Title: Sensation and Perception
1Sensation and Perception
2- Sensation the process of detecting physical
energy and transforming it into neural signals - This transformation process is called
transduction - Perception selecting, organizing, and
interpreting sensations - Do we see the world as it actually is?
- Nope.
- The world we see is a construct of our minds.
There is no color. There is no sound.
3- Bottom up processing Sensation to perception.
Body to brain.
4- What is the smallest amount of something you can
sense? - Absolute threshold the minimum amount of
stimulation you can detect 50 of the time - Try it..
- Some common absolute thresholds include
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11- Why 50 of the time?
- Signal Detection Theory our ability to sense
things is influenced by our - Experience some people are trained to detect
specific things (police officers) - Expectations you may/may not be ready (clowns)
- Motivation you may/may not care
- Level of fatigue/alertness you might be tired
12Subliminal messages
- Can we be influenced by things below our absolute
threshold? - Can we be manipulated through subliminal
messages? - Yes and no
- They may have a brief effect
- Priming
- Studies have shown that subliminal messages do
not produce a lasting outcome
13A_ _OM_BI_E
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16- How much does a stimulus have to change before we
notice a difference? - For example, how bright does a light need to be
before we can tell it is brighter? How much does
a sound need to change before we can tell it is
louder? - Difference Threshold/Just Noticeable Difference
(JND)- minimum difference between two stimuli
required for detection 50 of the time
17 18- Webers Law to be perceived as different, two
stimuli must differ by a constant minimum
percentage - In other words, its not the amount of stimuli
that matters, its the percentage its the ratio
of the second stimulus to the first - Light intensity 8
- Weight 2
- Tone frequency - .3
19Other examples
- Suit and sweater, which first?
- New cars
20Sensory Adaptation
- Diminished sensitivity as a result of constant
stimulation - Do you notice the chair pressing against your
legs? - If you put a band aide on, very soon you wont
notice it - So then if you stare at something, shouldnt it
disappear as the sense receptors in your eye
become used to it?
21- Yes
- It should..
- It would..
- But
- Your eyes are always moving, even when you stare
- Try this
22Phototransduction
- Conversion of light energy into neural signals
the brain can understand
23Light and color
- Light can behave as a wave or a particle
- Wavelength the distance from the peak of one
wave to the peak of the next
24- Hue (color) dimension determined by the
wavelength of light
25Wavelength (Hue)
Violet
Green
Indigo
Blue
Yellow
Orange
Red
400 nm
700 nm
Long wavelengths
Short wavelengths
Different wavelengths of light result in
different colors.
26- Intensity amount of energy in a wave,
determined by amplitude (i.e. how bright a
light is)
27Intensity (Brightness)
Blue color with varying levels of intensity. As
intensity increases or decreases, blue
color looks more washed out or darkened.
28The spectrum of electromagnetic energy
29Parts of the Eye
- Cornea outer covering
- Pupil adjustable opening in center of eye
- Iris muscle that controls the pupil
- Lens- transparent structure behind the iris that
changes shape to focus images - Retina inner surface of the eye. Contains
receptor rods and cones, and a bunch of other
neurons (bi-polor, ganglion cells)
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32- 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
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34Rods
Cones
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36- Nearsightedness nearby objects are seen more
clearly - Farsightedness faraway objects are seen more
clearly
37- Optic nerve- carries neural impulses from the eye
to the brain - Fovea- central point in the retina, where the
eyes cones cluster - Blind spot
- See if you can find your blind spot..
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39Processing visual information
40Feature Detection
41- Parallel processing processing several aspects
of a problem simultaneously - Blindsight seeing without seeing. Huh?
42Color Vision
- Trichromatic theory (Young-Helmholtz) since any
color can be created by combinations of red,
blue, and green, the eye must have three types of
receptors for these three colors - Subtractive- subtracts wavelengths from the
reflected light - Additive
43Color blindness
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45- 8 of males show a color weakness, but only .05
of females - Whos better at discriminating color?
- Why?
