Sensation and Perception
What is Sensation and
Perception?
The Man Who Mistook His Wife for a Hat by
Sensation: the stimulation of the eyes, ears,
nose, tongue, and skin
Perception: the selection, organization, and the
interpretation, of sensory input.
Sensation vs Perception
• -What is the difference between sensation and
perception?
• - Give examples related to 3 different senses!
Psychophysics
Breakdown
• Read intro to psychophysics on pgs. 226-232.
• Pay attention to key words:
1.
2.
3.
4.
5.
6.
7.
8.
9.
bottom-up processing,
top-down processing,
psychophysics,
absolute threshold,
signal detection theory,
subliminal perception,
difference threshold [(just noticeable difference (JND)],
Weber’s law,
sensory adaptation
Word
Definition in Own
Words
Example
Media
1. bottom-up
processing
analysis that begins with
sensory observations by
your sense organs and
eventually results in the
brain putting them all
together to create a whole
meaning.
I see a picture, but I can’t
tell what it is. I look at
the edges first, then I
work my way toward the
middle. I realize at this
point that it’s a “Where’s
Waldo” picture.
In Legally Blonde
where the law professor
doesn’t realize the Elle
has handed him a
resume. “It’s pink,” he
states blankly. “And it’s
scented,” she adds.
Psychophysical Breakdown
2. top-down
processing
3. psychophysics
4. absolute threshold
5. signal-detection
theory
6. subliminal
perception
7. difference
threshold
8. Weber’s law
9. sensory adaptation
Leave room in your chart! Make
it a whole page!
• Bottom-up processing= analysis that begins with the sensory
receptors and works up to the brain’s integration of sensory
information. I see a picture, but I can’t tell what it is. I look at
the edges first, then I work my way toward the middle. I realize
at this point that it’s a “Where’s Waldo” picture.
• Top-down processing= information processing that starts with a
perception as a whole and is then broken down to its component
parts. I recognize, “Hey, that’s Mrs. Jones,” and then I notice
that she got new glasses.
• Psychophysics= the study of how physical stimuli are interpreted
mentally. Sensation and perception.
• Threshold=trigger point, like when the street lamps outside turn
on
▫ absolute threshold= minimum amount of stimulation an organism
can detect, like when you can just make out your brother’s muffled
music down the hall, but when he turns it down a notch you can no
longer hear it.
▫ signal-detection theory= our detection of stimuli depends on
expectations we have and other judgments we make on the stimulus.
(1) You can hear the doorbell in the middle of a crowded party (noise)
when you expect its about time for the pizza to arrive. If someone were
to deliver a surprise pizza, you may not detect the doorbell. (2)
Detecting enemy aircraft with radar: If you set super strict criterion
for detecting aircraft, you may not even notice weak signals. If you’ve
been told that you will likely be under attack tonight, you will notice
weak signals and be prepared to fire on them.
▫ subliminal perception= registering sensory input without conscious
awareness. Mrs. Fullbright’s hand thing.
▫ just noticeable difference (JND) or difference threshold= the smallest
difference in the amount of stimulation that a specific sense can
detect, like you can’t detect the difference between the textures of two
similar grades of sandpapers until you arrive at different enough
textures that you can tell the difference.
▫ Weber’s law= the size of the JND changes in proportion to the initial
stimulus which relies on a different % for each sense. Light
intensity=differ by 8%, weight=differ by 2 %, tones=differ by 0.3% If
you lift a 20 lb. weight and a 21 lb. weight, you’ll notice the difference.
But if you lift a 90 lb. weight, you must lift a 92 lbs weight (you
wouldn’t notice 91 lbs. as a difference) to notice a difference.
▫ Fechner’s law= the mathematical justification for Weber’s law.
Practically, constant increments is stimulus intensity produce smaller
and smaller increases in the perceived magnitude of the sensation. If you
turn on a bright lamp in a light room, you’re going to notice the increased
light less than if you would have turned on a dim light in a very dark
room.
▫ sensory adaptation= decline in sensitivity to prolonged situation. After
eating Sunchips for 45 minutes, the taste will no longer be thrilling.
(Spiral) The Optic Pathway
• We’re going to learn how the
eye works by watching a real
cow’s eye dissection.
