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  1. 1. PERCEPTION Dr PS Deb MD, DM Neurology
  2. 2. SENSATION AND PERCEPTION •The process through which the senses pick up visual, auditory, and other sensory stimuli and Sensation transmit them to the brain; sensory information that has registered in the brain but has not been interpreted Perception •The process by which sensory information is actively organized and interpreted by the brain 2 7/11/2010 Perception
  3. 3. NAÏVE REALISM 7/11/2010 1. There exists a world of material objects. 2. Statements about these objects can be known to be true through sense- Perception experience. 3. These objects exist not only when they are being perceived but also when they are not perceived. 4. The objects of perception are largely perception-independent. 5. These objects are also able to retain properties of the types we perceive them as having, even when they are not being perceived. Their properties are perception-independent. 3
  4. 4. INDIRECT/DIRECT (NAÏVE) REALISM 7/11/2010  Hallucination and illusions cannot be Perception explained by direct realism  Object of world lies independent of sensory image and perception by brain 4
  5. 5. EPISTEMOLOGICAL DUALISM Whether the world • Representative realism claims we see around us is that we are directly aware only of the real world itself, internal representations of the or merely an external world, as objects are internal perceptual hidden behind a "veil of copy of that world perception". generated • Idealism asserts that no world by neural processes exists apart from mind-dependent in our brain ideas. 5 7/11/2010 Perception
  6. 6. EXTERNALISM AND INTERNALISM • Externalists think that factors deemed "external", meaning outside of the Externalism psychological states of those who gain knowledge, can be conditions of knowledge • all knowledge-yielding conditions are Internalism within the psychological states of those who gain knowledge. 6 7/11/2010 Perception
  7. 7. SENSATION AND PERCEPTION Sensation Input Processing Output Perception Brain Sense Environment 7 7/11/2010 Perception
  8. 8. SENSATION -> PERCEPTION • a) sensory organs absorb energy from a physical stimulus in the environment. Sensation • b) sensory receptors convert this energy into neural impulses and send them to the brain. Perception • a) the brain organizes the information and translates it into something meaningful. 8 7/11/2010 Perception
  9. 9. MEANINGFUL INFORMATION Selective • Process of discriminating between what is important & is irrelevant Attention and is influenced by motivation. Perceptual • How we perceive the world is a function of our past experiences, Expectancy culture, and biological makeup 9 7/11/2010 Perception
  10. 10. IN-ATTENTIONAL BLINDNESS 7/11/2010 Perception 10
  11. 11. TYPES OF PERCEPTION Sense perception Mental Perception 11 7/11/2010 Perception
  12. 12. GESTALT PSYCHOLOGY 7/11/2010 Perception The whole is different from the sum of its parts 12
  13. 13. PHI PHENOMENON 13 7/11/2010 Perception
  14. 14. AMBIGUOUS PHI PHENOMENON Which direction is she revolving? 14 7/11/2010 Perception
  15. 15. GESTALT PRINCIPLE OF PERCEPTUAL ORGANIZATION 1. Law of closure 2. Law of similarity 3. Law of proximity 4. Law of figure/ground 5. Law of good continuation 6. Law of simplicity 7. Law of common fate 15 7/11/2010 Perception
  16. 16. LAW OF CLOSURE  Humans tend to enclose a space by completing a contour and ignoring gaps in the figure 16 7/11/2010 Perception
  17. 17. LAW OF SIMILARITY  Elements that look similar will be perceived as part of the same form. There seems to be a triangle in the square 17 7/11/2010 Perception
  18. 18. LAW OF PROXIMITY Elements that are closer together will be perceived as a coherent object. 18 7/11/2010 Perception
  19. 19. LAW OF FIGURE/GROUND  A stimulus will be perceived as separate from it's ground The above figure appears to the eye as a square inside a circle, or as a donut shaped circle with a square hole 19 7/11/2010 Perception
  20. 20. LAW OF GOOD CONTINUATION  Humans tend to continue contours whenever the elements of the pattern establish an implied direction People tend to draw a good continuous line 20 7/11/2010 Perception
  21. 21. LAW OF SIMPLICITY (PRÄGNANZ)  A stimulus will be organized into symmetrical, simple, and regular. The above figure appears to the eye as a square overlapping triangle, not 21 a combination of several complicated shapes 7/11/2010 Perception
  22. 22. LAW OF COMMON FATE  Elements that move together tend to be grouped together 22 7/11/2010 Perception
  23. 23. EMERGENCE 7/11/2010  Emergence is the process of complex Perception pattern formation from simpler rules.  a Dalmatian dog sniffing the ground in the shade of overhanging trees. 23
  24. 24. HOW DO YOU SEE THE GLASS? Optimism Pessimism 24 7/11/2010 Perception
  25. 25. INFLUENCES ON PERCEPTION 7/11/2010  Perceptual set What do you see?  An expectation of Perception what will be perceived, which can affect what actually is Now what do you see? perceived 25
