1. Myers’ EXPLORING PSYCHOLOGY (4th Ed)
Chapter 4
Sensation and Perception
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 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
Absolute Threshold
minimum stimulation needed to detect a particular stimulus
usually defined as the stimulus needed for detection 50% of the time

5. Sensation- Thresholds
Subliminal
below one’s absolute threshold for conscious awareness
Difference Threshold
the minimum difference that a person can detect between two stimuli 50 percent of the time
we experience the difference threshold as a just noticeable difference (jnd)

6. 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”

7. Sensation- Thresholds
Weber’s Law
for a difference to be perceived, two stimuli must differ by a constant minimum percentage
Sensory adaptation
diminished sensitivity as a consequence of constant stimulation

8. Vision Wavelength Hue Intensity
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

9. Vision Accommodation Retina
the process by which the eye’s lens changes shape to focus the image of objects on the retina
Retina
the light sensitive inner surface of eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

10. Vision Rods Cones retinal receptors that detect black, white, and gray
necessary for peripheral and twilight vision
Cones
receptor cells that are concentrated near the center of retina
function in daylight or well-lit conditions
detect fine detail and give rise to color sensation

11. The Eye
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

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

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

14. Visual Information Processing
Parallel Processing
processing several aspects of a problem simultaneously
the brain’s natural mode of information processing for many functions, including vision

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

16. Visual Information Processing
Young-Helmholtz Trichromatic (three color) Theory
the retina contains three different retinal color receptors- one most sensitive to red, one to green, and one to blue- which when stimulated in combination can produce the perception of any color

17. The Three Primary Colors of Light

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

19. Visual Information Processing
Opponent-Process Theory
theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision
some cells stimulated by green and inhibited by red
others stimulated by red and inhibited by green
Color Constancy
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

20. Opponent Process- Afterimage Effect

21. Audition
Visual Capture- tendency for vision to dominate the other senses
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

22. Audition- The Ear Middle Ear
the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

23. Audition- The Ear Inner Ear Cochlea
innermost part of ear, containing the cochlea, semicircular canals and vestibular sacs
Cochlea
coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

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

25. 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

26. Taste Taste Sensations Sensory Interaction sweet sour salty bitter
the principle that one sense may influence another
as when the smell of food influences its taste

27. 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

28. Perception Gestalt an organized whole
tendency to integrate pieces of information into meaningful wholes

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

30. Perceptual Organization- Gestalt
Grouping
the perceptual tendency to organize stimuli into coherent groups
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

31. Perceptual Organization- Gestalt
Proximity
Similarity
Continuity
Closure
Connectedness

32. Perceptual Organization- Gestalt Groupings
Gestalt grouping principles are at work here.

33. Perceptual Organization-Depth Perception
ability to see objects in three dimensions
allows us to judge distance
Binocular cues- depend on use of two eyes
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

34. Perceptual Organization-Depth Perception
Monocular Cues-available to either eye alone
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

35. Perceptual Organization-Depth Perception
Visual Cliff

36. Perceptual Organization-Depth Perception
Relative Size

37. Perceptual Organization-Depth Perception
Interposition

38. Perceptual Organization-Depth Perception
Monocular Cues (continued)
relative height
higher objects seen as more distant
relative motion
closer objects seem to move faster
linear perspective
parallel lines converge with distance
relative brightness
closer objects appear brighter

39. Perceptual Organization-Depth Perception
Perspective Techniques

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

41. Perceptual Organization

42. Perceptual Organization-Muller-Lyer Illusion

43. Perceptual Organization- Size-Distance Relationship

44. Perceptual Organization-Brightness Contrast

45. 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

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

47. Perceptual Set- Schemas
Flying Saucers or Clouds?

48. 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