1. Chapter Three Sensation and Perception

2. Copyright © Houghton Mifflin Company. All rights reserved. 3-2 Did You Know That… Our sense of smell may not be as keen as that of dogs, but humans can detect the presence of even one drop of perfume dispersed through a small house? Roy G. Biv is one of the most famous names learned by psychology students, but he is not a real person? Listening to music with headphones or similar device can permanently damage your hearing?

3. Copyright © Houghton Mifflin Company. All rights reserved. 3-3 Did You Know That… (Cont’d) Salmon use the sense of smell to sniff out the streams of their birth when they return to spawn? Some people are born with a distaste for broccoli? We have a sense that enables us to locate the parts of our body in the dark?

4. Copyright © Houghton Mifflin Company. All rights reserved. 3-4 Did You Know That… (Cont’d) Newborn babies prefer the sounds of their mothers’ voices to the voices of other women? The mechanism that makes motion pictures possible lies in the viewer, not the projector?

5. Module 3.1 Sensing Our World: Basic Concepts of Sensation

6. Copyright © Houghton Mifflin Company. All rights reserved. 3-6 Module 3.1 Preview Questions What is sensation? What is the difference between absolute thresholds and difference thresholds? What factors contribute to signal detection? What is sensory adaptation?

7. Copyright © Houghton Mifflin Company. All rights reserved. 3-7 What Is Sensation? The process by which we receive, transform, and process stimuli into neural impulses The brain uses these impulses to create experiences of vision, touch, hearing, taste, smell, etc.

8. Copyright © Houghton Mifflin Company. All rights reserved. 3-8 Sensory Receptors Specialized cells that detect sensory stimuli and convert them into neural impulses Locations of sensory receptors: Eyes Ears Nose Mouth Joints, muscles Skin

9. Copyright © Houghton Mifflin Company. All rights reserved. 3-9 Psychophysics The study of how physical sources of stimulation relate to the experience of these stimuli in the form of sensations Began with the work of 19th century German scientist Gustav Theodor Fechner

10. Copyright © Houghton Mifflin Company. All rights reserved. 3-10 Absolute and Difference Thresholds Absolute Threshold: Smallest amount of a stimulus that a person can reliably detect Absolute thresholds for different senses Difference threshold: The minimal difference between two stimuli that people can reliably detect Also called “just-noticeable difference” Weber’s law

11. Copyright © Houghton Mifflin Company. All rights reserved. 3-11 Table 3.1: Absolute Thresholds for Various Senses Return

12. Copyright © Houghton Mifflin Company. All rights reserved. 3-12 Table 3.2: Examples of Weber’s Constants

13. Copyright © Houghton Mifflin Company. All rights reserved. 3-13 Signal Detection Theory The theory that the threshold for detecting a signal depends on: The intensity of the stimulus The level of background stimulation The biological and psychological characteristics of the perceiver

14. Copyright © Houghton Mifflin Company. All rights reserved. 3-14 Sensory Adaptation The process by which sensory receptors become less sensitive to constant or unchanging stimuli May not occur when repeatedly exposed to certain strong stimuli

15. Module 3.2 Vision: Seeing the Light

16. Copyright © Houghton Mifflin Company. All rights reserved. 3-16 Module 3.2 Preview Questions How do the eyes process light? What are feature detectors, and what role do they play in visual processing? What are the two major theories of color vision? What are the two major forms of color blindness?