  26. 26. SEAT OF MINDS EYE  As humans, we have the ability to see with the mind's eye -to have a perceptual experience in the absence of visual input.  fMRI studies have shown that the lateral geniculate nucleus and the V1 area of the visual cortex are activated during mental imagery tasks  The visual pathway is not a one-way street. Higher areas of the brain can also send visual input back to neurons in lower areas of the visual cortex...  For example, PET scans have shown that when subjects, seated in a room, imagine they are at their front door starting to walk either to the left or right, activation begins in the visual association cortex, the parietal cortex, and the prefrontal cortex - all higher cognitive processing 26 centers of the brain 7/11/2010 Perception
  27. 27. VISUAL THINKING  A phenomenon of thinking through visual processing using the part of the brain that is emotional and creative to organize information in an intuitive and simultaneous way 27 7/11/2010 Perception
  28. 28. CONTROVERSY ABOUT VISUAL THINKING  Eidetic Memory: (photographic memory) may co-occur in visual thinkers as much as in any type of thinking style as it is a memory function associated with having vision rather than a thinking style.  Eidetic Memory can still occur in those with visual agnosia, who, unlike visual thinkers, may be limited in the use of visualization skills for mental reasoning. 28 7/11/2010 Perception
  29. 29. DYSLEXIA  As dyslexia is believed to affect up to 17% percent of the population and Visual thinking is predominant in around 60%-65% of the population, there is no clear indication of a link between visual thinking and dyslexia.  As visual thinking is the most common mode of thought, it might be expected that the incidence of visual thinking in the dyslexia community would be reflective of that in the general population, around 60%-65% of each population. 29 7/11/2010 Perception
  30. 30. AUTISM  Visual thinking has been argued by Temple Grandin to be an origin for delayed speech in people with autism.  However, picture thinking itself is only one form of "non-linguistic thinking" which includes physical (kinaesthetic), aural (musical) and logical (mathematical/systems) style of thought 30 7/11/2010 Perception
  31. 31. SPATIAL-TEMPORAL REASONING  Acute spatial ability is also a trait of kinesthetic learners (those who learn through movement, physical patterning and doing) and logical thinkers (mathematical thinkers who think in patterns and systems) who may not be strong visual thinkers at all.  Similarly, visual thinking has been described as seeing words as a series of pictures which, alone, is not exactly the same phenomena spatial- temporal reasoning. 31 7/11/2010 Perception
  32. 32. PERCEPTUAL CONSTANCY 7/11/2010  Perceptual constancy  The tendency to perceive objects as maintaining stable properties (e.g., size, shape, Perception brightness, and color) despite differences in distance, viewing angle, and lighting  Size constancy  Perceiving objects as being about the same size when they move farther away  Shape constancy  Perceiving objects as having a stable or unchanging shape regardless of changes in the retinal image resulting from differences in viewing angle 32
  33. 33. DEPTH PERCEPTION  Depth perception  The ability to see in three dimensions and to estimate distance  Binocular depth cues  Depth cues that depend on two eyes working together  Convergence  Occurs when the eyes turn inward to focus on nearby objects – the closer the object, the greater the convergence  Binocular disparity (or retinal disparity)  Difference between the two retinal images formed by the eyes’ slightly different views of the objects focused on 33 7/11/2010 Perception
  34. 34. ERROR OF PERCEPTION • Perception without Hallucination actual stimuli • An incorrect perception Illusion caused by a distortion of visual sensations 34 7/11/2010 Perception
  35. 35. MÜLLER-LYER ILLUSION 7/11/2010 The two lines above are the same length, but Perception the diagonals extending outward from both ends of the lower line make it look longer than the upper line 35
  36. 36. AMBIGUOUS IMAGE 7/11/2010  Ambiguous figures  Can be seen in Perception different ways to make different images  Best known ambiguous figure is “Old Woman/Young Woman,” by E. 36
  37. 37. IMPOSSIBLE FIGURES 7/11/2010  Do not seem unusual at first Perception  Figures that cannot be build. 37
  38. 38. ALICE IN WONDERLAND SYNDROME 7/11/2010  The eyes themselves are normal, but the sufferer 'sees' objects with the wrong Perception size or shape and/or finds that perspective is incorrect.  This can mean that people, cars, buildings, etc. look smaller or larger than they should be, or that distances look incorrect; for example a corridor may appear to be very long, or the ground may appear too close. 38
  39. 39. 7/11/2010 Perception THE END 39