• We’re off on a virtual field trip
to New Jersey. Lawrence
Township Public Schools
sponsors the this site:
http://ow.ly/eyO0o (capital o,
number 0, and little 0)
• Click on “Watch Online”
• Pretend you are dissecting the
eye. As you remove each of
the following parts, the claim
you are going to support is
that light interacts with each
of these biological devices.
• Describe in your own words
how each part interacts with
light.
▫ Use Myers, pgs. 234-237 as a
tool to discern what these
structures do.
▫
▫
▫
▫
▫
▫
▫
▫
▫
▫
Cornea light?
Aqueous light?
Iris
light?
Pupil
light?
Lens
light?
Vitreous light?
Retina
light?
Fovea
light?
Blind Spot light?
Optic nerve light?
Note on the Rods and Cones
• The cones are in the fovea, which is in the part of
the retina directly across from the lens. The
allow us to see detail and color.
• The rods are in the rest of the retina. Rods help
us adjust dim light and movement. They
outnumber the cones 20-1.
Still fuzzy on the eye?
• Other sources
• http://www.sumanasinc.com/webcontent/anim
ations/content/visualpathways.html
• http://www.youtube.com/watch?v=RE1MvRm
Wg7I&feature=related
Theories of Color Perception
What are the primary colors?
• Primary Colors for Additive Light:
• Red
• Blue
• Green
Additive color mixing works by superimposing lights, putting more light in the
mixture than exists in any one light by itself.
Additive Color Mixtures: What happens when
mix different wavelengths of light?
Note: Mixing paint is a “subtractive mixture.”
So the rules are different.
What color do you get when you combine all
colors of light?
WHITE! Whereas, if you combined all
possible colors of paint, which color would
result?
BLACK!
Additive Mixtures
• red + green= yellow
• Red + blue= magenta
• Blue +green= cyan
• HAVE YOU EVER THOUGHT OF
YELLOW AS A REDDISH-GREEN?
(Spiral) Theories of Color Perception
1. Read about the Young-Helmholtz trichromatic
theory and the opponent-process theory on
pgs. 240-242. Summarize each theory.
2. Do the colorblind test with figure 18.10
3. Do the afterimage experiment on figure 18.11
4. Google “Ucalgary Colour Vision” and click on
“Theories of Colour Vision” to see an
illustration of these two theories.
5. Upon completing this, it will be time to test
your understanding . . .
Theories of Color Perception: Did
you understand?
• Directions: Answer the following questions. Feel free to use the book, the
UC Calgary website, and the model below to help you.
1. How does the trichromatic theory account for colorblindness?
2. What does the phenomena known as “afterimage” prove?
3. How do we see yellow, even though we have no yellow cone receptors?
4. If your eye is absorbing blue, green, and red light, and only the yellow
part of a blue/yellow bipolar cell is inhibited, what color will you see?
5. If your eye is absorbing blue, green, and red light, and only the yellow
part of a blue/yellow bipolar cell is activated, what color will you see?
(Spiral) Gestalt Psychology: Topdown processing
• Write down the “grouping” principles of Gestalt
Perception and define them (pgs. 263). They are
proximity, similarity, continuity, connectedness,
closure, and simplicity.
• Also define the following perceptual principles:
context, linear perspective, depth and distance,
monocular depth perception, binocular depth
perception, retinal disparity, size constancy
• Illustrate each one through words, drawings, or
coming up with your own examples.
Basic Gestalt Principles
Gestalt
Psychology: topdown processing;
the whole is more
than the sum of its
parts.
Connectedness:
elements tend to be
grouped together if they
are connected by other
elements.
When Top-down processing doesn’t
work
The drawings are real,
because they’re lines on a
plane just like any other
drawing.
Why does our mind become
frustrated?
• Appear three-dimensional,
like other figures we’re used
to, so it’s difficult merely to
see them as lines drawn on
a plane
• Drawn in a way that
doesn’t let the mind
assemble them into a whole
proximity
Closure
similarity
Simplicity
Closure,
similarity
Muller-Lyer Illusion and the Ponzo Effect
Context: depth, distance, context, linear perspective
Our brains base our perception of reality on “the familiar,” like building
designs.
• Gestalt Principle: Similarity, Simplicity, Continuity
• Illusions provide hints about perceptual strategies through familiar context.