17. Copyright © Houghton Mifflin Company. All rights reserved. 3-17 Figure 3.1: The Electromagnetic Spectrum

18. Copyright © Houghton Mifflin Company. All rights reserved. 3-18 Figure 3.2: The Color Spectrum

19. Copyright © Houghton Mifflin Company. All rights reserved. 3-19 Figure 3.3: Parts of the Eye

20. Copyright © Houghton Mifflin Company. All rights reserved. 3-20 Photoreceptors The retina contains specialized receptor cells that are sensitive to light. Two types of photoreceptors: Rods: Allows detection of objects in low light; also responsible for peripheral vision Cones: Allows detection of color as well as fine details of objects in bright light

21. Copyright © Houghton Mifflin Company. All rights reserved. 3-21 Figure 3.5: Conversion of Light to Neural Impulses

22. Copyright © Houghton Mifflin Company. All rights reserved. 3-22 Visual Acuity The ability to discern visual details. Nearsighted if need to be unusually close to discern an object’s details Eyeball is too long or the cornea is too curved. Farsighted if need to be unusually far away from objects to see them clearly Eyeball is too short.

23. Copyright © Houghton Mifflin Company. All rights reserved. 3-23 Feature Detectors Neurons that respond to specific features of the visual stimulus Visual cortex compiles information from various cells to form meaningful patterns

24. Copyright © Houghton Mifflin Company. All rights reserved. 3-24 Trichromatic Theory of Color Vision Thomas Young (1773-1829) Hermann von Helmholtz (1821- 1894) Eyes have 3 types of color receptors or “cones.” Red, green, blue-violet Figure 3.7: Primary Colors

25. Copyright © Houghton Mifflin Company. All rights reserved. 3-25 Figure 3.8: Primary Colors

26. Copyright © Houghton Mifflin Company. All rights reserved. 3-26 Unnumbered Figure 3.1

27. Copyright © Houghton Mifflin Company. All rights reserved. 3-27 Opponent-Process Theory Ewald Hering (1834-1918) Three pairs of opposing color receptors Red-Green Blue-Yellow Black-White When one color is activated, other is inhibited.

28. Copyright © Houghton Mifflin Company. All rights reserved. 3-28 Which Theory of Color Vision Is Correct? Both theories, to a certain extent Trichromatic theory is correct at the receptor level. Opponent-process is correct with respect to behavior of cells that lie between the cones and the occipital lobe.

29. Copyright © Houghton Mifflin Company. All rights reserved. 3-29 Figure 3.9: Color Blindness Trichromats: Normal color vision Monochromats: No color vision Dichromats: Can see some colors but not others

30. Module 3.3 Hearing: The Music of Sound

31. Copyright © Houghton Mifflin Company. All rights reserved. 3-31 Module 3.3 Preview Questions How does the ear enable us to hear sound? What determines our perception of pitch? What are the main types and causes of deafness?

32. Copyright © Houghton Mifflin Company. All rights reserved. 3-32 Figure 3.10: Sound Waves

33. Copyright © Houghton Mifflin Company. All rights reserved. 3-33 Characteristics of Sound Amplitude determines perceived loudness. Measured in decibels (dB) Frequency determines perceived pitch. How high or low a sound seems

34. Copyright © Houghton Mifflin Company. All rights reserved. 3-34 Figure 3.11: Conversion of Sound Waves into Neural Impulses

35. Copyright © Houghton Mifflin Company. All rights reserved. 3-35 Perception of Pitch Place Theory: Location of vibration along basilar membrane determines pitch. Explains pitch of high-frequency sounds Frequency Theory: Basilar membrane vibrates at same frequency as sound wave. Explains pitch of low-frequency sounds Volley Principle: Groups of neurons along basilar membrane fire in rotation. Suggests how perceive mid-range sounds

36. Copyright © Houghton Mifflin Company. All rights reserved. 3-36 Figure 3.12: Sounds and Decibels

37. Copyright © Houghton Mifflin Company. All rights reserved. 3-37 Hearing Loss Conduction Deafness: Damage to middle ear May benefit from hearing aids Nerve Deafness: Damage to hair cells of the inner ear or auditory nerve Use of cochlear implants sometimes successful Hearing loss is not inevitable.

38. Module 3.4 Our Other Senses: Chemical, Skin, and Body Senses

39. Copyright © Houghton Mifflin Company. All rights reserved. 3-39 Module 3.4 Preview Questions How do we sense odors and tastes? What are the skin senses? What are the kinesthetic and vestibular senses?

