1. Myers’ PSYCHOLOGY (6th Ed) Chapter 5 Sensation James A. McCubbin, PhD Clemson University Worth Publishers

2. Sensation  Sensation  a process by which our sensory receptors and nervous system receive and represent stimulus energy  Perception  a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

3. Sensation  Our sensory and perceptual processes work together to help us sort out complex processes

4. Sensation  Bottom-Up Processing  analysis that begins with the sense receptors and works up to the brain’s integration of sensory information  Top-Down Processing  information processing guided by higher-level mental processes  as when we construct perceptions drawing on our experience and expectations

5. Making sense of the world What am I seeing? Is that something I’ve seen before? Bottom-up processing: taking sensory information and then assembling and integrating it Top-down processing: using models, ideas, and expectations to interpret sensory information 5

6. Do you see a painting or a 3D bottle? What’s on the bottle? Kids see eight to ten dolphins. Why do you think kids see something different from what adults see? 6

7. Top-down Processing You may start to see something in this picture if we give your brain some concepts to apply: “tree” “sidewalk” “dog” “Dalmatian” 7

8. From Sensory Organs to the Brain The process of sensation can be seen as three steps: Reception-- the stimulation of sensory receptor cells by energy (sound, light, heat, etc) Transduction-- transforming this cell stimulation into neural impulses Transmission-- delivering this neural information to the brain to be processed 8

9. Sensation- Basic Principles  Psychophysics  study of the relationship between physical characteristics of stimuli and our psychological experience of them  Light - brightness  Sound - volume  Pressure - weight  Taste - sweetness

10. Sensation- Thresholds  Absolute Threshold  minimum stimulation needed to detect a particular stimulus 50% of the time  Difference Threshold  minimum difference between two stimuli required for detection 50% of the time  just noticeable difference (JND)

11. Sensation- Thresholds  Signal Detection Theory  predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)  assumes that there is no single absolute threshold  detection depends partly on person’s  experience  expectations  motivation  level of fatigue

12. Sensation- Thresholds  Subliminal  When stimuli are below one’s absolute threshold for conscious awareness 0 25 50 75 100 LowAbsolute threshold Medium Intensity of stimulus Percentage of correct detections Subliminal stimuli

13. Subliminal Stimulation  Priming—The activation, often unconsciously, of certain associations, thus pre-disposing one’s perception, memory, or response.  “masking” stimulus that interrupts the brain’s processing  Ex. Back-masking of music  http://jeffmilner.com/backmasking/

14. Sensation- Thresholds  Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage  light intensity- 8%  weight- 2%  tone frequency- 0.3%  Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

15.  To detect novelty in our surroundings, our senses tune out a constant stimulus.  The rock in your shoe or the ticking of a clock are more difficult to sense after a while.  We don’t notice this visually because normally our eyes are constantly moving.  However, if you concentrate on keeping your eyes in one spot, you’ll see the effects, as your eyes adjust to stimuli in the following slides. Sensory Adaptation 15

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17. Sensory Adaptation Sensory adaptation- diminished sensitivity as a consequence of constant stimulation *try it: move your watch up your wrist an inch… *try it: try working in a noisy cafe *try it: fart in a car, and after the smell has disappeared, invite a friend to join you. Now, consider, why do our senses diminish in their sensitivity? (Informative changes in environment)

18. Vision- Stabilized Images on the Retina

19. Vision  Transduction  conversion of one form of energy to another  in sensation, transforming of stimulus energies into neural impulses  Wavelength  the distance from the peak of one wave to the peak of the next

20. Vision  Hue  dimension of color determined by wavelength of light  Intensity  amount of energy in a wave determined by amplitude  brightness  loudness

21. The spectrum of electromagnetic energy

22. Vision- Physical Properties of Waves Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Great amplitude (bright colors, loud sounds) Small amplitude (dull colors, soft sounds)

23. Vision  Pupil- adjustable opening in the center of the eye  Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening  Lens- transparent structure behind pupil that changes shape to focus images on the retina

24. Vision

26.  Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina  Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

27. Vision  Acuity- the sharpness of vision  Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina  Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

28. Vision Farsighted Nearsighted Normal Vision Vision Vision

29. Retina’s Reaction to Light- Receptors  Rods  peripheral retina  detect black, white and gray  twilight or low light  Cones  near center of retina  fine detail and color vision  daylight or well-lit conditions

30. Retina’s Reaction to Light  Optic nerve- nerve that carries neural impulses from the eye to the brain  Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there  Fovea- central point in the retina, around which the eye’s cones cluster

