazōshi

L

LAID Letterpress printing Ligature Design Symposium Line art Linotype machine List of Baseline magazine issues List of Emigre magazine issues List of style guides Lithography

Salazar Awards Schule für

Gestaltung Basel SilverFast Slicing (interface

design) Spartan (typeface) Stencil Stock illustration Style guide Sustainable

graphic design

T

Thumbnail Transformation

playing card Type Directors

Club Type foundry Typeface Typographica Typography

U

User interface design

V

V4 Studios Vector graphics Vector packs Vignette (graphic

design) Visible Language Visual rhetoric Visualizer

(advertising) Volvelle

W

WebPlus Wordmark (graphic

identity)

Gestalt psychology

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Gestalt psychology or gestaltism (German: Gestalt - "essence or shape of an entity's complete form") of the Berlin School is a theory of mind and brain positing that the operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies. The Gestalt effect refers to the form-forming capability of our senses, particularly with respect to the visual recognition of figures and whole forms instead of just a collection of simple lines and curves. In psychology, gestaltism is often opposed to structuralism and Wundt. The phrase "The whole is greater than the sum of the parts" is often used when explaining Gestalt theory.[1]

Contents

[hide]

1 Origins 2 Theoretical framework and

methodology 3 Properties

o 3.1 Emergence o 3.2 Reification o 3.3 Multistability o 3.4 Invariance

4 Prägnanz 5 Gestalt views in psychology 6 Applications in computer science 7 Criticism 8 See also 9 References 10 External links

[edit] Origins

The concept of Gestalt was first introduced in contemporary philosophy and psychology by Christian von Ehrenfels (a member of the School of Brentano). The idea of Gestalt has its roots in theories by Johann Wolfgang von Goethe, Immanuel Kant, and Ernst Mach. Max Wertheimer's unique contribution was to insist that the "Gestalt" is perceptually primary, defining the parts of which it was composed, rather than being a secondary quality that emerges from those parts, as von Ehrenfels's earlier Gestalt-Qualität had been.

Both von Ehrenfels and Edmund Husserl seem to have been inspired by Mach's work Beiträge zur Analyse der Empfindungen (Contributions to the Analysis of the Sensations, 1886), in formulating their very similar concepts of Gestalt and Figural Moment, respectively.

Early 20th century theorists, such as Kurt Koffka, Max Wertheimer, and Wolfgang Köhler (students of Carl Stumpf) saw objects as perceived within an environment according to all of their elements taken together as a global construct. This 'gestalt' or 'whole form' approach sought to define principles of perception -- seemingly innate mental laws which determined the way in which objects were perceived. It is based on the here and now, and in the way you view things. It can be broken up into two: figure or ground, at first glance do you see the figure in front of you or the background?

These laws took several forms, such as the grouping of similar, or proximate, objects together, within this global process. Although Gestalt has been criticized for being merely descriptive, it has formed the basis of much further research into the perception of patterns and objects ( Carlson et al. 2000), and of research into behavior, thinking, problem solving and psychopathology.

It should also be emphasized that Gestalt psychology is distinct from Gestalt psychotherapy. One has little to do with the other.

[edit] Theoretical framework and methodology

This article does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2009)

The investigations developed at the beginning of the 20th century, based on traditional scientific methodology, divided the object of study into a set of elements that could be analyzed separately with the objective of reducing the complexity of this object. Contrary to this methodology, the school of Gestalt practiced a series of theoretical and methodological principles that attempted to redefine the approach to psychological research.

The theoretical principles are the following:

Principle of Totality - The conscious experience must be considered globally (by taking into account all the physical and mental aspects of the individual simultaneously) because

the nature of the mind demands that each component be considered as part of a system of dynamic relationships.

Principle of psychophysical isomorphism - A correlation exists between conscious experience and cerebral activity.

Based on the principles above the following methodological principles are defined:

Phenomenon Experimental Analysis - In relation to the Totality Principle any psychological research should take as a starting point phenomena and not be solely focused on sensory qualities.