• In the Muller-Lyer illusion (above) the visual system processes that judge depth and
distance assume in general that the “angles in” (left) configuration corresponds to an
object whose corner is thrust toward you and closer, and the “angles out” (right)
configuration corresponds to an object whose corner is thrust inward and farther
away. Therefore, the “angles out” line must be bigger, since it represents the corner
that is further away. We are used to this principle having so many buildings and
structures that are rhombuses. They gives us a context to which to compare these
visual configurations.
•In the Ponzo Effect (right) the converging lines convey linear perspective, a key depth
cue suggesting that the upper line lies farther away. However, it comes closer to the
sides of the converging lines. Therefore, out brain tells us it is bigger since it is not
shrinking in proportion to the converging lines. Linear perspective provides context. Side
lines seem to converge, so our brain says, “It must be longer!”
The Ames Room
Gestalt Principle: Similarity, Simplicity, Continuity
Other Factors in Perception:
(1) The viewer is looking through a hole in the wall with one eye.
Monocular depth perception causes errors in depth and distance
judgments. With binocular depth perception, we might notice some of
the clues.
(2) Convergence and retinal disparity explain why monocular depth
perception isn’t great. You see two slightly different pictures, one
through each eye positioned at slightly different positions on your face.
However, you have one dominant eye, and your brain puts the info
from both eyes together as if you were seeing the picture with only
your dominant eye. Still, that picture has the depth and angular
perspective that comes from the info sent in by the non-dominant eye.
So, with only one eye open, you’re missing things!
(3) The room is trapezoidal. Because of the architectural context we’re
used to, we assume it’s square or rectangular.
(4) Context cues like the windows, the floor tiles, the clock, the balloon,
and the floor-to-ceiling distance relative to the child convince us that
the kids are different sizes. In reality, these context cues are different
sizes!
(5) Size constancy is the principle that allows us to assume that, even
though an object may look larger or smaller dependent upon its
proximity to the viewer, the object doesn’t actually change size.
Therefore, we assume that the two kids can’t change size if they walk
from one side of the room to the other. Consequently, one child
appears to be normal-sized, the other a giant. We see a similar
phenomena with the moon illusion.
(Spiral) The Auditory Pathway
• Use pgs. 243-247 and
http://www.youtube.com/watch?v=PeTriGTENoc to
answer the following questions:
• What is amplitude? What is frequency or pitch?
• Define how each of the following parts help produce hearing using
vibration:
–
–
–
–
–
–
–
–
–
tympanic membrane,
auditory ossicles
boney labyrinth
perilymph (fluid)
round window
cochlea (spiral system)
basilar membrane
hair cells
tectorial membrane
• What’s place theory? How do we know it exists?
• How do we locate sounds?
• What’s frequency theory? How do we know it exists?
(Spiral) The Sensory Pathway: Touch
• Use pgs. 251-257 and the video to answer the following
questions.
• http://ow.ly/eQzuj or “touch how the body works”
1. Where is the sensory cortex?
2. What are some of the different kinds of receptors in the
epidermis?
3. What are some of the different kinds of receptors in the
dermis?
4. Name the four basic skin sensations and some of their
variations.
5. How do the kinesthesis and vestibular senses connect to
touch?
6. What’s the Gate-Control Theory?
Overview
Background Knowledge
• Feeling originates in the bottom layer of the
skin, the dermis, below the epidermis, the
outermost layer of the skin.
– Dermis is filled with tiny nerve endings that
registers info.
• Carries info to the spinal cord
• Receptors are found all over in clusters around
the skin in the form of onion or jelly-like
material. Receptors are not distributed evenly.
– When squeezed, layers rub against each other
creating electrical nerve impulses.
• About 20 touch receptors
– Common: heat, cold, pain, pressure
– Sensitive: hands, lips, face, neck, tongue, fingertips,
chest, upper arm, sole of feet, and between the legs.
• The more nerve endings = the more sensitive
• Mechanoreceptors tell about sensations of
pushing, pulling, and movement
– Free Nerve Ending, Pacinian Corpuscle, Messiner
Corpuscle
• Thermoreceptors tell about sensation of
temperature.
– Krause Corpuscle, Ruffini Endings
and vibration
(Spiral) The Gustatory Pathway
• Use pgs. 257-258 and the two videos to answer these questions.