32. Rods and Cones

33. Vision- Receptors Receptors in the Human Eye ConesRods Number Location in retina Sensitivity in dim light Color sensitive?Yes Low Center 6 million No High Periphery 120 million

34. Pathways from the Eyes to the Visual Cortex

35. Visual Information Processing  Feature Detectors  nerve cells in the brain that respond to specific features  shape  angle  movement Stimulus Cell’s responses

36. Visual Information Processing o The motion aftereffect (MAE) is a visual illusion experienced after viewing a moving visual stimulus for a time (tens of milliseconds to minutes) with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original (physically moving) stimulus. The motion aftereffect is believed to be the result of motion adaptation.visual illusionstimulusmotionadaptation o Neurons coding a particular movement reduce their responses with time of exposure to a constantly moving stimulus; this is neural adaptation Neuronsneural adaptation

38. How the Brain Perceives

39. Illusory Contours

40. Visual Information Processing  Parallel Processing  simultaneous processing of several aspects of a problem simultaneously  The brain’s natural mode of information processing for many functions, including vision. Contrasts with step-by-step processing (serial) processing of most computers and of conscious problem solving.

42. Visual Information Processing  Trichromatic (three color) Theory  Young and Helmholtz  three different retinal color receptors  red  green  blue

43. Color-Deficient Vision  People who suffer red-green blindness have trouble perceiving the number within the design

44. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON”“OFF” red green green red blue yellow yellow blue black white white black

45. Opponent Process- Afterimage Effect

46. Visual Information Processing  Color Constancy  Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

47. Visual Information Processing  Color Constancy  Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object We perceive objects not in isolation, but in their environmental context is especially significant for artists and designers.

49. Audition  Audition  the sense of hearing  Frequency  the number of complete wavelengths that pass a point in a given time  Pitch  a tone’s highness or lowness  depends on frequency

50. The Intensity of Some Common Sounds

52. Audition- The Ear  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, contining the cochlea, semicurcular canals, and vestibular sacs  Cochlea  coiled, bony, fluid-filled tube in the inner ear through which

53. Audition  Place Theory  the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated  Frequency Theory  the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

54. How We Locate Sounds

55. Audition  Conduction Hearing Loss  hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea  Nerve Hearing Loss  hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

56. Subliminal Stimulation  Priming—The activation, often unconsciously, of certain associations, thus pre-disposing one’s perception, memory, or response.  “masking” stimulus that interrupts the brain’s processing  Ex. Back-masking of music  http://jeffmilner.com/backmasking/

57. Audition  Older people tend to hear low frequencies well but suffer hearing loss for high frequencies 1 time 10 times 100 times 1000 times 3264128256512102420484096819216384 Frequency of tone in waves per second LowPitchHigh Amplitude required for perception relative to 20-29 year-old group

58. Touch  Skin Sensations  pressure  only skin sensation with identifiable receptors  warmth  cold  pain

59. Two types of skin: Hairy skin: contains hair cells, which help detect movement and pressure. Glabrous skin: contains no hair cells, so the receptors in this type of skin are more sensitive. Glabrous skin is found mainly on the palms of the hands, bottoms of the feet, and on the lips.

60. Other senses Kinesthesis – the system for sensing the position and movement of individual body parts Vestibular sense – the sense of body movement and position, including the sense of balance Semicircular canals & vestibular sacs contain fluid that moves when your head rotates or tilts. This movement stimulates hair-like receptors, which send messages to the cerebellum, enabling you to sense body position.

61. Pain  Gate-Control Theory  theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain  “gate” opened by the activity of pain signals traveling up small nerve fibers  “gate” closed by activity in larger fibers or by information coming from the brain (endorphins)  Rubbing the area around the source of pain will create competing stimulation that block some pain messages

62. Taste  Taste Sensations  Sweet – energy source  Salty – sodium essential to physiological processes  Sour – potentially toxic acid  Bitter – potential poisons  Umami – proteins to grow and repair tissue  Consider your preferences and facial expressions for each of the preceding…

63. Sensory interaction  Sensory Interaction  the principle that one sense may influence another  as when the smell of food influences its taste  The McGurk Effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound.

64. Smell Receptor cells in olfactory membrane Nasal passage Olfactory bulb Olfactory nerve

65. Age, Sex and Sense of Smell Women Men 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 Age Group 4 3 2 0 Number of correct answers Women and young adults have best sense of smell

66. Body Position and Movement  Kinesthesis  the system for sensing the position and movement of individual body parts  Vestibular Sense  the sense of body movement and position  including the sense of balance