10/16/2015
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Sensation and Perception
Shorter wavelengths give
us “blue” experience
Longer wavelengths give
us “red” experience
Our Link With the World
Sensation: outside stimulus is detected by specialized
receptors and transduced into electrical messages to be
sent to brain
Perception: brain tries to organize, interpret & recognize
what’s being sensed
Page 96
You are responsible
for knowing the parts of
the eye and their
functions (p 94-95)
Receptors in the eye are sensitive to a small range of wavelengths
of electromagnetic energy – the “visible spectrum”
Two Kinds of
Photoreceptors:
Rods vs Cones
• ~120 million/eye
• more in periphery
• very sensitive – respond
even in dim lighting
• ~100 rods share same optic
nerve fiber to brain
• night vision
• ~6 million/eye
• most in fovea (center)region
• need bright light to work
• have more private lines to
brain- good for detail vision
or “visual acuity”
• 3 different types of cones provide color vision
Receptors are the deepest layer!!
2 Theories of Color Vision (p. 98-99)
Proposed in 1800’s
• Trichromatic Theory – 3 types of color (R,G,B) receptors
work together to represent all colors of the spectrum.
• Opponent Process Theory – cells in the visual pathway
receive input about pairs of colors (R-G or B-Y). One
color makes them fire faster, the other makes them fire
slower.
Color “Opposites” on the
Color Wheel
• Now have actual
evidence for 3
Cones
different types of
cones in retina,
absorbing different
ranges of
wavelengths
• Supports
Trichromatic
Theory
• Some people don’t
have all types of
cones
“Afterimages” of strong
visual stimuli are in
opposite colors
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What Do You See?
Tests for Normal Color Vision
Thinking About Sound Waves
• Inability to distinguish red from green is the most common type of
“color blindness”
Waves vary in how many molecules are moved
(amplitude) and how many waves per second (frequency)
Page 100 in book
Measured in decibels
The Ear
Fluid Motion in Cochlea
You are
responsible for
knowing the
parts of the ear
and their
functions (p
127)
• https://www.youtube.com/watch?v=flIAxGsV1q0
A diagrammatic tour through the ear
• http://www.youtube.com/watch?v=U_HUgzhmq4
U Real life views of the auditory structures
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How Do We Hear Different Pitches (20-20,000) Hz?
Audition
(Hearing)
• ~ 15,000 auditory receptors called hair cells lined up
on the long basilar membrane inside each cochlea
• Movements of membrane as fluid waves ripple thru
cochlea result in bending of hair cells which triggers
their electrical messages
• Frequency theory – for low frequency deep pitches the
auditory nerve fires at the same freq as the pitch we are
hearing, telling the brain the pitch
• BUT – nerves can’t fire faster than 1000/sec so this only
works for low freq sounds
• Place Theory - for higher pitches, diff. pitches maximally
stimulate different places along the basilar membrane.
• This “place” in the cochlea
tells
the brain the pitch.
• Visualize how different pitches stimulate different spots
• https://www.youtube.com/watch?v=dyenMluFaUw
Loud Sounds“Trample” Hair Cells
• Repeated exposure can cause
permanent damage
• Researchers are really worried
about this “ear-bud” generation
• Expect more rapid aging of your
ears if they are abused
• Test your hearing – have you
already lost your upper range?
Types of Deafness (p. 115)
• Conduction Deafness – auditory stimulus does not pass
normally through auditory canal, ear drum or middle
ear.
• Neural Deafness – deafness due to damage to hair cells
or auditory nerve.
http://www.youtube.com/watch?v=Ire
wnzQYrPI
https://www.youtube.com/watch?v=VxcbppCX6Rk
http://www.youtube.com/watch?v=Irewnz
QYrPI
2 Chemical Senses
Fungiform Papillae
(bumps on tongue)
• Taste
• Smell (Olfaction)
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Olfactory Receptors Located High
Up in Nasal Passages
Tastes Buds on Sides of Papillae
We only have taste receptors for these qualities: sweet, sour,
salty, bitter, and “umami” (meaty flavor). Most of what we call
“flavors” (orange, grape, bubble gum, etc) depend on smell
more than taste.
•
These receptors also have cilia – in this case to be exposed to odorous molecules in the air we sniff.
Olfaction (Smell)
Smell
Olfactory receptors
send their axons
thru the skull to
brain. This
arrangement puts
them at risk of
being torn off of
brain in a head
injury situation.
Olfaction
• About 1 in 100 suffer serious anosmia (loss of sense of
smell); many more have partial anosmias where they lack
the ability to detect certain odors.
