Unions are relics of the past and are no longer relevant in the world economy in which
we live.
OR
Despite a declining membership, unions continue to fill an important role in our society
and economy.
Please discuss either one of these positions and support your arguments with some
concrete facts. You may have to go online to get some additional information on this
topic. After discussing this with your fellow students, please post a short summary
comment in the assignments folder. This subject is your only Week 6 homework
assignment.
Chapter 5: Sensation
I. Basic Principles
A. Thresholds
1. Absolute Thresholds: the minimum mount of stimulation a person needs for
a particular stimulus to be detected 50% of the time.
What is your absolute threshold?
2. Signal detection theory: Detection of weak signal. Measured as our ratio of
hits to false alarms
Signal detectors will increase or decrease depending on the response,
time of day, and on the physical health of a person
Ex. parents, no matter how exhausted will notice the faintest sounds made
by the infant, but will be unaware of other louder noises.
3. Subliminal Stimulation
Ex. Self help audiotapes for smoking and alcohol ? soothing sounds that mask
messages ?I am thin? "Smoking is bad?
Research has demonstrated that we can detect subliminal stimuli and that we
can process information without being aware of it.
Can advertisers manipulate us with subliminal messages? Most research
psychologists say NO!.
Ex. experiment conducted in Canada in which during a popular television
show a subliminal message was flashed 352 times .% Not one of the 500
people who responded were able to identify the subliminal message ?
Telephone Now?
4. Difference Thresholds: Difference threshold or just noticeable difference, is
the minimum difference that a person can detect between two stimuli
Why is it important? In order for wine tasters to be able to detect the slightest
of differences between wine flavor and for parents to be able to detect their
child?s voice over that of another
In order to perceive the difference, the two stimuli must differ by a constant
minimum percentage, rather than a constant amount ? This is Weber?s law!
B. Sensory Adaptation
Diminished sensitivity to an unchanging stimulus
Ex. move your watch up and down ? you can feel it but, only for a few
moments
II. Vision
A. Stimulus Input
We do not see color, but rather pulses of electromagnetic energy
Our visual system of our brain, experiences it as color
Figure 5.3 ? Electromagnetic Spectrum ranges from very short gamma rays to
very long radio waves.
Shorter waves = blue-violet light
Longer waves = red light
There are 2 physical characteristics of light and sound that help us to
experience each of them.
1) Wavelength: distance from one peak to the next will determine its hue
(color)
Short wave = high frequency = blue, high pitched sounds.
Long wave = low frequency = red, low pitched sounds.
2) Intensity: amount of energy in light waves that influence brightness.
Greater amplitude = brighter color, loud sounds
Smaller amplitude = dull color, soft sounds
B. Eye
Light enters through the cornea, then passes through the pupil (a small
adjustable opening in the center of the eye). Size of the pupil is regulated by
the iris ? color of the eye
From the pupil, light enters the lens. The lens, then changes shapes to focus
image on the retina . The process of changing shapes to focus near objects on
the retina is accommodation
Retina is the light sensitive inner surface of the eye where the processing of
visual information occurs.
1. Retina contains rods and cones.
Rods enable black and white vision, cones enable color. Rods are sensitive in
dim light, the cones are not ? this is why you do not see color in dim light.
When you enter a theater your pupils dilate to allow more light to reach the
rods in the retina. It typically takes 20 minutes before your eyes fully adapt.
2. Vision type
Normal vision: rays of light converge on the retina, for near objects and
readjust for distance objects
Nearsighted: rays of light from distant objects focus in front of the retina,
when the information reaches the retina, rays are spread out and the image is
blurred.
Farsighted: rays of light from near by objects focus behind the retina, blurring
the image.
3. Blind spots
There are no receptor cells where the optic nerve leaves the eye, creating a
blind spot in our vision
Ex. figure 5.8
C. Visual Information Processing
Visual cortex receives information from the eyes by way of the optic nerves,
which come together at the optic chiasm. From here information gets
transmitted to the thalamus in the visual cortex.
Try this example! Turn your eyes to the left, close them, and then gently rub
the side of your right eyelid with your fingertip. Note what you see. Results:
your retinal cells are so responsive that even pressure triggers them. Your
brain interprets their firing as light and it interprets the light as coming from
the left ? the direction light normally comes from when it activates the right
side of the retina.
1. Feature Detection: nerve cells in the brain that respond to specific
features of a stimulus ? shape, angle or movement
Look at the Necker cube in figure 5.11.% Our visual system works both
bottom up and tops down and thus the image will change every few seconds.
