VISUALIZING
Prepared By:
Ralph Hofmann, Durham College
Chapter 4:
Sensation and
Perception
Media Enhanced PowerPoint  Presentation
Copyright © 2013 John Wiley & Sons, Canada Ltd
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Lecture Overview
•
•
•
•
What is Sensation?
How We See and Hear
The Other Senses
The Magic of Perception
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W h a t i s
S e n s a t i o n ?
LEARNING OBJECTIVES:
1. Describe how raw sensory stimuli are
translated and conveyed to the brain.
2. Explain how the study of thresholds
helps to explain sensation.
3. Describe why adapting to sensory
stimuli provides an evolutionary
advantage.
4. Identify the factors that govern pain
perception.
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What is Sensation
• Sensation
– Process of receiving,
translating, and
transmitting raw sensory
information from the
external and internal
environments to the
brain
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Detecting and
Translating Information
• Sense organs contain receptors which
receive and process sensory information
from the environment
• Each respond to a distinct stimulus
• Species evolve a range of sensory receptors
uniquely adapted to their environment
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Detecting and
Translating Information
• Sensory transduction
– The process by which a physical stimulus is
converted to a neural impulse
• Labelled lines
– The way that the brain interprets the type of
sensory information based on its neural origin
in the body and its destination in the brain
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Sensory Processing
within the Brain
• Neural impulses gained
through the senses are
sent to various parts of
the brain
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Adaptation
• Sensory adaptation
– Repeated or constant stimulation decreases
the number of sensory messages sent to the
brain from sense receptors
• Evolutionary perspective
– Helps brain cope with an overwhelming
amount of sensory information
– Allows brain time to pay attention to change
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Measuring the Senses
• Psychophysics
– Study of the relationship between real world
events and our psychological experiences of
them
– Study how the strength or intensity of
stimulation affect us
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Measuring the Senses
• Testing for hearing loss
– Tone generator produces sounds of differing
pitches/intensities
– Subject indicates the earliest point at which
they hear the tone (absolute threshold)
– Gradually change volume until subject notices
a difference (difference threshold)
– Compare thresholds to normal hearing
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Adaptation
• Some senses like smell and touch adapt
quickly
• We never really adapt to visual or
extremely intense stimuli
– e.g. odour of ammonia or pain of a bad burn
• Facilitates learned avoidance and
encourages protective self-care
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Measuring the Senses
• Absolute threshold
– Smallest amount of a stimulus we can detect
• Difference threshold
– Minimal difference needed to detect a stimulus
change; also called the just noticeable
difference (JND)
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Pain
• Initially detected by noniceptors
– Information sent via two different paths, signaling
two types of pain
• Sharp, localized pain
– Travels via myelinated fibres to spinal cord andf
then to thalamus and cortex
– Allows organism to respond rapidly and reflexively
• Dull, throbbing or burning pain
– Slower unmyelinated travels via spinal cord to
brain and interacts with limbic system
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Pain
• Significant psychological component to pain
– Perception and reaction to pain influenced by
age, sex, fatigue and emotions
• Pituitary and hypothalamus produce
endorphins
– Natural pain killers
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Gate – Control Theory
• Experience of pain depends partly on
whether the neural message can get past
the “gatekeeper” in the spinal cord
• When injury occurs:
– Neural message travels via both pathways
through open gate to brain
– Result is the subjective experience of pain
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Gate – Control Theory
• Messages from the
brain can close the gate
• Prevents subjective
experience of pain
• Triggered by
psychological factors
• Allows athletes, soldiers
to perform in spite of
injury and pain
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Gate – Control Theory
• Research shows that the pain gate may be
chemically controlled
– Opened by substance P
– Closed by endorphins
• When sensory pain is interrupted
– Brain can generate pain and other sensation
– e.g. Phantom limb pain
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Mirror Therapy
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H o w W e S e e
a n d H e a r
LEARNING OBJECTIVES:
1.
2.
3.
4.
Identify the three major characteristics of
light and sound waves.
Explain how the eye captures and focuses
light energy and how the eye converts light
energy into neural signals.
Describe the path that sound waves take in
the ear.
Summarize the two theories that explain how
distinguish among different pitches.