46Opponent-Processing theory
- Yellow is a mixture of red and green light, but
people blind to red and green can often see
yellow. How is this possible? - Afterimages
47After Images
- Stare at the eye of the red parrot while you
slowly count to 20, then immediately look at one
spot in the empty birdcage. The faint, ghostly
image of a blue-green bird should appear in the
cage.
48Opponent Colors
Gaze at the middle of the flag for about
30 Seconds. When it disappears, stare at the dot
and report whether or not you see Britain's flag.
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50ComplementaryAfterimages
51- In the nervous system, color processing cells are
grouped together like this - Red-green
- Blue-yellow
- Black-white
- When you stare at one color, you exhaust that
receptor, so when you look at a white page, you
see the opponent color
52Opponent Process Theory
Hering proposed that we process four primary
colors combined in pairs of red-green,
blue-yellow, and black-white.
Cones
Retinal Ganglion Cells
53Color Constancy
- Color is relative
- The color you see depends on the context
54Hearing (audition)
55What causes sound?
- Molecules bump into each other at different
rates, causing small changes in air pressure.
Your brain converts these changes to neural
impulses that it interprets as sound - Sound energy is measured in decibels
- Absolute threshold for hearing is 0 decibels, a
loud thunder crack is 120
120dB
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57Parts of the ear
- Sound travels through your outer ear and causes
your eardrum to vibrate - these vibrations are then transferred to the
middle ear where they cause three bones called
the hammer, the anvil, and the stirrup to
vibrate - The vibrations cause the fluid in the cochlea to
ripple - These ripples bend tiny hair cells
- The hair cells send neural messages to the brain
- hearing
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59- Loudness is determined by the number of activated
hair cells - Pitch
- Place theory
- Frequency theory
60How does the brain locate sounds?
- Snap
- Above head
- Directly behind head
- Directly in front of head
- On sides of head
61Hearing loss
- Conduction hearing loss
- Nerve hearing loss
- Cochlear implants
- Sensory compensation
62 63Touch
- Mixture of pressure, warmth, cold, and pain
- Only pressure has specific nerve receptors
- Braille 1824
- Ian Waterman no sense receptors for light
touch, body position and movement, hot and cold - Has learned to move through vision
- What happens when the lights go out?
- Touch localization
- Two-point thresholds
64Pain
- A product of the body and the brain
- Phantom limbs
- Gate control theory
- Sensitivity to pain
- Reducers and Augmenters
- People who feel no pain
- Pain control
- Distraction
- 2.50 pill, and .10 cent pill
- 85 61
65Taste
- Chemical sense
- Taste buds
- Regeneration
- Super tasters- most
- taste buds
- everything is
- intense
- Tasters
- Non-tasters
66Taste
Traditionally, taste sensations consisted of
sweet, salty, sour, and bitter tastes. Recently,
receptors for a fifth taste have been discovered
called Umami.
Sweet
Salty
Sour
Bitter
Umami (Fresh Chicken)
67Taste
- You can become accustomed to tastes (culture?)
- Experience plays a role too. Ever gotten sick
after eating a specific food? - Your sensitivity to taste will decline if you
- Smoke heavily
- Consume large amounts of alcohol
- Grow older
- Synesthesia
68Taste
- Culture and taste preferences
69Smell
- Peaks in early adulthood and then declines (like
the other senses) - Chemical sense (receptor cells in nasal cavity)
- Not filtered by thalamus
- Smell and memories
- Who has the best
- sense of smell?
70- Anosmia inability to smell
- Taste
- Weight loss
- Gas appliances
- Body odor
- How good are we at identifying smells?
71- Anticipated Identifiability Actual
Identifiability - 1. ammonia 1. Johnsons baby powder
- 2. coffee 2. chocolate
- 3. mothballs 3. coconut
- 4. perfume 4. Crayola crayons
- 5. orange 5. mothballs
- 6. lemon 6. Ivory soap (bar)
- 7. bleach 7. Vicks VapoRub
- 8. vinegar 8. Bazooka bubble gum
- 9. nail polish remover 9. coffee
- 10. peanut butter 10. caramel
72- Can you tell someones gender by smelling them?
