1. 1 Sensation and Perception Chapter 6

2. 2 Sensation Sensing the World: Some Basic Principles  Thresholds  Sensory Adaptation

3. 3 Sensation Vision  The Stimulus Input: Light Energy  The Eye  Visual Information Processing  Color Vision

4. 4 Sensation The Other Senses  Hearing  Touch  Pain  Taste  Smell  Body Position and Movement

5. 5 Perception Perceptual Organization  Form Perception  Depth Perception  Perceptual Constancy

6. 6 Perception Perceptual Interpretation  Sensory Deprivation and Restored Vision  Perceptual Adaptation  Perceptual Set

7. 7 Sensation & Perception How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we select, organize, and interpret our sensations, the process is called perception.

8. 8 Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

9. 9 Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT

10. 10 Our sensory and perceptual processes work together to help us sort out complex images. Making Sense of Complexity “The Forest Has Eyes,” Bev Doolittle

11. 11 Sensing the World Senses are nature’s gift that suit an organism’s needs. A frog feeds on flying insects; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice.

12. 12 Exploring the Senses What stimuli cross our threshold for conscious awareness?

13. 13 Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World LightBrightness SoundVolume PressureWeight SugarSweet

14. 14 Thresholds Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time. Proportion of “Yes” Responses 0.00 0.50 1.00 0 5 10 15 20 25 Stimulus Intensity (lumens)

15. 15 Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock

16. 16 Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k =  I/I. StimulusConstant (k) Light8% Weight2% Tone3%

17. 17 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it.

18. 18 Now you see, now you don’t

19. 19 Vision

20. 20 Transduction In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses.

21. 21 Visible Spectrum The Stimulus Input: Light Energy Both Photos: Thomas Eisner

22. 22 Physical Characteristics of Light 1.Wavelength (hue/color) 2.Intensity (brightness)

23. 23 Wavelength (Hue) Hue (color) is the dimension of color determined by the wavelength of the light. Wavelength is the distance from the peak of one wave to the peak of the next.

24. 24 Wavelength (Hue) Different wavelengths of light result in different colors. 400 nm 700 nm Long wavelengths Short wavelengths Violet IndigoBlue Green Yellow OrangeRed

25. 25 Intensity (Brightness) Intensity: Amount of energy in a wave determined by the amplitude. It is related to perceived brightness.

26. 26 Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more “washed out” or “darkened.”

27. 27 The Eye

28. 28 Parts of the eye 1.Cornea: Transparent tissue where light enters the eye. 2.Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. 3.Lens: Focuses the light rays on the retina. 4.Retina: Contains sensory receptors that process visual information and sends it to the brain.

29. 29 The Lens Lens: Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

30. 30 Retina Retina: The light- sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information.

31. 31 Optic Nerve, Blind Spot & Fovea http://www.bergen.org Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster.

32. 32 Test your Blind Spot Use your textbook. Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At some point the car on the right will disappear due to a blind spot.

33. 33 Photoreceptors E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

34. 34 Bipolar & Ganglion Cells Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which converge to form the optic nerve.

35. 35 Visual Information Processing Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.

36. 36 Feature Detection Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. Ross Kinnaird/ Allsport/ Getty Images

37. 37 Shape Detection Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses. Ishai, Ungerleider, Martin and Haxby/ NIMH

38. 38 Visual Information Processing Processing of several aspects of the stimulus simultaneously is called parallel processing. The brain divides a visual scene into subdivisions such as color, depth, form, movement, etc.

39. 39 From Sensation to Recognition Tim Bieber/ The Image Bank

40. 40 Color Vision Trichromatic theory: Young and von Helmholtz suggested that the eye must contain three receptors that are sensitive to red, blue and green colors. Blue Green Red Medium Low Max Standard stimulus Comparison stimulus

41. 41 Color Blindness Ishihara Test Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory.

42. 42 Opponent Colors Gaze at the middle of the flag for about 30 Seconds. When it disappears, stare at the dot and report whether or not you see Britain's flag.

43. 43 The Other Senses

44. 44 Hearing The Stimulus Input: Sound Waves Sound waves are compressing and expanding air molecules.

45. 45 Sound Characteristics 1.Frequency (pitch) 2.Intensity (loudness)

46. 46 Frequency (Pitch) Frequency (pitch): The dimension of frequency determined by the wavelength of sound. Wavelength: The distance from the peak of one wave to the peak of the next.

47. 47 Intensity (Loudness) Intensity (Loudness): Amount of energy in a wave, determined by the amplitude, relates to the perceived loudness.

48. 48 Loudness of Sound 70dB 120dB Richard Kaylin/ Stone/ Getty Images

49. 49 The Ear Dr. Fred Hossler/ Visuals Unlimited

50. 50 The Ear Outer Ear: Collects and sends sounds to the eardrum. Middle Ear: Chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window. Inner Ear: Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.

51. 51 Cochlea Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals.

