Visual perception-illusions-paradoxes


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Visual perception-illusions-paradoxes

  1. 1. Visual Perception Illusions & Paradoxes d Priyadarshi Patnaik Associate ProfessorDepartment of Humanities & Social S iD fH ii S i l Sciences IIT Kharagpur
  2. 2. What about visuals?Many things which are visually communicated orperceived are biologically determinedBut many other things are learntVisuals communicate powerVisuals communicate emotionsVisuals communicate culture
  3. 3. The PanopticonJeremy Bentham (1785)Discipline and PunishParanoiaControlFearClose circuitEPR
  4. 4. Visuals and the Communication of Emotions
  5. 5. What is perception? Sensation + Interpretation
  6. 6. In philosophy psychology and the cognitive philosophy, psychology,sciences, perception is the process of attainingawareness or understanding of sensoryinformation. The word "perception" comesfrom the Latin words perceptio percipio and means perceptio, percipio,"receiving, collecting, action of takingpossession,possession apprehension with the mind orsenses."
  7. 7. When external stimuli is transmitted to our brainthrough our senses – sensationDevoid of any definition, any interpretation,meaningThe simplest building blockBut then it is taken up by the mind and analyzedMemory is stirred up remembering used up,Sensation identified, matched, given a name,defined,defined interpreted and remembered for futureuse
  8. 8. Part of what we perceive comes through thesenses from the objects before us; another partalways comes out of our own head William J Willi James
  9. 9. Subjective perception Image credit: Mark R. Homes @ National Geographic Society
  10. 10. To resolve ambiguities and make sense of theworld, the brain also creates shapes fromincomplete data. dataThe i lTh triangle you saw was d l d b I li developed by Italianpsychologist Gaetano Kanizsa.
  11. 11. IllusionImage credit: Mark R. Homes @ National Geographic Society
  12. 12. Illusion created because of “size constancy size constancy”effect to be discussed a little later.
  13. 13. OrientationImage credit: Mark R. Homes @ National Geographic Society
  14. 14. According to noted neuroscientist V. VRamachandran of University of California, SanDiego,Diego the brain can make guesses based oninformation available and some simpleassumptionsPattern of shadowsLightLi h usually from top ll f
  15. 15. Which are the concaves now?
  16. 16. Orientation
  17. 17. From the eye to the mind Retina 1 2 braineye 1: R l t ti 1 Relay station - LGN 2: Primary and more advanced area of visual cortex
  18. 18. Rods: Monochrome and in low lightCones: colour vision
  19. 19. AttentionThe perceptual process of selecting certaininputs for inclusion in our conscious experienceor awareness at any given time
  20. 20. Flash animationImage taken Flash Animation Software demo movie
  21. 21. FilteringWhy does focus shift?We filter, partly bl ki certain iW fil l blocking i inputs Limited Mental Capacity
  22. 22. Perception is taking in, filtering and interpretation tomake sense of the world. Memory and learning play animportant part, but so do certain innate organizationalabilities of the mind, highlighted by Gestaltpsychologists.The limits of my perception are the limits of my worldThe word is the world (since it takes us a step furtherand helps us cognize what we have perceived)
  23. 23. What we shall do nextForm perceptionColour perceptionDepthD h perception iThese will give us some idea of how and why wevisually perceive the many things that we do. yp y g
  24. 24. Form Perception and Gestalt G l
  25. 25. Gestalt (German) used to indicate the form- form-forming capabilities of the mind (Whole formapproach) and the belief that this holisticperception is innate to the mind
  26. 26. Figure-g ou dFigure-ground gu e M.C. Escher: Moebious with Birds
  27. 27. The visual system uses an innate binary division– the figure we look at and the ground which iseverything else and forms the backgroundThis relation is reversibleButB we cannot perceive the same thing as fi i h hi figureand ground at the same time – it requires amental switching l i hi
  28. 28. GestaltMax WertheimerKurt KoffkaWolfgang K hlW lf KohlerWe are surrounded by sounds and forms that donot have a sole meaning. At any moment, our g y ,perception is what gives it form and meaning.