• 75-90% of those with Alzheimer’s have decreased olfactory
sensitivity (may be useful in early diagnosis)
• Women have a better sense of smell than men, with peak
olfaction at time of ovulation, and may use olfaction when
choosing mates.
• Humans may not think that their olfactory sense is
very sensitive or important.
• But we have 6-10 million olfactory receptors at the
top of each nostril in humans (there are about 10-20
times as many in dogs)
• More than 1000 different types of olfactory receptors
to detect different shaped molecules!
• Some of the impact of olfactory stimuli may be at the
unconscious level via pheromones that affect our
physiology & behavior.
Pheromones
• Pheromone: chemical signal from 1 member of species which affects
biology and/or behavior of another member of species.
• Female mice housed together frequently stop having an estrus cycle.
The presence or the smell of a mature male induces ovulation and a
normal estrus cycle.
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Menstrual
Synchrony: A
Pheromone
Example in
Humans
Gestalt Psychology
• Studied what organizing principles our perceptual system uses to turn
a million pixels of visual input into meaningful whole figures
• Women living together not on hormonal birth control
tend to have their cycles come into synchrony
because of pheromones.
The Perception Regions
of Brain Must:
Select what sensory input to focus attention on
Organize the input from millions of receptors (“bottom–up
processing”)
Interpret/recognize input in terms of your past
experience, expectancies, context (“top-down processing”)
This means that perception is very individualized.
What you experience is NOT just the result of sensory input.
Figure/Ground
Multiple cues
(brightness, shading,
borders, decoration) to
identify the vase as the
figure against the dark
background.
Perceptual Processing Tasks
• Pick out the figure or foreground from the background
• Identify patterns, continuous lines, what things go
together, the “whole” or the “Gestalt”
• Match input to your memories of past sensory
experiences (recognition)
• Maintain that recognition even if angle of view, lighting, or
distance changes (perceptual constancies)
• Distinguish depth, distance, 3-dimensions
Face-Vase Illusion –
A Reversible Figure
(not clear what is figure vs ground)
Without enough cues,
figure/ground task
becomes more difficult.
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Necker Cube –
Another Reversible Figure
• Is the red dot at the front of the cube or the back
corner of the cube? Can you make it switch?
Perception Depends on Context, Past
Experience, Expectations or
“Perceptual Set”
Perception Depends on Context, Past Experience,
Expectations or “Perceptual Set”: What if we
change the “context”?
An expectations example:
A context examplewhat is the middle
stimulus?
An Auditory Example of Top-Down Processing
Influencing Perception
• “Backmasking” – are there hidden messages in a piece of music
played backwards?
• http://www.albinoblacksheep.com/flash/queen
• http://www.youtube.com/wat
ch?v=BnKV4jGhec&feature=related
Monocular (“one eye”) Cues
or “Artist’s Cues” for Depth
• Relative Height
• Relative Size
• Texture Gradient
• Linear Perspective
• Aerial or Atmospheric Perspective
• Interposition
• Motion Parallax or Relative Motion
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Relative Size & Height Cues
Parallel lines appear to converge on horizon)
Interposition
Cues
(one thing
blocks view
of another)
Texture gradient cues
Motion Parallax
Distant things are fuzzier, less distinct
Closer objects appear to pass by quickly
We also have internal cues for depth
that come from having 2 eyes
Binocular (2 eye) Cues
• Convergence of Eyes
• As objects get close to us, our eyes point inward. Perception system uses this
muscle feedback as depth cue.
• Retinal or Binocular Disparity
• Difference between what right eye sees and what left eye sees is used to
determine depth perception and seeing objects as 3 dimensional.
Perceptual Constancy
• We perceive that objects remain constant, even
though the retinal image continually varies as we or
the object moves or the environmental conditions
(like lighting) change.
• Size constancy(as object moves closer or farther)
• Shape constancy (as our angle of viewing changes)
• Color constancy (as lighting changes)
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Manipulating Your Perceptions: Illusions
(when the cues we normally use
deceive us)
Impossible Trident
Impossible Triangle
Ames Room
http://www.youtube.com/watch?v=5ic7QGjGEX8
http://www.youtube.com/watch?v=Ttd0YjXF0no
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Because of size constancy and depth perception we are
not bothered by the difference in the size of the guy in the
white shirt.
• As long as I
don’t
change his
position
You Can Recognizes These
As Faces Even When Upside Down
But while getting the “Gestalt” you missed
these details:
Do You Know What Each of These
Researchers Did?
• Pavlov
• Watson
• Thorndike
• Skinner
• Bandura
• Tolman
• Kohler
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