- Hands experiment 80 accuracy
- T-shirt experiment
- Pheromones
- T-shirts again 6 men
- Women preferred the men who had an immune system
gene similar to their own (one they inherited
from their fathers) - Subliminal smells good, bad, and neutral
ratings
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74Body Position
- Kinesthesis
- Vestibular sense
- One foot balancing
- Chair experiment
- Field dependence/
- independence
75Perception
76What do these letters spell?
77What do these letters spell?
78What do these letters spell?
79- Top-down processing basically, how we make sense
of sensory input
Aoccudrnig to rscheearch at Cmabrigde Uinervtisy,
it deosnt mttaer in what oredr the ltteers in a
wrod are, the olny iprmoetnt tihng is that the
frist and lsat ltteer be at the rghit pclae. The
rset can be a toatl mses and you can still raed
it wouthit porbelm. This is bcuseae the huamn
mnid deos not raed ervey lteter by istlef, but
the wrod as a wlohe.
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82Selective Attention
- We focus on only a small amount of our experience
at a time - But because we can rapidly shift our attention,
it feels like we are able to focus on many things
at once - Cocktail party effect one voice
- Mutli-tasking
83Inattentional Blindness
- We miss things because our attention is directed
elsewhere - Jabbawocky penguin Gorilla
- Change blindness when our vision is interrupted,
we have a more difficult time noticing changes - Choice blindness switched photos
84Illusions
- The firing of certain cells that are sensitive to
light-dark boundaries inhibits other cells that
would detect the white lines. This blocking
process makes you sense darker regions
85Poggendorf Illusion
Muller-Lyer Illusion
86Visual Capture
- Vision is the dominant sense when competing with
other senses
87Gestalt Psychology
- From the German word meaning form or whole
- How does the brain transform a variety of
independent stimuli into a complete
representation? - Rehfeldt is also a German word
88Organizing principles of Gestalt psychology
891.) Figure and Ground
- Figure in front of ground
- Helps you recognize that objects (like faces) are
separate from their surroundings - Which is figure and which is ground?
902. Grouping
- Proximity
- Similarity
- Continuity
- Connectedness
- Closure
913. Depth Perception
- Ability to see objects in three dimensions
- Binocular cues two eyes
- Retinal disparity each eye, and therefore each
retina, receives a slightly different image - 3D movies
- Convergence
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93- Monocular cues
- Relative size- object that casts the smaller
retinal image is farther away (if similar in
size) - Relative clarity hazy objects look farther away
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95- Relative height objects higher in our field of
view are perceived as farther away
96- Interposition if one object blocks our view of
another, we see it as closer - Texture gradient a change from distinct texture
to indistinct texture implies distance
97- Relative motion
- Linear perspective
- Light and Shadow
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994. Motion Perception
100Apparent Motion
Phi Phenomenon When lights flash at a certain
speed they tend to present illusions of motion.
Neon signs use this principle to create motion
perception.
Two lights flashing one after the other.
One light jumping from one point to another
Illusion of motion.
101Perceptual Constancy
- Shape and size
- Size and distance
- Lightness
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105- Perceptual adaptation
- Perceptual set readiness to detect a particular
stimulus in a given situation (home alone?) - FOX OWL SNAKE TURKEY DEER B?ll
- BOB RAY DAVE STEVE TOM B?LL
106- TIME FLIES I CANT THEYRE TOO FAST
107- Sally announces to her kindergarten classmates
that today is the birthday of both her father and
her grandfather. Both are exactly 50. Her teacher
says thats impossible. Is Sally right?
108Which monster is bigger?
109- Look at the Ponzo Illusions below.
Which Line is longer?
Which Elephant is Biggest?
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112ESP
- Extrasensory Perception
- Telepathy mind to mind communication
- Clairvoyance ability to sense distant events
- Precognition telling the future
- Psychokinesis ability to move objects with your
mind
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116- If your eyes follow the movement of the rotating
pink dot, you will only see one color, pink. If
you stare at the black in the center, the
moving dot turns to green. Now, concentrate on
the black in the center of the picture. After a
short period of time, all the pink dots will
slowly disappear, and you will only see a green
dot rotating if you're lucky! It's amazing how
our brain works. There really is no green dot,
and the pink ones really dont disappear. This
should be proof enough, we don't always see what
we think we see.
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