2. Parallel Processing
Our brains can do several things at once e.g., vision
Vision is divided into color, motion, form and depth
D. Color Vision
1. Trichromatic Theory
Color vision was very much a mystery until ? Hermann von Helmholtz and
Thomas Young discovered that any color can be created by combining the
light waves of 3 primary colors ? RED-GREEN-BLUE. They inferred that the eye
has a receptor for each of the primary colors.
Young-Helmholtz trichromatic theory. Retina has 3 types of color receptors
each sensitive to one of the 3 colors.
Making other colors is not like mixing paints (subtractive color missing). The
more colors you put in, the fewer wavelengths that can be referred back.
Mixing light is additive color mixing. Adds wavelengths and thus increase
light.
Color deficient vision· Figure 5.17
· Color blind or color deficient people lack red or green sensitive cones.
Genetically sex linked trait
2. Opponent Process Theory
Figure 5.18. Stare at the image and then at the black dot, you should see
its opponent color-red
Hering propose color processes. RED vs. GREEN, BLUE vs. YELLOW, WHITE vs.
BLACK which is known as the Opponent Process Theory (stimulated by one
color, but inhibited by the other)
IV. Hearing
A. Sound Waves
strength and amplitude of sound waves = loudness
soundwaves vary in length and therefore frequency
frequency determines pitch
long wave length = lower pitch short wave lengths = higher pitch
decibels ? measuring unit for sound, pg. 212
GENERAL RULE?If you can not talk over noise it is potentially harmful?
B. Ear ? How does the information get in?
outer ear moves sound waves through the auditory canal to the eardrum
middle ear, transmits the eardrums vibrations through a piston made of three
tiny bones ? hammer, anvil and stirrup- to the inner ear, called the cochlea
vibrations cause the cochlea to vibrate the fluid within the cochlea
motion causes ripples in the basilar membranes which is lined with hair cells.
Hair cells bend and their movement triggers impulses at the base of the nerve
cells, whose fibers converge to form the auditory canal
Sound waves send neural messages up to the temporal lobe of an auditory
cortex
1. Pitch
High pitch versus low pitch. How can we perceive which is which?
a. Herman von Helmholtz Place Theory: Explains high pitch sounds
b. Frequency Theory: Explains low pitch sounds
c. Volley Principle: Combines both
2. Locate Sounds
We localize sounds by detecting small differences in the loudness and
timing of the sounds received by both ears
Perceived direction of sound is related to differences in the time at which the
sound is received by each ear
C. Hearing Loss and Deaf Culture
Between 17 and 20 million Americans suffer some hearing loss, making this
the most common disability.
At every age men exhibit greater hearing loss than women.
Take this test!· Test hearing : hold hand up to your shoulder and rub your
fingers together. If you do not clearly hear a high pitched scratching sound,
you may have some hearing loss in that ear.
Conduction hearing loss: damage to the mechanical system that conducts
sound waves to the cochlea (ex. punctured eardrum)
Sensorineural hearing loss: caused by disease, again, prolonged exposure to
noise or music
V. Other Senses
A. Touch
Touch is made up of pressure, warmth, cold and pain
Pressure, is the only part of touch that has identifiable stressors
Relationship between the others is unknown
Touching various areas of the skin will reveal that some spots are more
sensitive to warmth, others cold, other pain. Touch localization
Ex. Touch localization: touch two indexes fingers together. On which two
fingers is the sensation of touch felt? Both. Next, touch the lower lip with light,
quick touches. Sensation is now on the lip and little on the finger although
both are being stimulated. Now do the same quick touch to your ankle.
Sensation is located primarily on the finger. Touch localization depends on the
relative lengths of the pathways from the stimulated parts to the brain.
1. Pain
It is estimated that over 100 million Americans suffer chronic pain. The
most common being headaches, low back pain, arthritis.
Pain can be stimulated by many different stimuli. Pain can also produce other
sensations ? warmth, cold, smooth, rough, itchy
a. Theory of pain ? Gate Control Theory
Pain signals are blocked or allowed to pass through. When injured gate open
and we feel pain. Right now our gates are closed. Treat pain by stimulating it ?
to block pain messages. Rub the area around the injury and you can
accomplish this. Ice on a bruise closes the gate.
b. Pain Control
Firewalking pg. 223
B. Taste
Also involves 4 sensations ? sweet, sour, salty, bitter
Taste receptors reproduce itself every week or two
Smoking and alcohol will also decrease taste buds
Tastes also involved smell, which adds to our perception of taste
Ex. hold your nose and bite a piece of an apple, pear, potato, onion. You will
be unable to distinguish the two.
C. Smell
How smell works is unknown
D. Body position and movement
Kinesthesis: system for sensing the position and movement of individual body
parts
Ex. remember spinning as a child and suddenly stopping ? felt like you were
still spinning
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