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
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. 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)
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-
Thresholds
Subliminal
When stimuli are
below one’s
absolute
threshold for
conscious
awareness
0
25
50
75
100
Low Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
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
11. 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
12. Vision
Hue
dimension of color determined by
wavelength of light
Intensity
amount of energy in a wave
determined by amplitude
brightness
loudness
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
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
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.
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
26. 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
Color Constancy
Perceiving familiar objects as having
consistent color, even if changing
illumination alters the wavelengths
reflected by the object
37. 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
40. 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
41. 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
43. 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
44. Audition
Older people tend to hear low
frequencies well but suffer hearing loss
for high frequencies
1
time
10
times
100
times
1000
times
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
only skin
sensation with
identifiable
receptors
warmth
cold
pain
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
47. Taste
Taste Sensations
sweet
sour
salty
bitter
Sensory Interaction
the principle that one sense may influence
another
as when the smell of food influences its taste
49. 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
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
Hinweis der Redaktion
Complete 5.1 prior to beginning
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
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…
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
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
Lay audiences accept the idea of subliminal persuasion but it has not been substantiated in research
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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