1. Myers’ PSYCHOLOGY (6th Ed)
Chapter 5
Sensation
James A. McCubbin, PhD
Clemson University
Worth Publishers
Complete 5.1 prior to beginning

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
5.2 Top Picture—to show the difference between sensation and perception. Looks like a meaningless blotch, students will try to figure it out—stimulation/sensation is being received but not perceived. The subject is a dog, and only part of a dog. Students will probably try to see the whole dog; you cannot tell figure from ground
5.2 Bottom picture—Fraser Spiral—it looks like a spiral but is actually a set of concentric circles

3. Sensation
Our sensory and perceptual processes work together to help us sort out complex processes
The Forest Has Eyes is the title of this work---in studying it we look at the expressions on the faces, there is something foreboding about this picture, and after we have read the title we notice other things…

4. 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
Top Down is the involvement of the brain in making meaning out of stimuli. For example there are people who can see everything clearly (sensation) but cannot recognize even their own faces (perception).
Placing meaning to sensations and stimuli is the act of perception

5. 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

6. 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)
Three methods to test
Method of Limits: begin with a minimal stimulus and increase until it is perceived by subject
Method of right and wrong cases: subject sees identical stimuli repeatedly and says yes if perceives them or it they are different, and no if not perceived or the two are not different—informs how likely it is that any given stimulus level or difference between stimuli will be perceived by subject.
Method of adjustment—adjust a comparison stimulus until it appears to be identical to the standard stimulus, errors occur and are noted then averaged to give a measure of jnd
Try the timer in the kitchen—put it in a quiet room, move away and then move back—the point at which the ticking is perceived is the absolute threshold, at that point they may be able to hear sometimes and others time not, needing to move a few feet one way or the other—lapses of attention, fatigue other factors influence

7. 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

8. Sensation- Thresholds25 50 75
100
Low
Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
Subliminal
When stimuli are below one’s absolute threshold for conscious awareness
Lay audiences accept the idea of subliminal persuasion but it has not been substantiated in research

9. 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
Try the following experiment: two envelopes, one with two quarters in it, the subject will be able to tell the difference, but then put the envelopes in a pair of shoes and try to tell the difference
Weber's Principle: difference thresholds grow with the magnitude of the stimulus
If you make $5 p/h a 25 cent hour raise will be noticeable but at $10 p/h you may need 50 cents.
If you are in sales, three piece suit and sweater, sell the suit first because after the suit the man will be more likely to buy
In car sales, after the sale customer won’t really notice $500 stereo
ADAPTation—habituation
After drinking tea with lemon, a grapefruit will not taste as sour
…but after a roll, it will taste especially sour
After holding salty water in mouth, it will taste less salty, and drinking fresh water afterwards, it will taste sweet

10. Vision- Stabilized Images on the Retina
5.3—to demonstrate that the eye is always moving
5.3 a—looking at the center will lead to the perception of movement, stare for 30 seconds and then stare at a white surface (wall or paper) , most will see after image of rotary motion
5.3b---stare at black dot in the middle for about 60 seconds and then look at the white dot, even if try to look hard, still will see an image of the grid pattern jiggling on top of the figure due to involuntary eye movements
5.3c—stare at the fuzzy contoured disc on the right, after about 30 seconds the disc will disappear, but this is almost impossible to do with the sharp contoured disc because the fizzy image jiggling on the retina causes only slight changes in the amount of light stimulating the receptors and if eyes are kept still this small change is not enough to maintain perception and disc fades from view. On the sharp one, the slight jiggling of the eyes causes sharp contour to fall first on some receptors and then on others so the amount of light stimulating the receptors is constantly changed and disc remains visible

11. Vision Transduction Wavelength
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

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

13. The 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. The blind spot occurs is the location in the retina where the visual cortex exits to the brain, there are no receptors there
What our brain does, typically, is fill in that missing piece based on what it estimates to be there
Blindsight—we can see things we don’t perceive

18. Vision
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

19. 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

20. Vision
Normal Nearsighted Farsighted Vision Vision Vision

21. 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

22. 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

23. Retinal ganglion cells---go back to 5.3 and then to 5.4
5.4a is the cover of a catalog and students complained of seeing gray spots
The grid pattern is called the Hermann grid after the German physiologist who first discovered it
The elusive gray spots can be explained in terms of the receptive fields of the retinal ganglion cells
Some of the cells are an on center surrounded by an off (like a donut). Light has opposite, antagonistic effects

24. 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

25. Pathways from the Eyes to the Visual Cortex

26. Visual Information Processing
Feature Detectors
nerve cells in the brain that respond to specific features
shape
angle
movement
Stimulus
Cell’s
responses
Feature detectors respond to specific features of a scene, edges, lines, angles, movements, and from these the brain assembles the perceived image
Illusory Figures
5.6a—just three dots produce a triangle
5.6—the last three on the page highlight the complexity of illusory figures, curved vase, x-mas tree, 3-d pyramid

28. How the Brain Perceives

29. Illusory Contours

30. Visual Information Processing
Parallel Processing
simultaneous processing of several aspects of a problem simultaneously

