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 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. Sensation- Thresholds
Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion
light intensity- 8%
weight- 2%
tone frequency- 0.3%
Sensory adaptation- diminished sensitivity with constant stimulation

9. Vision- Stabilized Images on the Retina

10. 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. (red to violet)
Intensity- amount of energy in a wave determined by amplitude
brightness
loudness

11. Vision- Spectrum of Electromagnetic Energy

12. 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)

13. Vision Pupil- adjustable opening in the center of the eye
Iris- a ring of muscle the 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

14. Vision

15. 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

16. 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

17. Vision
Farsighted vision nearsighted vision normal vision

18. 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

19. 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

20. 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

21. Pathways from the Eyes to the Visual Cortex

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

23. How the Brain Perceives

24. Illusory Contours

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

26. 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

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

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

29. 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

30. Opponent Process- Afterimage Effect

31. 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

32. The Intensity of Some Common Sounds

33. On the decibel scale, the smallest audible sound (near total silence) is 0 dB.

34. A sound 10 times more powerful is 10 dB
A sound 10 times more powerful is 10 dB. Memory trick- the first digit in the decibel number is the number of zeros after the 1

35. A sound 100 times more powerful than near total silence is 20 dB
A sound 100 times more powerful than near total silence is 20 dB. Note that the 2 in 20dB is the number of zeros in times as loud as the faintest sound

36. A sound 1,000 times more powerful than near total silence is 30 dB.

37. Here are some common sounds and their decibel ratings:

38. Near total silence - 0 dB

39. A whisper - 15 dB

40. Normal conversation - 60 dB

41. A lawnmower - 90 dB

42. A car horn dB

43. A rock concert or a jet engine - 120 dB

44. A gunshot or firecracker - 140 dB

46. 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

47. 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

48. How We Locate Sounds

49. Audition Conduction Hearing Loss Nerve 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

50. Audition
Older people tend to hear low frequencies well but suffer hearing loss for high frequencies 1
time 10
times
100
1000 32 64
128
256
512
1024
2048
4096
8192
16384
Frequency of tone in waves per second
Low
Pitch
High
Amplitude required for
perception relative to
20-29 year-old group

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

52. 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

53. 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

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

55. 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

56. 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