52. 52 Localization of Sounds Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound.

53. 53 Localization of Sound 1. Intensity differences 2. Time differences Time differences as small as 1/100,000 of a second can cause us to localize sound. The head acts as a “shadow” or partial sound barrier.

54. 54 Touch The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain. Bruce Ayers/ Stone/ Getty Images

55. 55 Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. Burning hot PressureVibration Cold, warmth and pain

56. 56 Pain Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in which the afflicted person feels no pain. Ashley Blocker (right) feels neither pain nor extreme hot or cold. AP Photo/ Stephen Morton

57. 57 Biopsychosocial Influences

58. 58 Gate-Control Theory Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gary Comer/ PhototakeUSA.com

59. 59 Pain Control Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction. Todd Richards and Aric Vills, U.W. ©Hunter Hoffman, www.vrpain.com

60. 60 Taste Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”. Sweet Sour Salty BitterUmami (Fresh Chicken)

61. 61 Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor.

62. 62 Smell Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell.

63. 63 Smell and Memories The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell.

64. 64 Body Position and Movement The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position. http://www.heyokamagazine.com Whirling Dervishes Wire Walk Bob Daemmrich/ The Image Works

65. 65 Perceptual Organization How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that a figure formed a “whole” different than its surroundings.

66. 66 Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Form Perception Time Savings Suggestion, © 2003 Roger Sheperd.

67. 67 Grouping After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules.

68. 68 Grouping & Reality Although grouping principles usually help us construct reality, they may occasionally lead us astray. Both photos by Walter Wick. Reprinted from GAMES Magazine..© 1983 PCS Games Limited Partnership

69. 69 Depth Perception Visual Cliff Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. Innervisions

70. 70 Binocular Cues Retinal disparity: Images from the two eyes differ. Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset.

71. 71 Monocular Cues Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

72. 72 Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer. Rene Magritte, The Blank Signature, oil on canvas, National Gallery of Art, Washington. Collection of Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli.

73. 73 Monocular Cues Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower. Image courtesy of Shaun P. Vecera, Ph. D., adapted from stimuli that appered in Vecrera et al., 2002

74. 74 Monocular Cues Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

75. 75 Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. © The New Yorker Collection, 2002, Jack Ziegler from cartoonbank.com. All rights reserved.

76. 76 Monocular Cues Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away. From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved.

77. 77 Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal images change.

78. 78 Perceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object. Color Constancy

79. 79 Size-Distance Relationship The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues. From Shepard, 1990 Alan Choisnet/ The Image Bank

80. 80 Size-Distance Relationship Both girls in the room are of similar height. However, we perceive them to be of different heights as they stand in the two corners of the room. Both photos from S. Schwartzenberg/ The Exploratorium

81. 81 Ames Room The Ames room is designed to demonstrate the size- distance illusion.

82. 82 Lightness Constancy The color and brightness of square A and B are the same. Courtesy Edward Adelson

83. 83 Perceptual Interpretation Immanuel Kant (1724-1804) maintained that knowledge comes from our inborn ways of organizing sensory experiences. John Locke (1632-1704) argued that we learn to perceive the world through our experiences. How important is experience in shaping our perceptual interpretation?

84. 84 Sensory Deprivation & Restored Vision After cataract surgery, blind adults were able to regain sight. These individuals could differentiate figure and ground relationships, yet they had difficulty distinguishing a circle and a triangle (Von Senden, 1932).

85. 85 Facial Recognition After blind adults regained sight, they were able to recognize distinct features, but were unable to recognize faces. Normal observers also show difficulty in facial recognition when the lower half of the pictures are changed. Courtesy of Richard LeGrand

86. 86 Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars. Blakemore & Cooper (1970) Sensory Deprivation

87. 87 Perceptual Adaptation Visual ability to adjust to an artificially displaced visual field, e.g., prism glasses. Courtesy of Hubert Dolezal

88. 88 Perceptual Set A mental predisposition to perceive one thing and not another. What you see in the center picture is influenced by flanking pictures. From Shepard, 1990.

89. 89 (a) Loch ness monster or a tree trunk; (b) Flying saucers or clouds? Perceptual Set Other examples of perceptual set. Frank Searle, photo Adams/ Corbis-Sygma Dick Ruhl

90. 90 Is the “magician cabinet” on the floor or hanging from the ceiling? Context Effects Context can radically alter perception.

91. 91 To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree. Cultural Context Context instilled by culture also alters perception.

92. 92 Perception Revisited Is perception innate or acquired?

93. 93 Is There Extrasensory Perception? Perception without sensory input is called extrasensory perception (ESP). A large percentage of scientists do not believe in ESP.

94. 94 Claims of ESP 1.Telepathy: Mind-to-mind communication. One person sending thoughts and the other receiving them. 2.Clairvoyance: Perception of remote events, such as sensing a friend’s house on fire. 3.Precognition: Perceiving future events, such as a political leader’s death.