1. Sensation
&
Perception
Chapters 5&6

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 Bottom-Up Processing Top-Down 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

4. 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

5. Sensation- Thresholds
Absolute Threshold
minimum stimulation needed to detect a particular stimulus
usually defined as the stimulus needed for detection 50% of the time
Difference Threshold
minimum difference between two stimuli that a subject can detect 50% of the time
just noticeable difference (JND)
increases with magnitude

6. 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

7. Sensation- Thresholds25 50 75
100
Low
Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”.

8. Receptors Environmental information (stimuli) exist in many forms:
Air vibrations, gases, chemicals, tactile pressures
The body receives these forms through specialized cells:
Receptor cells
E.g., taste buds

9. Receptors Receptor sensitivity is subject to change Sensory adaptation
Decline in receptor activity when stimuli are unchanging
E.g., noticing a bad smell at first

10. Receptors Habituation
Decline in sensory sensitivity at neural level due to repeated stimulation
Different from adaptation since responsiveness can reappear if stimulation level increases or decreases

11. Vision- Stabilized Images on the Retina

12. Vision Transduction- conversion of one form of energy to another
Wavelength- the distance from the peak of one wave to the peak of the next
Hue- dimension of color determined by wavelength of light
Intensity- amount of energy in a wave determined by amplitude
brightness
loudness

13. Vision- Spectrum of Electromagnetic Energy

14. 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)

15. 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

16. Vision

17. Vision Accommodation Retina change in shape of lens focus near objects
inner surface of eye
light sensitive
contains rods and cones
layers of neurons
beginning of visual information processing

18. Vision Acuity- the sharpness of vision Nearsightedness Farsightedness
nearby objects seen more clearly
lens focuses image of distant objects in front of retina
Farsightedness
faraway objects seen more clearly
lens focuses near objects behind retina

19. Vision
Farsighted Nearsighted Normal Vision Vision Vision

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

21. 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

22. Pathways from the Eyes to the Visual Cortex

23. Visual Information Processing
Feature Detectors
neurons in the visual cortex respond to specific features
shape
angle
movement
Stimulus
Cell’s
responses

24. How the Brain Perceives

25. Illusory Contours

26. Visual Information Processing
Parallel Processing
simultaneous processing of several dimensions through multiple pathways
color
motion
form
depth

27. Visual Information Processing
Scene
Retinal processing:
Receptor rods and
conesbipolar cells
 ganglion cells
Feature detection:
Brain’s detector cells
respond to elementary
features-bars, edges, or
gradients of light
Abstraction:
Brain’s higher-level cells
respond to combined
information from
feature-detector cells
Recognition:
Brain matches the
constructed image with
stored images

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

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

30. 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

31. Opponent Process- Afterimage Effect

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

33. The Intensity of Some Common Sounds

35. Audition- The Ear Outer Ear Middle Ear Inner Ear Auditory Canal
Eardrum
Middle Ear
hammer
anvil
stirrup
Inner Ear
oval window
cochlea
basilar membrane
hair cells

36. Audition Place Theory Frequency 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

37. Taste 4 basic sensations – sweet, sour, salty and bitter
All taste is a mixture of these
Taste is a chemical sense
Taste buds
Sensory interaction

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

40. Age, Sex and Sense of Smell
Women
Men
Age Group 4 3 2
Number
of correct
answers
Women and young adults
have best sense of smell

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

42. 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

43. Pain Control
Drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation training, and thought distraction
Lamaze
Psychological aspects of pain

44. 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

45. Vestibular sense - the sense of body movement and position, including the sense of balance
Semicircular canals – pretzel
Vestibular sacs – connect the canals to the cochlea
Move when we move our head
Hairlike receptors

46. Sensory Restriction
Kissing
Aphasia – ability to comprehend language
Loss of a sense
1st experiments – Sensory Deprivation – disoriented, hallucinations
Sensory restriction does not disturb most people
It reduces stress
More open to positive influence
Behavior modification
REST – restricted environmental stimulation therapy
Bottom-Up
Chapter 6 Top-Down

47. If you had to lose one sense, which would it be?
If you could only have one, which would it be?

48. Perception
Selective Attention focus of conscious awareness on a particular stimulus

49. Perceptual Illusions

50. Perceptual Organization- Gestalt
Visual Capture
tendency for vision to dominate the other senses
Grouping
the perceptual tendency to organize stimuli into coherent groups

51. Perceptual Organization- Gestalt
Gestalt- an organized whole
tendency to integrate pieces of information into meaningful wholes
Grouping Principles
proximity- group nearby figures together
similarity- group figures that are similar
continuity- perceive continuous patterns
closure- fill in gaps
connectedness- spots, lines and areas are seen as unit when connected

52. Perceptual Organization
Figure and Ground organization of the visual field into objects (figures) that stand out from their surroundings (ground)

53. Perceptual Organization- Grouping Principles

54. Perceptual Organization- Grouping Principles
Gestalt grouping principles are at work here.

55. Perceptual Organization-Depth Perception
ability to see objects in three dimensions
allows us to judge distance
Binocular cues
retinal disparity
images from the two eyes differ
closer the object, the larger the disparity
convergence
neuromuscular cue
two eyes move inward for near objects

56. Perceptual Organization-Depth Perception
Visual Cliff

57. Perceptual Organization-Depth Perception
Monocular Cues
relative size
smaller image is more distant
interposition
closer object blocks distant object
relative clarity
hazy object seen as more distant
texture coarse --> close fine --> distant

58. Perceptual Organization-Depth Perception
Relative Size

59. Perceptual Organization-Depth Perception

60. Perceptual Constancy Perceptual Constancy
perceiving objects as unchanging despite changes in retinal image
color
shape
size

61. Perceptual Organization

62. Perceptual Organization-Muller-Lyer Illusion

63. Perceptual Organization- Size-Distance Relationship

64. Perceptual Organization-Brightness Contrast

65. Perceptual Interpretation
Perceptual Adaptation
(vision) ability to adjust to an artificially displaced visual field
prism glasses
Perceptual Set
a mental predisposition to perceive one thing and not another

66. Perceptual Set- Schemas
What you see in the center is influenced by perceptual set

67. Perceptual Set- Schemas
Flying Saucers or Clouds?

68. Perception without Sensation?
Extrasensory Perception
controversial claim that perception can occur apart from sensory input
telepathy
clairvoyance
precognition
Parapsychology
the study of paranormal phenomena
ESP
psychokinesis