• http://ow.ly/eQzN5
• http://ow.ly/eQzQQ
1. What are the different kinds of tastes (the book adds one)?
2. Where are vallate papillae and to what tastes are they responsive?
3. Where are circumvallate papillae and to what tastes are they
responsive?
4. Where are fungiform papillae and to what tastes are they
responsive??
5. What is a taste bud made up of?
6. What regenerates taste buds?
7. How often do taste buds regenerate?
8. What’s the “lock and key” principle?
9. How do sight and smell interact with taste (“sensory interaction”)?
The Chemical Senses: Taste
• Taste (gustation)
• Physical stimulus: soluble chemical substances
▫ Receptor cells found in taste buds
Taste buds
are
clusters of
taste cells
that line
the
trenches
around
papillae
(bumps).
How Taste Happens
• Taste results from a complex blend of the 4 different “tastes.”
• Pathway: taste buds -> neural impulse -> thalamus ->
cortex
• Group Question Minute: Why would taste preferences vary
dramatically among people of different cultures and
countries?
• Taste: learned, social, biological process
 You learn to eat what people around you are eating (social).
 You eat what is available to you in your environment
(learned).
 Your taste receptors adapt to your taste preferences early in
life (biological).
 You inherit taste preferences (evolutionary)
All About Taste Buds
• Photograph of tongue surface (left), magnified 75 times.
• 10,000 taste buds line the tongue and mouth.
▫ Taste receptors are down inside the “bud”
• Taste cells only live about 10 days. They travel toward
the center of the “bud” and then die.
• Four primary tastes: sweet, sour, bitter, and salty.
Individual taste cells specialize in one of these four
areas, but each is capable of sensing all four.
• Children have more taste buds than adults.
(Spiral) The Olfactory Pathway
• Use pgs. 258-261 and the video to answer these questions.
• http://ow.ly/eQzW1
1. What is the stimulus for smell?
2. What is volatility, and how does it relate?
3. What is the olfactory membrane, and where is it located?
4. What is the olfactory membrane covered with.
5. What decides whether or not a molecule stimulates a neuron?
6. What do the structures in the olfactory bulb do?
7. Is the olfactory bulb part of the nose or the brain (see diagram in
book)?
8. How many different odors can the human brain distinguish?
9. Where is the primary olfactory cortex in the brain?
10. Which groups have the keenest sense of smell? Why?
11. Why is it difficult to name odors?
12. Describe the connection between odors and memory.
The Chemical Senses: Smell
• Smell (Olfaction) operates much like the sense of
taste in that stimuli are chemical.
• Smell determines taste, which is why you can’t
taste if your nose is stuffed up.
• Physical stimuli: substances carried in the air
▫ dissolved in fluid, the mucus in the nose
• Olfactory receptors=olfactory cilia and are
located in the upper portion of the nasal
passages.
• Chemicals
dissolve in mucus
and travel to the
cilia.
How Smell Happens
• Pathway:
Olfactory cilia ->
neural impulse ->
olfactory nerve ->
olfactory bulb
(brain) and then to
the limbic system
and other parts of
the brain
Does not go
through
thalamus
So, what is different about smell?
• Odors are not easily classified, and primary odors
have not really been delineated. Humans can
distinguish among about 10,000 odors, but for some
reason have a hard time attaching names to odors
quite frequently.
• Why do people have a hard time attaching names to
odors as opposed to taste and visual perceptions, for
example?
•
•
•
•
Odors are invisible.
Odors are transient.
Odors are sometimes unexpected.
Therefore, odors’ lack of “concreteness” affects our ability to
verbally classify them into “types.”
Checking Your Knowledge- Senses
• Use your presentation notes from your
classmates to complete the following knowledge
checks.
• Concept Check 4.3- Comparing Vision and
Hearing (pg. 158)
• Concept Check 4.4- Comparing Taste, Smell,
and Touch (pg. 164)
Pick a Sense
• Choose a sense about which you feel you still
know little.
• Your choices:
▫
▫
▫
▫
Vision (various aspects)
Hearing
Smell and Taste
Touch
• Research it in our text book or others focusing
on (1) structure of the sense organ and (2)
process of transduction.