1 Psychophysics • 2) Perceptual Expectancy - how we perceive the world is a function of our past experiences, culture, and biological make-up. you may look at a painting and not really understand the message the artist is trying to convey. But, if someone tells you about it, you might begin to see things in the painting that you were unable to see before. 24 I want you to take a moment and think about all the animals you may encounter at the petting zoo or on a farm. Just visualize these things. When I show you a picture I want you to quickly write down what you see. Do not discuss this with anyone. 25 26 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. More examples of Sensory Adaptation • humming of the projector • AC noise in background • Weight of your shirt • Socks/shoes feeling a little uncomfortable – Sensory adaption- allow us to shift attention to other things – Even the constant quivering of our eyes minimize when we focus on something 27 28 Now you see, now you don’t 29 Transduction In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses.
Transcript
1
Psychophysics
• 2) Perceptual Expectancy - how we perceive the
world is a function of our past experiences,
culture, and biological make-up. you may look at
a painting and not really understand the
message the artist is trying to convey. But, if
someone tells you about it, you might begin to
see things in the painting that you were unable
to see before.
24
I want you to take a moment and think about all the
animals you may encounter at the petting zoo or on a
farm. Just visualize these things. When I show you a
picture I want you to quickly write down what you see.
Do not discuss this with anyone.
25
26
Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Put a band aid on your arm and after awhileyou don’t sense it.
More examples of Sensory
Adaptation• humming of the projector
• AC noise in background
• Weight of your shirt
• Socks/shoes feeling a little uncomfortable
– Sensory adaption- allow us to shift attention to
other things
– Even the constant quivering of our eyes
minimize when we focus on something
27
28
Now you see, now you don’t
29
Transduction
In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses.
2
30
Vision
31
VisibleSpectrum
The Stimulus Input: Light Energy
Both
Photo
s: T
hom
as
Eis
ner
Pulses of
electromagnetic
energy
32
2 Physical Characteristics of Lightthat determines our sensory experience of
them:
1. Wavelength (hue/color)
2. Intensity (brightness)
33
Wavelength (Hue)
Hue (color) is the dimension of
color determined by the
wavelength of the light.
Wavelength is the distance from the peak of one wave to the peak of the
next.
34
Wavelength (Hue)
Different wavelengths of light resultin different colors.
400 nm 700 nmLong wavelengthsShort wavelengths
Violet Indigo Blue Green Yellow Orange Red
35
Intensity (Brightness)
Intensity:Amount of energy in a
wave determined by the amplitude. It is related to
perceived brightness.
3
36
Intensity (Brightness)
Blue color with varying levels of intensity.As intensity increases or decreases, blue color
looks more “washed out” or “darkened.”37
The Eye
38
Parts of the eye
1. Cornea: Transparent tissue where light enters the eye.
2. Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light.
3. Lens: Focuses the light rays on the retina.
4. Retina: Contains sensory receptors that process visual information and sends it to the brain.
39
The Lens
Lens: Transparent structure behind the
pupil that changes shape to focus images on the
retina.
Accommodation: The process by which the
eye’s lens changes shape to help focus near or far
objects on the retina.
Near and Far Sightedness
• Notice the shape of
the eye. Elongated
for nearsightedness
and shorter than
normal for far
sightedness
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• Optic nerve – the nerve which takes information to the
occipital lobe for processing
• Blind spot- you guessed it where the optic nerve leaves
your eye… no receptors, but your brain fills in the gap
• Feature Detectors – these are allow us to see specific
features…. Edges, lines, angles, and movement (pix
later)
• Hubel & Wiesel – Nobel prize winners for work on
Feature detectors in the visual cortex
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4
42
Retina
Retina: The light-sensitive inner
surface of the eye, containing receptor rods and cones in
addition to layers of other neurons
(bipolar, ganglion cells) that process
visual information.
� Cones – cluster around the Fovea
� Located near center of retina
� Allow us to see different wavelengths so we can see
fine detail and have color vision
� See in daylight or well-lit conditions
Fovea- central point in retina, where cones cluster what
we are looking @)
� Rods
� peripheral retina (location)
� detect black, white and gray
� They are more light sensitive allowing them to see
twilight or low light
Rods and cones share cells and send combined
messages thru the optic nerve which starts the
transduction process43
44
Test your Blind Spot
Use your textbook. Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At
some point the car on the right will disappear due to a blind spot.
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Photoreceptors
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969
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Bipolar & Ganglion Cells
Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which converge to form the optic nerve.
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Visual Information Processing
Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to
the visual cortex.
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48
Feature Detection
Nerve cells in the visual cortex respond to specific features, such as edges, angles, and
movement.
Don’t try this at home!
• Pac Man in the House!!!
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We create Illusory Contours
50 51
Shape Detection
Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and
houses.
Ish
ai,
Un
gerl
eid
er,
Mart
in a
nd
Haxb
y/ N
IMH
52
Visual Information Processing
Processing of several aspects of the stimulus simultaneously is called parallel processing. The
brain divides a visual scene into subdivisions such as color, depth, form, movement, etc.