Biotic Experiment - The School of Gestalt established a need to conduct real experiments which sharply contrasted with and opposed classic laboratory experiments. This signified experimenting in natural situations, developed in real conditions, in which it would be possible to reproduce, with higher fidelity, what would be habitual for a subject.

[edit] Properties

The key principles of Gestalt systems are emergence, reification, multistability and invariance.[1]

[edit] Emergence

Emergence is the process of complex pattern formation from simpler rules. It is demonstrated by the perception of the Dog Picture, which depicts a Dalmatian dog sniffing the ground in the shade of overhanging trees. The dog is not recognized by first identifying its parts (feet, ears, nose, tail, etc.), and then inferring the dog from those component parts. Instead, the dog is perceived as a whole, all at once. However, this is a description of what occurs in vision and not an explanation. Gestalt theory does not explain how the percept of a dog emerges.

[edit] Reification

Reification

Reification is the constructive or generative aspect of perception, by which the experienced percept contains more explicit spatial information than the sensory stimulus on which it is based.

For instance, a triangle will be perceived in picture A, although no triangle has actually been drawn. In pictures B and D the eye will recognize disparate shapes as "belonging" to a single shape, in C a complete three-dimensional shape is seen, where in actuality no such thing is drawn.

Reification can be explained by progress in the study of illusory contours, which are treated by the visual system as "real" contours.

See also: Reification (fallacy)

[edit] Multistability

the Necker Cube and the Rubin vase, two examples of multistability

Multistability (or multistable perception) is the tendency of ambiguous perceptual experiences to pop back and forth unstably between two or more alternative interpretations. This is seen for example in the Necker cube, and in Rubin's Figure/Vase illusion shown here. Other examples include the 'three-pronged widget' and artist M. C. Escher's artwork and the appearance of flashing marquee lights moving first one direction and then suddenly the other. Again, Gestalt does not explain how images appear multistable, only that they do.

[edit] Invariance

Invariance

Invariance is the property of perception whereby simple geometrical objects are recognized independent of rotation, translation, and scale; as well as several other variations such as elastic deformations, different lighting, and different component features. For example, the objects in A in the figure are all immediately recognized as the same basic shape, which are immediately distinguishable from the forms in B. They are even recognized despite perspective and elastic deformations as in C, and when depicted using different graphic elements as in D. Computational theories of vision, such as those by David Marr, have had more success in explaining how objects are classified.

Emergence, reification, multistability, and invariance are not necessarily separable modules to be modeled individually, but they could be different aspects of a single unified dynamic mechanism.[citation needed]

[edit] Prägnanz

The fundamental principle of gestalt perception is the law of prägnanz (German for pithiness) which says that we tend to order our experience in a manner that is regular, orderly, symmetric, and simple. Gestalt psychologists attempt to discover refinements of the law of prägnanz, and this involves writing down laws which hypothetically allow us to predict the interpretation of sensation, what are often called "gestalt laws".[2] These include:

Law of ClosureLaw of Similarity

Law of Proximity

Law of Closure — The mind may experience elements it does not perceive through sensation, in order to complete a regular figure (that is, to increase regularity).

Law of Similarity — The mind groups similar elements into collective entities or totalities. This similarity might depend on relationships of form, color, size, or brightness.

Law of Proximity — Spatial or temporal proximity of elements may induce the mind to perceive a collective or totality.

Law of Symmetry (Figure ground relationships)— Symmetrical images are perceived collectively, even in spite of distance.

Law of Continuity — The mind continues visual, auditory, and kinetic patterns. Law of Common Fate — Elements with the same moving direction are perceived as a

collective or unit.

[edit] Gestalt views in psychology

Gestalt psychologists find it is important to think of problems as a whole. Max Wertheimer considered thinking to happen in two ways: productive and reproductive.[2]

Productive thinking is solving a problem with insight.

This is a quick insightful unplanned response to situations and environmental interaction.

Reproductive thinking is solving a problem with previous experiences and what is already known. (1945/1959).

This is a very common thinking. For example, when a person is given several segments of information, he/she deliberately examines the relationships among its parts, analyzes their purpose, concept, and totality, he/she reaches the "aha!" moment, using what is already known. Understanding in this case happens intentionally by reproductive thinking.

