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General Psychology 201
Sensation and Perception
Basic principles of sensation
- Sensory thresholds and sensory adaptation
- Science versus pseudoscience 3.1: subliminal perception
Vision
- What we see
- How we see (cornea, pupil, iris, lens)
o The retina (rods and cones), the blind spot
- Science versus Pseudoscience 3.2: Iridology
- Processing visual information
- Color vision (The experience of color, How we see color (the
trichromatic theory and opponent-process theory)
Hearing
- What we hear / how we hear (place theory and frequency theory)
The chemical sense and body senses
o Science versus pseudoscience: pheromones
- Taste
- The skin and body senses
Perception
- Bottom-up and top-down processing
- The perception of shape
- Depth perception (monocular cues and binocular cues)
- The perception of motion
- Perceptual constancies
- Critical Thinking 3.4: ESP
Perceptual illusions
The effects of experience on perceptual interpretations
- Culture and the Müllen-Lyer illusion
Application: Strategies to control pain
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What are some phenomena this chapter can help explain?
Taste:
- Why does orange juice taste bitter right after you brush your
teeth?
Vision:
- Why are some people color deficient (commonly called color
blind)
- Why do you see afterimages?
- What is the blind spot, why does it occur, why don’t we
notice it?
- How do we perceive depth (both with one eye and two
eyes)?
Vestibular sense:
- How does this help explain airplane crashes like JFK Jr.
(what are pilots trained to do)?
Other:
- There is very little evidence to support the claim that
people possess ESP abilities such as telepathy,
clairvoyance, psychokinesis and precognition, but about _
of American adults believe in ESP. What is one of the
many reasons why people believe in ESP?
- How do labels affect perception?
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There are some basic concepts that psychologists use when
talking about the sensitivity of the senses (page 90).
- Absolute threshold: The smallest detectable strength of a
stimuli that can be detected half the time, or 50% of the
time. This label seems counterintuitive, but it is not. Why?
- Difference threshold: The smallest possible difference
between two stimuli that can be detected half the time.
This is also called just noticeable difference (jnd).
- Weber’s law: A principle of sensation that holds the size of
the just noticeable difference (jnd) will vary depending on
its relation to the strength of the original stimulus.
- Sensory adaptation: The decline in sensitivity to a constant
stimulus. Therefore, a stronger stimulus is required to
activate the sensors.
For example, why is understanding sensory adaptation important
(in what cases would sensory adaptation be “bad”)?
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Organizing information. You should read the section on rods
and cones and organize the information in two columns.
Rods Cones
ends
- short and fatter with ends
that taper to a point
- estimated at 125 million • estimated at 7 million
- max sensitivity in about
30 minutes
- adapt to light in about five
minutes
- primarily for night vision • primarily for color vision
- there are no rods in fovea,
but more prevalent in the
peripheral areas of the
retina
- cones are concentrated in
the fovea, and less
common in the periphery
light—about 1000 time
better
- specialized for seeing fine
details and vision in bright
light.
In addition to this, you should see how this information
interrelates with material in the pictures/diagrams and
experience (such as the one on page 95).
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The Opponent Process Theory
The trichromatic theory of color perception cannot explain an
afterimage such as seeing a faint red, white and blue flag after
staring at a yellow/green flag.
According to the opponent process theory, there are three types
of color sensitive neurons that are sensitive to a certain pair of
colors:
- red / g
g g r
r r e
e e e
e e n
n n
- blue / y
y y e
e e l
l l l
l l o
o o w
w w
- black / white
One single receptor can only be activated to a single color, while
the other color is inhibited (blue can be activated, while the
yellow is inhibited). With multiple receptors, some receptors
can be sensitive to blue, while others can be sensitive to yellow.
For example,
y y e
e e l
l l l
l l o
o o w
w w
y y e
e e l
l l l
l l o
o o w
w w
y y e
e e l
l l l
l l o
o o w
w w
- Blue / yellow
- Blue / yellow
- Blue / yellow
- Blue / y
y y e
e e l
l l l
l l o
o o w
w w
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All color perceptions are a combination of these receptors. For
example,
- Orange = red/green + blue/y
y y e
e e l
l l l
l l o
o o w
w w
- Purple = red/green + blue/yellow
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Which theory of color vision is “right”,
they both can’t be right?
This is the wrong question to ask about color perception. Both
theories explain color perception, but at a different level of color
perception.
- The trichromatic theory primarily explains perception
within the structure of the eye (the cones and retina) before
being transmitted to the brain via the optic nerve.
- The opponent process theory explains perception within the
ganglion cells, thalamus and visual cortex.
Why is understanding the process of color perception important
for understanding psychology, science, and perhaps life in
general.
- No one theory explains complex behavior—it involves
multiple processes.
- Sometimes asking the wrong/right question is important for
understanding the world around you. The question that is
given to you, may be the “wrong” question.
- I hypothesize that mechanical eyes will need to be able to
produce after images and other visual illusions.
- Even though they “appear” to be inconsistent, the two
theories are consistent. Science needs to be internally
consistent
Where will you see this again?
- Motivation and Emotion
- Personality
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Theories of Sound Perception
How do we perceive
- low frequency sounds
- mid-frequency sounds
- high frequency sounds
What are examples of low frequency sounds?
What are examples of high frequency sounds?
Perception of low frequency sounds (below 500 hertz):
- The basilar membrane vibrates at the same frequency as the
sound wave
- Therefore, if the sound wave vibrates 300 times per second
(or 300 hertz), the membrane vibrates at 300 times per
second.
Perception of high frequency sounds:
- Different frequencies cause larger vibrations at different
locations along the basilar membrane.
- High frequency sounds cause maximum vibrations near the
stirrup end of the basilar membrane.
- Lower frequency sounds cause maximum vibrations at the
other end.