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Waves of Light and
Sound
• Light waves
– Packets of electromagnetic energy
– Different waves on the electromagnetic
spectrum have different wavelengths
• Sound waves
– Caused by air molecules moving in a particular
wave pattern
– Vibrating object (vocal cords, etc)compress
then decompress air molecules
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Properties of Vision
and Hearing
• Both light and sound waves vary in
– Wavelength
– Amplitude (height)
– Frequency
– Range
• Each has a distinct effect on vision and
hearing
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Properties of Vision
and Hearing
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Light Waves
• Wavelength
– Determines frequency (hue and colour)
• Amplitude
– Determines brightness and intensity
• Complexity
– Determines saturation
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The Electromagnetic
Spectrum
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Vision
• Most structures of the eye involved in
– Capturing and focusing light
– Converts it to neural signals
• Small abnormalities in the eye alterations in
focus
– Focus in front of retina
• Myopia or near sightedness
– Focus behind retina
• Hyperopia or farsightedness
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How The Eye Sees
• Light is captured and focused through the cornea,
lens and pupils onto the retina
• In the retina, light waves are changed into neural
signals
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How the Eye Sees
• Receptors for
vision (rods and
cones) are located
in the retina
• The fovea, a pit
filled with cones, is
responsible for our
sharpest vision
• The blind spot,
near the fovea, has
no visual receptors
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Hearing
• Mechanisms to distinguish sounds vary
with pitch
• Place theory
– High frequency sound waves maximally
stimulate hair cells along the basilar membrane
• Frequency theory
– Low pitched sounds cause hair cells to fire
neural messages at the same frequency as the
sound
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Sound Waves
• Wavelength
– Determines pitch (highness or lowness)
• Amplitude
– Determines loudness (intensity of the sound)
• Complexity (range)
– Determines timbre
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Hearing
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How The Ear Hears
• Structures of
the outer and
middle ear
gather/focus
sound waves
• Conducting to
the cochlea
• Receptors for
hearing are
hair cells in
the cochlea
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Hearing Loss
• Conduction/middle ear deafness
– Deafness that results from problems with the
mechanical system that conducts sound waves
to the inner ear
– Most is temporary
• Nerve/inner ear deafness
– Results from damage to the cochlea, hair cells
or auditory nerve
– Almost always irreversible
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Hearing Loss
• The loudness of a sound
is measured in decibels
• Hearing loss can be
avoided by:
– Avoiding loud noise
– Wearing earplugs when
it is unavoidable
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O u r O t h e r
S e n s e s
LEARNING OBJECTIVES:
1. Explain the importance of smell and
taste to survival.
2. Describe how the information
contained in odour molecules
reaches the brain.
3. Identify the locations for the body
senses.
4. Explain the role of our vestibular and
kinesthetic senses.
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Smell and Taste
•
•
•
•
Sometimes referred to as chemical senses
Both involve chemoreceptors
Located near each other and often interact
Sometimes difficult to differentiate
between the senses
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Smell
• Oldest and most universal sense
• More than 1000 types of olfactory
receptors
• Tends to be less sensitive
• Utilized to detect food and communication
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How The Nose Smells
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Smell
• Gustation might be the least critical sense
• Likely contributed the most to our
evolutionary survival
• Most food and taste preferences are
learned
– Childhood experiences
– Cultural influences
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Taste
• Food and liquid
dissolved in saliva
• Flows over papillae and
into pores
• Taste buds contain
receptors to taste
• Trigger neural impulses
to cortex via thalamus
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The Body Senses
• Senses that tell the brain:
– How the body is oriented
– Where and how the body is moving
– What is touched or touches the body
• Includes:
– Skin senses
– Vestibular sense
– Kinesthetic sense
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Skin Senses
• Skin sensitive to touch (pressure)
temperature and pain
• Concentration and depth of receptors for
each stimuli vary
– e.g. touch receptors most concentrated on the
face, hands, genitals
• Some receptors respond to more than one
stimuli
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Vestibular Sense
• Responsible for balance
• When the head moves:
– Liquid in the semicircular canals move bending
hair receptors
– Vestibular sacs at the end of the canals reorient
– Information then converted to neural impulses
to the brain
• Motion sickness occurs when the vestibular
sense becomes confused
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Kinesthesia
• Provides the brain with
information about body
posture, orientation
and movement
• Receptors found in
muscles, joints and
tendons
– Informs brain of which
muscles are
contracted/relaxed,
weight distribution, etc
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T h e M a g i c o f
P e r c e p t i o n
LEARNING OBJECTIVES:
1. Describe the relationship among
selective attention, feature
detectors, and habituation.