Other Gestalts psychologist Perkins believes insight deals with three processes:1) Unconscious leap in thinking.[2].2) The increased amount of speed in mental processing.3) The amount of short-circuiting which occurs in normal reasoning.[3]

Other views going against the Gestalt psychology are:1) Nothing-Special View2) Neo-Gestalts View3) The Three-Process View

Gestalt laws continue to play an important role in current psychological research on vision. For example, the object-based attention hypothesis[4] states that elements in a visual scene are first grouped according to Gestalt principles; consequently, further attentional resources can be allocated to particular objects.

Gestalt psychology should not be confused with the Gestalt therapy of Fritz Perls, which is only peripherally linked to Gestalt psychology. A strictly Gestalt psychology-based therapeutic method is Gestalt Theoretical Psychotherapy, developed by the German Gestalt psychologist and psychotherapist Hans-Jürgen Walter.

[edit] Applications in computer science

The Gestalt laws are used in user interface design. The laws of similarity and proximity can, for example, be used as guides for placing radio buttons. They may also be used in designing computers and software for more intuitive human use. Examples include the design and layout of a desktop's shortcuts in rows and columns. Gestalt psychology also has applications in computer vision for trying to make computers "see" the same things as humans do.[citation needed] http://www.interaction-design.org/encyclopedia/gestalt_principles_of_form_perception.html

[edit] Criticism

In some scholarly communities, such as cognitive psychology and computational neuroscience, Gestalt theories of perception are criticized for being descriptive rather than explanatory in nature. For this reason, they are viewed by some as redundant or uninformative. For example, Bruce, Green & Georgeson[5] conclude the following regarding Gestalt theory's influence on the study of visual perception:

"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?"

[edit] See also

Psychology portal

Gestalt therapy - often mistaken for Gestalt psychology Structural information theory Rudolf Arnheim Wolfgang Metzger Kurt Goldstein Pál Schiller Harkai Solomon Asch Hermann Friedmann James Tenney Graz School Important publications in gestalt psychology Mereology Optical illusion Pattern recognition (psychology) Pattern recognition (machine learning) Notan Amodal perception Phenomenology Gestalt collapse phenomenon (Gestalt collapse disorder) - Gestaltzerfall

[edit] References

1. ̂ David Hothersall: History of Psychology, chapter seven,(2004) 2. ^ a b c Sternberg, Robert, Cognitive Psychology Third Edition, Thomson Wadsworth© 2003. 3. ̂ Langley& associates, 1987; Perkins, 1981; Weisberg, 1986,1995”> 4. ̂ Scholl, B. J. (2001). Objects and attention: The state of the art. Cognition, 80(1-2), 1-46. 5. ̂ Bruce, V., Green, P. & Georgeson, M. (1996). Visual perception: Physiology, psychology

and ecology (3rd ed.). LEA. pp. 110.

[edit] External links

Gestalt Society of Croatia International Society for Gestalt Theory and its Applications - GTA Art, Design and Gestalt Theory Rudolf Arnheim: The Little Owl on the Shoulder of Athene Embedded Figures in Art, Architecture and Design On Max Wertheimer and Pablo Picasso On Esthetics and Gestalt Theory The World In Your Head - by Steven Lehar Gestalt Isomorphism and the Primacy of Subjective Conscious Experience - by Steven Lehar The new gestalt psychology of the 21st century The Pennsylvania Gestalt Center Nancy Schleich Gestalt Counseling Gestalt Theory

Pattern recognition (psychology)

From Wikipedia, the free encyclopediaJump to: navigation, search

This article does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2006)

Pattern recognition involves identification of faces, objects, words, melodies, etc. The visual system does more than just interpret forms, contours and colors. Pattern recognition refers to the process of recognizing a set of stimuli arranged in a certain pattern that is characteristic of that set of stimuli. Pattern recognition is an innate ability of animals.