53
From Sensation to Recognition
6
The colors we see
� Trichromatic (three color) Theory
� Thomas Young and Hermann von Helmholtz=
Trichromatic Theory
� Cones see colors in teams of 3 primary colors
Combine to make any color
�red
�green
�blue
�
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“The (light) rays are not colored.”
- Isaac Newton
Color does not reside in the object rather it is only
our brains interpretation from the light waves we
have taken in and processed.
Anyone dream in color???
The wavelength of light determines the color, so in
a properly functioning eye and brain, the color will
processed the same. However what we call color
shades can vary significantly
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Color Blindness
Ishihara Test
Genetic disorder in which people are blind to green or red colors. This supports the
Trichromatic theory.
Opponent Process Theory
• Ewald Hering
questioned why
those who could
not see red and
green were often
still able to see
yellow? Why does
yellow seem to be
a pure color?
• Afterimages gave him this
theory. As visual info
leaves the receptor , we
analyze it in terms of 3
sets of opponent colors:
red-green, yellow-blue,
white-black. In the retina
and thalamus, some
neurons are turned on by
red but turned off by
green. Others are turned
on by green but off by
red. 57
Afterimages
• Try the flag
exercise in your
book
• Stare at the flag for
60 seconds then
shift your eyes to
the dot in the white
space beside it.
• Afterimages are
not limited to color
vision though. You
can see after
images of
movement as well.
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Afterimages
• afterimages 2
59
• afterimages 3
7
Where are we today on vision?
• Currently most feel that there are 2 stages
of vision
• 1st Trichromatic (Young-Helmholtz)
• 2nd color is processed by nervous system
using opponent process theory en route
to our visual cortex.
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Relative luminance
61
Squares “A” and “B”
are identical in
color.
We perceive “B” as
lighter, due to the
surrounding context.
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64
Hearing
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Hearing
The Stimulus Input: Sound Waves
Sound waves are compressing and expanding air molecules.
8
66
Sound Characteristics
1. Frequency (pitch)
2. Intensity (loudness)
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The Ear
Dr. F
red
Ho
ssler/ V
isuals U
nlim
ited
68
The Ear
Outer Ear: Collects and sends sounds to the eardrum.
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, containing the cochlea, semicircular canals, and vestibular sacs.
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Cochlea
Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to
auditory signals.
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Intensity (Loudness)
Intensity (Loudness):
Amount of energy in a wave,
determined by the amplitude, relates to the perceived
loudness.
71
Loudness of Sound
70dB
120dB
Ric
hard
Kay
lin/ S
ton
e/ G
etty
Images
9
Tinnitus: Can you hear that?
72 73
Frequency (Pitch)
Frequency (pitch):The dimension of
frequency determined by the
wavelength of sound.
Wavelength: The distance from the peak of one wave to the peak of the
next.
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Localization of Sounds
Because we have two ears, sounds that reach one ear faster than the other ear cause us to
localize the sound.
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Localization of Sound
1. Intensity differences
2. Time differences
Time differences as small as 1/100,000 of a second can cause us to localize sound. The head acts as a
“shadow” or partial sound barrier.
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Touch
The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain.
Bru
ce A
yers
/ S
ton
e/
Gett
y I
mages
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Skin Senses
Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth,
cold and pain.
Burning hot
Pressure Vibration Vibration
Cold, warmth and pain
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Pain
Pain tells the body that something has gone wrong. Usually pain results from damage to the
skin and other tissues. A rare disease exists in which the afflicted person feels no pain.
Ashley Blocker (right) feels neither pain
nor extreme hot or cold.
AP
Ph
oto
/ Ste
ph
en
Mo
rton
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Biopsychosocial Influences
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Gate-Control Theory
Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that
either block pain or allow it to be sensed.G
ary
Co
mer/ P
ho
tota
keU
SA
.co
m
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Pain Control
Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise,
Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”.
Sweet Sour Salty Bitter Umami
(Fresh
Chicken)
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Sensory Interaction
When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry
interacts with its smell and its texture on the tongue to produce flavor.
Orange Juice is yummy but I don’t like oranges
I won’t let a pickle get within 5 feet of me- the smell is awful, I can almost taste it
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84
SmellLike taste, smell is a chemical sense. Odorants
enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are
many different forms of smell.
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Smell and Memories
The brain region for smell (in red) is closely
connected with the brain regions involved with memory (limbic system). That is why strong memories are
made through the sense of smell.
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Body Position and Movement
The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position.
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Whirling Dervishes Wire Walk
Bob D
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s
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Perceptual Organization
How do we form meaningful perceptions from sensory information?
We organize it. Gestalt psychologists showed that a figure formed a “whole”
different than its surroundings.
88 90
Grouping
After distinguishing the figure from the ground, our perception needs to organize the figure into
a meaningful form using grouping rules.
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Grouping & Reality
Although grouping principles usually help us construct reality, they may occasionally lead us astray.