40. Copyright © Houghton Mifflin Company. All rights reserved. 3-40 Olfaction Our sense of smell Stimulation depends on the shape of the molecules of chemical substances. Capable of sensing about 10,000 different substances Only sense that does not pass through the thalamus.

41. Copyright © Houghton Mifflin Company. All rights reserved. 3-41 Figure 3.13: Olfaction

42. Copyright © Houghton Mifflin Company. All rights reserved. 3-42 Pheromones Chemical substances emitted by many species Found in bodily secretions Detected by other members of the species through the sense of smell or taste Plays important roles in many behaviors, including sexual attraction Do pheromones influence human behaviors?

43. Copyright © Houghton Mifflin Company. All rights reserved. 3-43 Taste Four basic tastes: sweet, sour, salty, bitter Flavor derives from: taste, aroma, texture, temperature

44. Copyright © Houghton Mifflin Company. All rights reserved. 3-44 Factors Influencing Food Preference Cultural background Genetic factors Taste sensitivity One in 4 are “supertasters” Gender and ethnic or racial differences in taste sensitivity

45. Copyright © Houghton Mifflin Company. All rights reserved. 3-45 The Skin Senses Largest sensory organ Codes for sensations of touch, pressure, warmth, cold, and pain Pain is adaptive. Figure 3.14

46. Copyright © Houghton Mifflin Company. All rights reserved. 3-46 Gate-Control Theory Of Pain A gating mechanism in the spinal cord controls pain messages. Bottleneck at the “gate” may block pain. Role of endorphins in controlling pain Release of endorphins may explain benefits of acupuncture.

47. Copyright © Houghton Mifflin Company. All rights reserved. 3-47 Kinesthesis Body sense that provides information about: Movement of body parts Relative position of body parts Receptors located in joints, ligaments, and muscles

48. Copyright © Houghton Mifflin Company. All rights reserved. 3-48 Vestibular Sense Functions: Monitors position of body in space Helps maintain balance Monitors position of head Conflict with vision = motion sickness Continue

49. Copyright © Houghton Mifflin Company. All rights reserved. 3-49 Figure 3.15: Vestibular Sense Return

50. Module 3.5 Perceiving Our World: Principles of Perception

51. Copyright © Houghton Mifflin Company. All rights reserved. 3-51 Module 3.5 Preview Questions What is perception? How is perception influenced by attention and perceptual set? What are the two general modes of processing visual stimuli? What are the Gestalt principles of perceptual organization?

52. Copyright © Houghton Mifflin Company. All rights reserved. 3-52 Module 3.5 Preview Questions (Cont’d) What is perceptual constancy, and what cues do we use to perceive depth and movement? What are visual illusions? Does subliminal perception exist? Does evidence support the existence of ESP?

53. Copyright © Houghton Mifflin Company. All rights reserved. 3-53 Perception The process by which the brain interprets sensations Turns them into meaningful representations of the world Perception is an active process. Perceptions may not accurately reflect external reality.

54. Copyright © Houghton Mifflin Company. All rights reserved. 3-54 Figure 3.16: Perception vs. Reality?

55. Copyright © Houghton Mifflin Company. All rights reserved. 3-55 Attention First step in perception: Role of selective attention Influenced by: Motivational states Repeated exposure Constant exposure can lead to habituation.

56. Copyright © Houghton Mifflin Company. All rights reserved. 3-56 Figure 3.17: What Do You See Here? Perceptions are influenced by our expectations or preconceptions. Is this the Letter B or the Number 13?

57. Copyright © Houghton Mifflin Company. All rights reserved. 3-57 Visual Processing Bottom-Up Processing: Focus on specific shapes, individual features Brain assembles specific features of shapes to form patterns. Patterns are compared with stored images. Top-Down Processing: Experience and knowledge shape perception Recognize patterns as meaningful wholes

58. Copyright © Houghton Mifflin Company. All rights reserved. 3-58 Figure 3.18: A Duck or a Rabbit? From Sensation and Perception: An Integrated Approach, From H.R. Schiffman. Copyright © 2000 by John Wiley & Sons Inc., This material is used with permission of John Wiley & Sons Inc.