Contents

[hide]

1 Theories of pattern recognition o 1.1 Template matching o 1.2 Prototype matching o 1.3 Feature analysis o 1.4 Recognition of components o 1.5 Top down and bottom up processing

2 Multiple discrimination scaling 3 See also

[edit] Theories of pattern recognition

Template matching Prototype matching Feature analysis Recognition by components Fourier analysis Bottom-up and top-down processing

[edit] Template matching

The incoming sensory information is compared directly to copies (templates) stored in the long term memory. These copies are stored in the process of our past experiences and learning.

Eg. A A A are all recognized as the letter A but not B.

Note: This does not allow for variation in letters unless there are templates for each variation.

[edit] Prototype matching

Prototype means a concept of average characteristics of a particular subject. It can be found throughout the world. For instance a concept of small animal with feathers, beak, two wings that can fly is a prototype concept of a crow, sparrow, hen, eagle, etc. Prototype matching, unlike template matching, does not emphasize a perfect match between the incoming stimuli and the stored concept in the brain.

[edit] Feature analysis

According to this theory, the sensory system breaks down the incoming stimuli into its features and processes the information. Some features may be more important for recognition than others. All stimuli have a set of distinctive features. Feature analysis proceeds through 4 stages.[citation needed]

1. Detection 2. Pattern dissection

3. Feature comparison in memory 4. Recognition

[edit] Recognition of components

Irving Biederman theorizes that every object is made up of geons—the building blocks of all objects (cylinders, cones, are combined in many ways: on top of, to the side, etc.).[citation needed]

[edit] Top down and bottom up processing

1. Top down processing can be seen as processing what one is perceiving using past information.It occurs when someone infers from a generalization,law etc. to conclude something about a particular example, instance, case etc.

2. Bottom up processing can be seen as starting with no knowledge on a subject.It is said to occur when one draws generalizations from particular examples, instances, cases etc. to capture commonalities between them.

Hierarchy of detectors:

1. Feature detectors — lowest and highest; respond to curves, edges, etc. 2. Geon detectors — activated by feature detectors 3. Higher level detectors — recognize combinations of features and geons

According to Biederman an individual on average is familiar with about 30,000 objects and recognizing them requires no more than 36 geons.[citation needed]

[edit] Multiple discrimination scaling

Template and feature analysis approaches to recognition of objects (and situations) have been merged / reconciled / overtaken by multiple discrimination theory. This states that the amounts in a test stimulus of each salient feature of a template are recognized in any perceptual judgment as being at a distance in the universal unit of 50% discrimination (the objective performance 'JND': Torgerson, 1958) from the amount of that feature in the template (Booth & Freeman, 1993, Acta Psychologica).

Optical illusion

From Wikipedia, the free encyclopediaJump to: navigation, search This article is about visual perception. For the Time Requiem album, see Optical Illusion (album).

An optical illusion. The square A is exactly the same shade of grey as square B. See Same color illusion

An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, tilt, color, movement), and cognitive illusions where the eye and brain make unconscious inferences. They can also be known as "mind games".

Contents

[hide]

1 Physiological illusions 2 Cognitive illusions 3 Explanation of cognitive illusions

o 3.1 Perceptual organization o 3.2 Depth and motion perception

o 3.3 Color and brightness constancies o 3.4 Object consistencies o 3.5 Future perception

4 Illusions 5 Artists 6 Cognitive processes hypothesis 7 Gallery 8 See also 9 Notes 10 References 11 External links

[edit] Physiological illusions

A scintillating grid illusion. Shape, position, colour, and 3D contrast converge to produce the illusion of black dots at the intersections.

Physiological illusions, such as the afterimages following bright lights, or adapting stimuli of excessively longer alternating patterns (contingent perceptual aftereffect), are presumed to be the effects on the eyes or brain of excessive stimulation of a specific type - brightness, tilt, color, movement, etc. The theory is that stimuli have individual dedicated neural paths in the early stages of visual processing, and that repetitive stimulation of only one or a few channels causes a physiological imbalance that alters perception.