2. Summarize the factors involved in
perceptual interpretation.
3. Describe the limitations of
subliminal perception.
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Perception
• The process of selecting, organizing and
interpreting sensory data
• Three basic perceptual processes:
– Selection: attending to some sensory stimuli
while ignoring others
– Organization: assembling information into
patterns that help us understand the world
– Interpretation: how the brain explains
sensations
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Optical Illusions
• Optical illusion
– False or misleading perceptions
– Produced by either interpretation error or physical
distortion
• Help scientists study normal perception
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Selecting and
Extracting Information
• Three major factors help us select and focus
on specific stimuli and ignore others
– Selective attention
– Feature detectors
– Habituation
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Selective Attention
• The ability to filter out
distractions and
attending only to
important sensory
information
– Brain picks out
information that is
important and relevant
and ignores the rest
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Feature Detectors
• Specialized cells in the brain that respond
only to certain sensory stimuli
– There are feature detectors for all sorts of
visual stimuli
– Lines, edges, shapes and movement
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Habituation
• Tendency to ignore
environmental factors
that remain constant
– Brain is prewired to pay
more attention to
changes in the
environment than to
stimuli that remain
constant
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Organization
• Raw sensory information must be organized
in a meaningful way to be functional and
useful
• We organize sensory information in terms
of:
– Form
– Constancy
– Depth
– Colour
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Form Perception
• Gestalt psychologists were the first to study
how the brain organizes information into
gestalt (form or whole)
– Figure and ground
– Proximity
– Continuity
– Closure
– Similarity
– Contiguity
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Gestalt Laws of
Organization
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Reversible and
Impossible Figures
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Perceptual Constancy
• Perceiving the
environment as
remaining the same
even with changes in
sensory input
• Four constancies:
–
–
–
–
Size
Shape
Colour
Brightness
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Perceptual Constancy
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Depth Perception
• Ability to perceive three
dimensional space and
accurately judge
distance
– Primarily relies on
experience
– Relies on monocular and
binocular cues
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Binocular Depth Cues
• Relies on having two forward facing eyes
• Inadequate in judging distances longer than a
football field
• Retinal disparity
– Different images fall on each retina
– Brain fuses multiple images into one stereoscopic
vision
• Convergence
– The closer an object looks the more our eyes turn
inward
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Binocular Depth Cues
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Monocular Depth Cues
• Available separately to each eye
• Linear perspective
– As they recede in distance, parallel lines
converge on each other
• Interposition
– Objects that obscure or overlap each other are
perceived as closer
• Relative size
– Close objects cast a larger retinal image
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Monocular Depth Cues
• Texture gradient
– Nearer objects have a coarser and more
distinct texture
• Aerial perspective
– Distant object appear hazy and blurred
because of intervening atmospheric dust or
haze
• Light and shadow
– Brighter objects are percieved as closer
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Monocular Depth Cues
• Relative height
– Objects positioned higher in our field of vision are
perceived as farther away
• Accommodation of the lens
– Muscles adjust the shape of the lens as objects
move closer
• Motion parallax
– When we are moving, close object appear to whiz
by whereas farther objects appear to move more
slowly
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Monocular Depth Cues
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Colour Perception
Theories
• Trichromatic theory
– Colour perception results from mixing three
distinct colour systems
– Red, green, blue
• Opponent process theory
– Colour perception results from three systems
of colour opposites
– Blue-yellow, red-green, black-white
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Colour After - Effects
• Explainable by the opponent process
theory
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Colour – Deficient
Vision
• Most people perceive
three colours
• A small proportion can
only perceive two
• People with a red-green
colour-deficiency
cannot see the green
number in the diagram
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Interpretation
• Final stage in perception
• Interpretation involves four major factors:
– Perceptual adaptation
– Perceptual set
– Frame of reference
– Bottom-up versus top-down processing
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Interpretation
• Perceptual adaptation
– Ability to adapt to new stimuli and create
coherence
• Perceptual set
– Readiness to perceive things a certain way
• Frame of reference
– Perceptions depend on the context of the
situation
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Perceptual Set
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Interpretation
• Bottom-up processing
– Receive information that works its way up to
the top levels of perceptual processing
• Top-down processing
– Previous experience, thoughts, expectations,
etc. begins with higher level processing and
works down to sensory
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Science and ESP
• Extrasensory perception
– The concept that some people can perceive
things that cannot be perceived by normal
senses
• Scientific and causal explanations lack
stability and replication
• May be just an example of motivation and
interests affecting perception
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Subliminal Perception
• Perception without conscious awareness
• Little or no evidence that it leads to
subliminal persuasion
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Multimedia
Web Links
Science: Human Body & Mind
Nervous System
Brain Controls Pain
Scientists are finding that it truly is the brain that
decides what is or is not painful. As this ScienCentral
News video explains, scientists are also finding that
there may be a way to teach people to train their
brain to better handle pain.
