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8   perception
 

8 perception

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8   perception 8 perception Presentation Transcript

  • Visual Imagination
  • Perception What is perception?  Perception is a process by which the brain codifies and organizes sensory impulses. Why is perception important?  Perception is important because people’s thoughts and ultimately behavior is based on their ability to sort out sensory information.
  • Visual Perception deals with:  the mechanics of observation  the discrimination of color  the discrimination of shapes of things  the discrimination of patterns  the discrimination of scale and dimension of things  the discrimination of distance between objects  the discrimination of background and foreground  the discrimination of depth of field
  • When visual impulses leave the retina through the optic nerve, they cross over to their respective areas in the brain, from which they will be interpreted. The crossover are is called the optic chiasm.
  • From the optic chiasm the impulses continue their travel through the optic tract to the lateral geniculate nucleus, a clearing house, where superfluous visual information is discarded.
  • From the lateral geniculate nucleus, the impulses radiate to the primary visual cortex of the occipital lobe.
  • The Primary Visual Cortex is made up of a large number of “modules” that contain a large number of nerve cells that correspond to different aspects of the retina.
  • The retina is not evenly represented but, instead, more primary cortex is devoted to images at or near the fovea. Some nerve cells in a module respond only to lines of certain orientations, others respond only to motion, others to color, etc. The function of the primary cortex it to codify the basic features of the images it receives.
  • PERCEPTION is the process of identifying the sensory input, and categorizing it accordingly.
  • As a process perception tends to be similar among human beings. This does not mean, however, that all people observing the same thing perceive the same thing. Perception can be strikingly different from person to person depending on multiple factors such as: 1. Quality and efficiency of the vision apparatus (color blindness, etc.)
  • 2. Social and cultural adaptation (perspective and geometry)
  • 3. Chemical influences on the cerebral cortex. (Ex. use of mind altering drugs) LEFT - 20 th Century artist Louis Wein. Portraits of his cat over a period of time that he developed schizophrenia. ABOVE Photo taken while hallucinating.
  • 4. Personality characteristics of the observer. A. Motivation - perceiving what we want to perceive. B. Expectation - perceiving what we ought to perceive
  • 5. Methods of observation To grasp and identify visual impulses the eye relies heavily on methods of observation such as: Pursuit movements: following a moving object within a visual field. Hunters (skeet shooters) and athletes have more developed observation skills in this regard. Observe the path the jet of water takes from its origin to the end of the arc.
  • Seccades: short scanning movements used in casual or directed observation. During reading the eyes pause briefly on individual words or sets of words. The eye moves between fixations at a rate of 20 to 30 msecs (seccades). Notice that the eye stops are not always sequential.
  • The recording on the right shows the scan-path of the bust on the left over a period of three minutes.
  • The drawings on the right provide the subject matter that is scanned by two different observers on the left. Notice how each scans the drawings differently. Drawing Observer A Observer B
  • Scan-path showing how an individual will perceive the same subject matter differently if scanning for different things. 1 - looking at composition 3 - looking for age 5 - looking for dress 7 - looking for relationships
  • 6. Observation within different contexts
  • Hi Vishwall Imigmashun calss. Aoccdrnig to rceent rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the lrttees in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh? Eonjy, Gozvendn :)
  • 7. Observation patterns - Gestalt The next segment will deal with these in greater depth.
  • Scientists, psychologists in particular, have attempted to discover how the human visual system perceives and grasps entities. One of the earliest and intuitively most acceptable theories about perception was proposed by Wertheimer in 1923, and later elaborated by Koffka in 1935. These Gestaltists formulated the principles or “laws” of grouping or patterning.
  • Gestalt is a German word that means: a whole entity or entirety.
  • We see everything f or the f irst time. . We see everything for the first time.
  • Gestalt theory claims that problem solving is productive and reproductive. Reproductive problem solving draws on previous experiences whereas productive problem solving involves insight and restructuring of the problem. Reproductive problem solving could be a hindrance to finding a solution, since a person may fixate on the known aspects of a problem and so be unable to see novel interpretations that might lead to a solution.
  • GESTALT PRINCIPLES OF VISUAL ORGANIZATION • Figure-ground - Organization depends on what we see as figure (object) and what we perceive a ground (context). • Similarity - Objects that have similar characteristics are perceived as unit. • Proximity - Objects close together in space or time perceived as belonging together. • Continuity - We tend to perceive figures or objects as belonging together if they appear to form a continuous pattern. • Closure - We perceive figures with gaps in them to be complete. • Simplicity - We tend to impose the simplest, best fitting, interpretation to any stimulus. • Common Fate - Visually perceived images that move toward each other are seen as forming a common object.
  • GESTALT PRECEPTS  The whole is greater than the sum of its parts.  Reality is different than perception  Experience changes perception
  • Figure vs. Ground One of the fundamental issues in visual perception concerns how we look at a scene or an image and determine what is the object of interest – figure, and what is ground the context the figure occurs in - ground. Edges and contours are usually critical in this respect and will often provide good information
  • Figure vs. Ground
  • Figure vs. Ground
  • Figure vs. Ground
  • Figure vs. Ground
  • Figure vs. Ground
  • Figure vs. Ground An issue related to figure/ground is the following. As we have observed visual scenes can be somewhat ambiguous, and can be seen in different ways. What are the cues that allow us to see one perspective over another? Is the picture on the left a picture of a young stylish woman, or of an old woman?
  • Similarity Items that look similar will be seen as parts of the same form. Do you see columns or rows?
  • Similarity Similar objects are seen as independent entities.
  • Proximity Things that are relatively close to one another tend to be grouped together
  • Proximity When elements are arranged in groups that define an object, we tend to see the object and not the elements.
  • Proximity The cluster has a separate identity outside the organized group.
  • Continuity The tendency to perceive unseen parts of a patterns as continuing in a predictable and simple manner.
  • Continuity Continuity of shape Continuity of line
  • Continuity An assumption is made that a certain continuity exists due to generalization.
  • Continuity
  • Closure An object may be partly occluded by other objects in our environment. The visual system fills in the missing information
  • Closure The mind has an uncanny ability to imagine shapes where there are none
  • Closure The mind has an uncanny ability to distinguish form from inadequate cues.
  • Closure
  • Closure In the 1950’s this photograph of a shadow formed by a tree caused quite a stir in Argentina.
  • Symmetry: regions bounded by symmetrical borders tend to be perceived as coherent figures
  • Continuity and Closure What does the sign say?
  • Common Fate Visually perceived images that move toward each other are seen as forming a common object. This principle is best imagined in terms of those animals you see on nature shows that seem to perfectly blend into their background, until they move. Then suddenly they appear visible.
  • Common Fate
  • Common Fate
  • Common Fate
  • Common Fate
  • Simplicity We tend to impose the simplest, best fitting, interpretation to any stimulus. In the image on the left, we tend to reduce the figures to the simplest shapes.