1. Chapter 3 Sensation and Perception

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

3. 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?

4. 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.

5. Perception  A process that makes sensory patterns meaningful and more elaborate Draws heavily on memory, motivation, emotion, & other psychological processes Draws heavily on memory, motivation, emotion, & other psychological processes  The selection, organization, and interpretation of sensory input involving organizing and translating sensory input into meaningful patterns The sense organs convert stimulation into neural impulses that are understood by the brain The sense organs convert stimulation into neural impulses that are understood by the brain

6. Sensation vs. Perception  Normally processes of sensation and perception are difficult to separate  Automatically organize incoming sensory stimulation as soon as it arrives

7. Sensory Receptors  Specialized cells that detect sensory stimuli and convert them into neural impulses  Locations of sensory receptors: Eyes Eyes Ears Ears Nose Nose Mouth Mouth Joints, muscles Joints, muscles Skin Skin

8. 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

9. Absolute and Difference Thresholds: Is Something There? Is Something ELSE there?  Absolute Threshold: smallest amount of a stimulus that a person can reliably detect Absolute thresholds for different senses Absolute thresholds for different senses Absolute thresholds for different senses Absolute thresholds for different senses  Difference threshold: the minimal difference between two stimuli that people can reliably detect Also called “just-noticeable difference” Also called “just-noticeable difference” Weber’s law Weber’s law Weber’s law Weber’s law Continue

10. Signal Detection: More than a Matter of Energy  The theory that the threshold for detecting a signal depends on: The intensity of the stimulus The intensity of the stimulus The level of background stimulation The level of background stimulation The biological and psychological characteristics of the perceiver The biological and psychological characteristics of the perceiver

11. Sensory Adaptation: Turning the Volume Down  The process by which sensory receptors become less sensitive to constant or unchanging stimuli  May not occur when repeatedly exposed to certain strong stimuli

12. Module 3.2 Vision: Seeing the Light

13. 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?

14. 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 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 Cones: allows detection of color as well as fine details of objects in bright light

15. 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 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 Eyeball is too short

16. Feature Detectors: Getting Down to Basics  Neurons that respond to specific features of the visual stimulus such as horizontal or vertical lines  Visual cortex compiles information from various cells to form meaningful patterns

17. Opponent-Process Theory  Ewald Hering (1834–1918)  Three pairs of opposing color receptors Red-Green Red-Green Blue-Yellow Blue-Yellow Black-White Black-White  When one color is activated, other is inhibited.

18. Which Theory of Color Vision Is Correct?  Both theories are correct, 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.

19. Module 3.3 Hearing: The Music of Sound

20. 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?

21. Characteristics of Sound  Amplitude determines perceived loudness. Measured in decibels (dB) Measured in decibels (dB)  Frequency determines perceived pitch How high or low a sound seems How high or low a sound seems

22. Perception of Pitch  Place Theory  Frequency Theory  Volley Principle

23. Hearing Loss: Are You Protecting Your Hearing?  Conduction Deafness: damage to middle ear May benefit from hearing aids May benefit from hearing aids  Nerve Deafness: damage to hair cells of the inner ear or auditory nerve Use of cochlear implants sometimes successful Use of cochlear implants sometimes successful  Hearing loss is not inevitable.

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

25. Module 3.4 Preview Questions  How do we sense odors?  How do we sense tastes?  What are the skin senses?  What are the kinesthetic and vestibular senses?

26. Olfaction: What Your Nose Knows  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, goes directly to the olfactory bulb

27. The Gustatory System  Gustatory receptors are cluster of taste cells found in the taste buds  Taste buds only last about 10 days

28. Gate-Control Theory of Pain  A gating mechanism in the spinal cord controls pain messages Bottleneck at the “gate” may block pain Bottleneck at the “gate” may block pain  Role of endorphins in controlling pain Release of endorphins may explain benefits of acupuncture Release of endorphins may explain benefits of acupuncture

29. Kinesthesis  Body sense that provides information about: Movement of body parts Movement of body parts Relative position of body parts Relative position of body parts  Receptors located in joints, ligaments, and muscles

30. Vestibular Sense  Functions: Monitors position of body in space Monitors position of body in space Helps maintain balance Helps maintain balance  Monitors position of head Monitors position of head Monitors position of head  Conflict with vision = motion sickness Continue

31. Module 3.5 Perceiving Our World: Principles of Perception

32. Module 3.5 Preview Questions  How is perception influenced by attention?  How is perception influenced by perceptual set?  What are the two general modes of processing visual stimuli?  What are the Gestalt principles of perceptual organization?

33. Module 3.5 Preview Questions (Cont’d)  What is perceptual constancy?  What cues do we use to perceive depth?  What cues do we use to perceive movement?  What are visual illusions?  Does subliminal perception exist?  Does evidence support the existence of ESP?