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

33. Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design
5.7 is an initial test for color blindness, students with scores above 16 have an 81 percent chance of failing a standard screening for color vision
8 percent of males, .05 percent of females show color weaknesses
Color defects are genetically transmitted, recent research has conclusively mapped this transmission
Monochromats—have no or only one type of functioning cone type and respond to light like a black and white film—colors are records only as gradations of intensity, likely to find daylight uncomfortable if no functioning cones, those with one cone okay but still can’t discriminate colors—very small number of people have this
Dichromats—one malfunctioning cone system, depending on type, various colors will not be perceived, inability to perceive blue is the rarest, in 1950 England, found 17 people

34. 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
5.9—shows that colors can be subjective, no wavelengths of light
Look in the center of this and many people will see wavy patterns of pastel , because the eye is constantly moving and these movements displace the image of the diagonal lines over the retinal receptors and create a pattern of receptor activity that typically occurs from viewing colored stimuli

35. Opponent Process- Afterimage Effect

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

37. 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

38. The Intensity of Some Common Sounds
A recent U of Tenn. study found that 60 percent of college students suffer some high-frequency hearing loss
Loud music is believed to be the culprit
Live concerts—120 + decibels, louder than jack hammer, chainsaw
OSHA says that 85 decibels (food processor) 8 hours, 5 days a week will eventually cause permanent hearing loss
For each 5 decibel increase, the time it takes to cause lasting injury drops by half
Try: hold finger up as if taking a court room oath, rub thumb, finger together and should hear a scrtiching sound---if not, MAY have hearing loss

40. Audition- The Ear Middle Ear Inner Ear Cochlea
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

41. 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

42. How We Locate Sounds
Experiment—have someone sit in front of class with eyes closed. Clap hands around head and ask student to identify where the sound comes from—will be able to do so when the sounds come from one side or the other, but less clearly able to do so when the sounds overhead in back or in front
The perceived difference in sounds is related to the time at which the sound is received

43. 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
Ringing in the ears is called tinnitus, affects more than 36 million Americans
Most common cause is exposure to loud noises, but also can be caused by certain drugs, ear infections, food allergies
In most severe form, this ailment is incapacitating

44. 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

45. Touch Skin Sensations pressure warmth cold pain
only skin sensation with identifiable receptors
warmth
cold
pain
Touch localization demonstration, concentrate on where the sensations of touch are felt:
Touch two index fingers together, feel it in both
Touch finger to bottom lip, light taps, felt mostly in lip even though both are being stimulated
Touch ankle, now its felt mostly in finger
Touch localization depends on the relative lengths of the pathways from the stimulated parts to the brain

46. 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
Pain is an important signal to our bodies
The experience of pain can be influenced by information from the brain
Chronic pain—est. that over 100 million people suffer from this
One study had teen age burn patients undergo a few minutes of wound treatment while they played Nintendo or while they were in a virtual reality environment—the patients felt less pain and spent less time thinking about their pain in virtual reality than Nintendo due to concept of “presences”—illusion of going inside another world. Pain requires attention

47. 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
Some taste sensations are genetically programmed, such as sweet, and finding bitter and sour foods unpleasant
A study of babies had sweet eliciting smiles, lip smacking, and sour eliciting protrusion of tongue
These reactions make good evolutionary sense
Animals tend to be neophobic, and human children are reluctant to try new things
One experiment asked a group of subjects to taste two groups of food (that were the same). When the items were accurately named (chopped tomatoes, oatmeal, beefsteak) more willing them when given novel names (pendula fruit, lat, langua steak)
However, as true with other stimuli , mere exposure makes us like them more

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

49. 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
Smell can be used to identify gender
The phenomenon of women in the same home having the same menstrual cycle is related to smell—researcher Martha McClintock discovered this 30 years ago while at Wellesley College; now a researcher at the U of Chicago found that smell can stimulate ovulation
Citrus odors make people more alert, spiced apple helps relaxation
Pumping certain pleasant food odors cut by 40 percent shoving, pushing in New York subways
People in New York mall were more likely to help strangers when there was the aroma of roasting coffee or baking cookies
Good and Plenty licorice combined with cucumber increased female blood flow by 14 percent (anything over 10 percent was considered stimulating), baby talc 13 percent, lavender + pumpkin pie 11 percent
Cherry cut flow by 18 percent, charcoal barbecue 15 percent, men’s cologne by 1 percent
Women seem to be excited by things that remind them of childhood, or are fresh smelling, relating to safety and security needed in order to feel sexual

50. 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
Ian Waterman, after viral infection, lost his sense of light touch and body position and movement—can walk but must look at limbs to direct them
When lights go out, he falls and cannot get up again until they come back on
When he is not looking at his body, he moves very little, unlike most of us who move around quite a bit
Synesthesia—sensory condition in which stimulating one modality leads to perception in another (to perceive together)
1 in 2,000 occurrence, females outnumber 6 to 1, seems to run in families so there may be a genetic base