  29. 29. What do we have here? Twelve lines 4 vertical 4 horizontal 4 oblong
  30. 30. The vase and the two facesA demonstration of multi-stability: popping back and forthbetween two or more unstable perceptions
  31. 31. Organization in form perception The whole is more than the sum of its h h fi parts
  32. 32. A Poem A Black CoatIt was a dark evening d k i Simple Life
  33. 33. Subjective Contour/Reification Image credit: Mark R. Homes @ National Geographic Society
  34. 34. Proximity
  35. 35. Similarity
  36. 36. The law of good figure
  37. 37. Continuity
  38. 38. Closure
  39. 39. Emergence
  40. 40. Shape constancy or invariance
  41. 41. Analysis
  42. 42. Analyze these Dali images Salvador Dali: Mae West
  43. 43. Salvador Dali: Narcissus
  44. 44. Salvador Dali: The Phantom Cart
  45. 45. Salvador Dali: Galatea of Spheres
  46. 46. Depth Perception
  47. 47. Depth PerceptionD th P ti Monocular Binocular
  48. 48. Binocular
  49. 49. Photograph: Priyadarhsi Patnaik
  50. 50. Linear perspective Vanishing i t V i hi pointHorizon Road
  51. 51. Dali: Vertigo
  52. 52. Interposition
  53. 53. Relative SizeThe farther an object is from the eye, the smaller eyeit looksThe episode of the buffalos
  54. 54. Gustave Caillebotte: Paris
  55. 55. Size Constancy
  56. 56. Illusion roomSource: Blog site: MirageStudio7
  57. 57. Perceptual assumption Source: Encyclopedia Britannica Deluxe Edition 2007
  58. 58. Colour Perception
  59. 59. Source: Encyclopedia Britannica 2007 Deluxe Edition
  60. 60. Colour wheelWebsite of “The Joy of Perception”
  61. 61. Simultaneous ContrastWebsite of “The Joy of Perception”
  62. 62. Source: “Color in Mind: Adobe Magazine, November 1996
  63. 63. SizeSource: “Color in Mind: Adobe Magazine, November 1996
  64. 64. Brightness, colour and depth Website of “The Joy of Perception”
  65. 65. The light coloured dot seems to pop out while the dark coloured dot seems to sit further backSource: “Color in Mind: Adobe Magazine, November 1996
  66. 66. Analysis
  67. 67. Seurat: the Bathers
  68. 68. De Chirico: The Nostalgia of Infinite
  69. 69. Munch: The Scream
  70. 70. Francis Bacon: Crucifixion 3
  71. 71. Van Gogh: Cypress in Starry Night
  72. 72. Van Gogh: Wheatfield under threatening skies
  73. 73. Tibetan Buddhist Tanka painting
  74. 74. Colour symbolismCultural differencesAge differenceClass differenceCl diffGender differenceTrend or current fashion
  75. 75. IllusionThere is an innate ambiguity in retinal input. For a g y pgiven retinal image, there are infinite number of threedimensional images available for interpretation. Usuallywe get the interpretation right. When we don’t, we have t th i t rpr t ti ri ht Wh d ’t han illusion.Some illusions arise because there are more than onepossible interpretations.An illusion is a distortion of the senses, revealing howthe brain normally organizes and interprets sensorystimulation.
  76. 76. Types ofAmbiguous illusions are pictures or objects that g p jelicit a perceptual switch between the alternativeinterpretations.Distorting illusions are characterized by distortionsof size, length, or curvature.Paradox illusions are generated by objects that areparadoxical or impossible. d i l i iblFictional illusions (Hallucinations) are defined asthe perception of objects that are g p p bj genuinely not there yto all but a single observer, such as those induced byschizophrenia or a hallucinogen.
  77. 77. Image source: Encyclopedia Britannica 2007 deluxe edition
  78. 78. Image source: Encyclopedia Britannica 2007 deluxe edition
  79. 79. Image source:
  80. 80. Shape contrast: context Image source:
  81. 81. Simultaneous contrast/spreading Image source:
  82. 82. Image source:
  83. 83. Escher: Birds & fish
  84. 84. Escher on Escher"In the horizontal center strip there are birds and fish Inequivalent to each other. We associate flying with sky,and so for each of the black birds the sky in which it isflying is formed by the four white fish which encircle it.Similarly swimming makes us think of water, and watertherefore the four black birds that surround a fish becomethe water in which it swims." swims
  85. 85. Escher: Bond of union
  86. 86. Escher: Day & night
  87. 87. Escher: Mobius strip II
  88. 88. Magritte: Call of the Peaks
  89. 89. Magritte: the blank cheque
  90. 90. GiuseppeArcimboldo(1527-1593)(1527 1593)Italian Artist
  91. 91. Pieter Bruegel the Elder (1525-1559), Netherlands
  92. 92. Jos de Mey(1928 - 2007)Belgian Artist
  93. 93. Rob Gonsalves (1959-)Canadian Painter
  94. 94. Octavio Ocampo(1943-)Mexican Artist
  95. 95. Shigeo Fukuda(1932-2009)
  96. 96. References and images Doors of Perception The Joy of Perception Perception Online “Perception.” E l p di Britannica 2007 Deluxe Edition. “P ti ” Encyclopedia B it i D l Editi Art and Visual Perception. Rudolf Arnheim, University of California Press, 1984. Mark Hardin’s A hi ( M k H di ’ Artchive ( hi Colour. Bettey Edwards, Tarcher/Penguin, 2004. Perception, Gestalt, Panopticon, etc ( p p (Wikipedia) p )