59. Copyright © Houghton Mifflin Company. All rights reserved. 3-59 Laws of Perceptual Organization Figure and Ground Reversible figure Ambiguous figure Gestalt Laws of Grouping

60. Copyright © Houghton Mifflin Company. All rights reserved. 3-60 Figure 3.20: Reversible Figure Return Is this a vase or a profile of two faces?

61. Copyright © Houghton Mifflin Company. All rights reserved. 3-61 Figure 3.21: Ambiguous Figure Do you see an old woman or a young one?

62. Copyright © Houghton Mifflin Company. All rights reserved. 3-62 Figure 3.23: Old/Young Woman Return

63. Copyright © Houghton Mifflin Company. All rights reserved. 3-63 Figure 3.23: Gestalt Laws of Grouping

64. Copyright © Houghton Mifflin Company. All rights reserved. 3-64 Perceptual Constancies Tendency to perceive an object as remaining the same even when retinal image changes Examples: Shape constancy Size constancy Color constancy Brightness constancy Continue

65. Copyright © Houghton Mifflin Company. All rights reserved. 3-65 Figure 3.24: Shape Constancy Return

66. Copyright © Houghton Mifflin Company. All rights reserved. 3-66 Binocular Cues for Depth Perception Cues that involve both eyes Retinal Disparity: Cue for distance based on the slight differences in the visual impressions formed in both eyes Convergence: Cue for distance based on the degree of tension required to focus two eyes on the same object

67. Copyright © Houghton Mifflin Company. All rights reserved. 3-67 Monocular Cues for Depth Perception Cues that depend on one eye only Examples of cues: Relative size Interposition Relative clarity Texture gradient Linear perspective Shadowing

68. Copyright © Houghton Mifflin Company. All rights reserved. 3-68 Cues for Motion Perception Path of image as it crosses the retina The changing size of the object

69. Copyright © Houghton Mifflin Company. All rights reserved. 3-69 Visual Illusions: Do Your Eyes Deceive You? Müller-Lyer illusion and the Ponzo illusion Impossible figures Moon illusion Relative-size hypothesis as a possible explanation. Stroboscopic movement

70. Copyright © Houghton Mifflin Company. All rights reserved. 3-70 Figure 3.27: Müller-Lyer Illusion and Ponzo Illusion Return

71. Copyright © Houghton Mifflin Company. All rights reserved. 3-71 Figure 3.28: Impossible Figure Return

72. Copyright © Houghton Mifflin Company. All rights reserved. 3-72 Cultural Differences Perception influenced by both sensory systems as well as cultural experiences Müller-Lyer illusion and the carpentered- world hypothesis Ponzo illusion less prominent among people of Guam

73. Copyright © Houghton Mifflin Company. All rights reserved. 3-73 Subliminal Perception Stimuli presented below level of conscious awareness Does subliminal perception exist? A qualified yes Effects appear to be subtle and depend on very precise experimental conditions. Can it influence attitudes or behavior? No convincing evidence exists that it can.

74. Copyright © Houghton Mifflin Company. All rights reserved. 3-74 Extrasensory Perception Perception that occurs without benefit of the known senses Common forms of paranormal phenomena identified with ESP: Telepathy Clairvoyance Precognition Psychokinesis Has not been demonstrated scientifically

75. Application Module 3.6 Psychology and Pain Management

76. Copyright © Houghton Mifflin Company. All rights reserved. 3-76 Module 3.6 Preview Question What have psychologists learned about controlling pain?

77. Copyright © Houghton Mifflin Company. All rights reserved. 3-77 Pain Management Distraction Creating a bottleneck at the “gate” Changing thoughts and attitudes Obtaining accurate information Meditation Biofeedback