The Hermann grid illusion and Mach bands are two illusions that are best explained using a biological approach. Lateral inhibition, where in the receptive field of the retina light and dark receptors compete with one another to become active, has been used to explain why we see bands of increased brightness at the edge of a color difference when viewing Mach bands. Once a receptor is active it inhibits adjacent receptors. This inhibition creates contrast, highlighting edges. In the Hermann grid illusion the gray spots appear at the intersection because of the inhibitory response which occurs as a result of the increased dark surround.[1] Lateral inhibition has also been used to explain the Hermann grid illusion, but this has been disproved.[citation needed]

[edit] Cognitive illusions

Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by Hermann Helmholtz. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions.

1. Ambiguous illusions are pictures or objects that elicit a perceptual 'switch' between the alternative interpretations. The Necker cube is a well known example; another instance is the Rubin vase.

2. Distorting illusions are characterized by distortions of size, length, or curvature. A striking example is the Café wall illusion. Another example is the famous Müller-Lyer illusion.

3. Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in M. C. Escher's Ascending and Descending and Waterfall. The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join.

4. Fictional illusions are defined as the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or a hallucinogen. These are more properly called hallucinations.

[edit] Explanation of cognitive illusions

[edit] Perceptual organization

Reversible figure and vase

Duck-Rabbit illusion

To make sense of the world it is necessary to organize incoming sensations into information which is meaningful. Gestalt psychologists believe one way this is done is by perceiving individual sensory stimuli as a meaningful whole.[2] Gestalt organization can be used to explain many illusions including the Duck-Rabbit illusion where the image as a whole switches back and forth from being a duck then being a rabbit and why in the figure-ground illusion the figure and ground are reversible.

Kanizsa triangle

In addition, Gestalt theory can be used to explain the illusory contours in the Kanizsa Triangle. A floating white triangle, which does not exist, is seen. The brain has a need to see familiar simple objects and has a tendency to create a "whole" image from individual elements.[2] Gestalt means "form" or "shape" in German. However, another explanation of the Kanizsa Triangle is based in evolutionary psychology and the fact that in order to survive it was important to see form and edges. The use of perceptual organization to create meaning out of stimuli is the principle behind other well-known illusions including impossible objects. Our brain makes sense of shapes and symbols putting them together like a jigsaw puzzle, formulating that which isn't there to that which is believable.

[edit] Depth and motion perception

Illusions can be based on an individual's ability to see in three dimensions even though the image hitting the retina is only two dimensional. The Ponzo illusion is an example of an illusion which uses monocular cues of depth perception to fool the eye.

Ponzo illusion

In the Ponzo illusion the converging parallel lines tell the brain that the image higher in the visual field is farther away therefore the brain perceives the image to be larger, although the two images hitting the retina are the same size. The Optical illusion seen in a diorama/false perspective also exploits assumptions based on monocular cues of depth perception. The M. C. Escher painting Waterfall exploits rules of depth and proximity and our understanding of the physical world to create an illusion.

Like depth perception, motion perception is responsible for a number of sensory illusions. Film animation is based on the illusion that the brain perceives a series of slightly varied images produced in rapid succession as a moving picture. Likewise, when we are moving, as we would be while riding in a vehicle, stable surrounding objects may appear to move. We may also perceive a large object, like an airplane, to move more slowly, than smaller objects, like a car, although the larger object is actually moving faster. The Phi phenomenon is yet another example of how the brain perceives motion, which is most often created by blinking lights in close succession.

[edit] Color and brightness constancies

Simultaneous Contrast Illusion. The background is a colour gradient and progresses from dark grey to light grey. The horizontal bar appears to progress from light grey to dark grey, but is in fact just one colour.In this illusion, the colored regions appear rather different, roughly orange and brown. In fact they are the same colour, and in identical immediate surrounds, but the brain changes its assumption about colour due to the global interpretation of the surrounding image. Also, the white tiles that are shadowed are the same colour as the grey tiles outside the shadow.

Perceptual constancies are sources of illusions. Colour constancy and brightness constancy are responsible for the fact that a familiar object will appear the same colour regardless of the amount of or colour of light reflecting from it. An illusion of colour or contrast difference can be created when the luminosity or colour of the area surrounding an unfamiliar object is changed. The contrast of the object will appear darker against a black field that reflects less light compared to a white field even though the object itself did not change in colour. Similarly, the eye will compensate for colour contrast depending on the colour cast of the surrounding area.