34. Perception  The process by which the brain interprets sensations Turns them into meaningful representations of the world Turns them into meaningful representations of the world  Perception is an active process  Perceptions may not accurately reflect external reality

35. Attention: Did You Notice That?  First step in perception: Role of selective attention Role of selective attention  Influenced by: Motivational states Motivational states Repeated exposure Repeated exposure  Constant exposure can lead to habituation.

36. Example: Word strings

37. Modes of Visual Processing  Bottom-Up Processing: focus on specific shapes, individual features Brain assembles specific features of shapes to form patterns Brain assembles specific features of shapes to form patterns Patterns are compared with stored images Patterns are compared with stored images  Top-Down Processing: experience and knowledge shape perception Recognize patterns as meaningful wholes Recognize patterns as meaningful wholes

38. Principles of Visual System Organization  Figure & ground  Filling in the blanks Subjective contours Subjective contours Closure Closure  Laws of perceptual grouping Law of similarity Law of similarity Law of proximity Law of proximity Law of continuity Law of continuity Law of common fate Law of common fate  Law of Prägnanz

39. Principles of Visual System Organization  Figure & ground  Filling in the blanks Subjective contours Subjective contours Closure Closure  Laws of perceptual grouping Law of similarity Law of similarity Law of proximity Law of proximity Law of continuity Law of continuity Law of common fate Law of common fate  Law of Prägnanz

40. Filling in the Blanks  Subjective contours- boundaries that are perceived but do not appear in a stimulus pattern  No lines separating triangle from white background of screen

41. Closure  Identifies the tendency to fill in gaps in figures & to see incomplete figures as complete  Can you identify this picture ?

42. Law of similarity  Tend to group similar objects together in our perceptions

43. Law of Proximity  Things that are near one another seem to belong together

44. Law of Common Fate  Tend to group similar objects together that share a common motion or destination  When dots 1, 3, and 5 move up and dots 2, 4, and 6, move down at the same time, the dots moving in the same direction are perceived as a group (see example)  http://coe.sdsu.edu/eet/articles/visualperc1 /start.htm http://coe.sdsu.edu/eet/articles/visualperc1 /start.htm http://coe.sdsu.edu/eet/articles/visualperc1 /start.htm

45. Law of Prägnanz  The simplest organization, requiring the least cognitive effort, will emerge as the figure (why proofreading hard)  Figure appears as square overlapping triangle, not a combination of several complicated shapes

46. Perceptual Constancies  Tendency to perceive an object as remaining the same even when retinal image changes  Examples: Shape constancy Shape constancy Shape constancy Shape constancy Size constancy Size constancy Color constancy Color constancy Brightness constancy Brightness constancy Continue

47. 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

48. Monocular Cues for Depth Perception  Cues that depend on one eye only  Examples of cues: Relative size Relative size Interposition Interposition Relative clarity Relative clarity Texture gradient Texture gradient Linear perspective Linear perspective Shadowing Shadowing

49. Cues for Motion Perception  Path of image as it crosses the retina  The changing size of the object

50. Visual Illusions: Do Your Eyes Deceive You?  Müller-Lyer illusion and the Ponzo illusion Müller-Lyer illusion and the Ponzo illusion Müller-Lyer illusion and the Ponzo illusion  Impossible figures Impossible figures Impossible figures  Moon illusion Relative-size hypothesis as a possible explanation Relative-size hypothesis as a possible explanation  Stroboscopic movement Continue

51. Impossible Figures Figures that can be represented in two- dimensional pictures but cannot exist in three-dimensionalspace

52. Impossible Staircase  http://www.moillusions.com/2007/04/ascen ding-ball-staircase-illusion.html http://www.moillusions.com/2007/04/ascen ding-ball-staircase-illusion.html http://www.moillusions.com/2007/04/ascen ding-ball-staircase-illusion.html

53. Cultural Differences in Perceiving Visual Illusions  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

54. Subliminal Perception  Stimuli presented below level of conscious awareness  Does subliminal perception exist? A qualified yes A qualified yes Effects appear to be subtle and depend on very precise experimental conditions 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 No convincing evidence exists that it can

55. Extrasensory Perception (ESP)  Perception that occurs without benefit of the known senses  Common forms of paranormal phenomena identified with ESP: Telepathy Telepathy Clairvoyance Clairvoyance Precognition Precognition Psychokinesis Psychokinesis  Has not been demonstrated scientifically

56. Application Module 3.6 Psychology and Pain Management

57. Pain Management  Distraction  Creating a bottleneck at the “gate”  Changing thoughts and attitudes  Obtaining accurate information  Meditation  Biofeedback