[edit] Object consistencies

Like color, the brain has the ability to understand familiar objects as having a consistent shape or size. For example a door is perceived as rectangle regardless as to how the image may change on the retina as the door is opened and closed. Unfamiliar objects, however, do not always follow the rules of shape constancy and may change when the perspective is changed. The Shepard illusion of the changing table[3] is an example of an illusion based on distortions in shape constancy.

[edit] Future perception

Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York says optical illusions are due to a neural lag which most humans experience while awake. When light hits the retina, about one-tenth of a second goes by before the brain translates the signal into a visual perception of the world. Scientists have known of the lag, yet they have debated over how humans compensate, with some proposing that our motor system somehow modifies our movements to offset the delay.

Changizi asserts that the human visual system has evolved to compensate for neural delays, generating images of what will occur one-tenth of a second into the future. This foresight enables human to react to events in the present. This allows humans to perform reflexive acts like catching a fly ball and to maneuver smoothly through a crowd.[4] Illusions occur when our brains attempt to perceive the future, and those perceptions don't match reality. For example, one illusion called the Hering illusion, looks like bike spokes around a central point, with vertical lines on either side of this central, so-called vanishing point. The illusion tricks us into thinking we are moving forward, and thus, switches on our future-seeing abilities. Since we aren't actually moving and the figure is static, we misperceive the straight lines as curved ones.

Changizi said:

"Evolution has seen to it that geometric drawings like this elicit in us premonitions of the near future. The converging lines toward a vanishing point (the spokes) are cues that trick our brains into thinking we are moving forward - as we would in the real world, where the door frame (a pair of vertical lines) seems to bow out as we move through it - and we try to perceive what that world will look like in the next instant." [4]

[edit] Illusions

Main article: List of optical illusions

[edit] Artists

An optical illusion. The two circles seem to move when the viewer's head is moving forwards and backwards while looking at the black dot.

Floor tiles at the Basilica of St. John Lateran in Rome. The pattern creates an illusion of three-dimensional boxes.

The Spinning Dancer appears to move both clockwise and counter-clockwise

Artists have worked with optical illusions, including M. C. Escher, Bridget Riley, Salvador Dalí, Giuseppe Arcimboldo, Marcel Duchamp, Oscar Reutersvärd, Victor Vasarely and Charles Allan Gilbert. Also some contemporary artists are experimenting with illusions, including: Octavio Ocampo, Dick Termes, Shigeo Fukuda, Patrick Hughes (artist), István Orosz, Rob Gonsalves and Akiyoshi Kitaoka. Optical illusion is also used in film by the technique of forced perspective.

[edit] Cognitive processes hypothesis

The hypothesis claims that visual illusions are because the neural circuitry in our visual system evolves, by neural learning, to a system that makes very efficient interpretations of usual 3D scenes based in the emergence of simplified models in our brain that speed up the interpretation process but give rise to optical illusions in unusual situations. In this sense, the cognitive processes

hypothesis can be considered a framework for an understanding of optical illusions as the signature of the empirical statistical way vision has evolved to solve the inverse problem[5].

Research indicates that 3D vision capabilities emerge and are learned jointly with the planning of movements. After a long process of learning, an internal representation of the world emerges that is well adjusted to the perceived data coming from closer objects. The representation of distant objects near the horizon is less "adequate". In fact, it is not only the Moon that seems larger when we perceive it near the horizon. In a photo of a distant scene, all distant objects are perceived as smaller than when we observe them directly using our vision.

The retinal image is the main source driving vision but what we see is a "virtual" 3D representation of the scene in front of us. We don't see a physical image of the world. We see objects; and the physical world is not itself separated into objects. We see it according to the way our brain organizes it. The names, colors, usual shapes and other information about the things we see pop up instantaneously from our neural circuitry and influence the representation of the scene. We "see" the most relevant information about the elements of the best 3D image that our neural networks can produce. The illusions arise when the "judgments" implied in the unconscious analysis of the scene are in conflict with reasoned considerations about it.

[edit] Gallery

Stare at the center

Ebbinghaus illusion

Café wall illusion

Lilac chaser