Science: Human Body & Mind
Nervous System – Sight
Exploratorium
Cow’s Eye Dissection
Eye Institution
Welcome to the University of Ottawa Eye Institute of
The Ottawa Hospital. We are a world class facility
recognized internationally for excellence in patient
eye care, research and teaching in the field of
ophthalmology.
Seeing more than your eye does
Most people (even many who work on the brain)
assume that what you see is pretty much what your
eye sees and reports to your brain. In fact, your brain
adds very substantially to the report it gets from
your eye, so that a lot of what you see is actually
"made up" by the brain.
Artificial Eye
A camera that transmits pictures into the brain, as
this ScienCentral News video explains, is giving some
people suffering from blindness the chance at partial
eyesight again.
Exploratorium
This dynamic presentation digitally recreates three
auditory illusions found at the Exploratorium Science
Museum in San Francisco, California.
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Multimedia
Web Links
Anatomy of the ear
Sound is produced when an object vibrates. These
vibrations, in turn, cause the surrounding air
molecules to vibrate. The vibration spreads out from
the object in waves, much like ripples in a pond after
a stone has been thrown in.
Science: Human Body & Mind
Nervous System – Hearing
How Hearing Works
Your ears are extraordinary organs. They pick up all
the sounds around you and then translate this
information into a form your brain can understand.
One of the most remarkable things about this
process is that it is completely mechanical. Your
sense of smell, taste and vision all involve chemical
reactions, but your hearing system is based solely on
physical movement.
Super Snout
Dogs are naturally nosy creatures, so chemists have
been trying to find a way to create a device as
sensitive as their snouts. As this ScienCentral News
video reports, they're coming close.
Science: Human Body & Mind
Nervous System – Smell
How does the sense of smell work?
Smell is a very direct sense. In order for you to smell
something, molecules from that thing have to make
it to your nose. Everything you smell, therefore, is
giving off molecules -- whether it is bread in the
bakery, onions, perfume, a piece of fruit or whatever.
Those molecules are generally light, volatile (easy to
evaporate) chemicals that float through the air into
your nose. A piece of steel has no smell because
nothing evaporates from it -- steel is a non-volatile
solid.
Copyright © 2013 John Wiley & Sons, Canada Ltd
75
Multimedia
Web Links
‘Supertasters’ diet raises cancer risk
People whose genes have given them a super-sharp
sense of taste are more susceptible to colon cancer
than those with duller palates, suggests new
research.
Science: Human Body & Mind
Nervous System – Taste
Science: Human Body & Mind
Nervous System – Touch
Discovery Fit & Health
Homepage
Science: Human Body & Mind
Nervous System - Balance
MindBluff.com
The Necker Cube
101 Visual Phenomena & Optical Illusions
These pages demonstrate visual phenomena and
»optical« or »visual illusions«.
Gallery of Visual Illusions
Homepage
Colorcube
Optical Illusions presented by COLORCUBE.com!
Gestalt Principles of Perception
Gestalt theory first arose in 1890 as a reaction to the
prevalent psychological theory of the time atomism.
Jumping to Conclusions
We've carefully covered these words so you can only
see part of each letter. But try to read them anyway.
What do you think they say?
Visual Illusions – Monocular Cues
Follow the links in the table below to view graphical
images demonstrating an example or an illusion of
each monocular cue.
Interposition
Textbooks use simple images to illustrate many of
the perceptual cues that give rise to the impression
of depth.
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76
Multimedia
Web Links
After Images
Stare at the plus sign on the left for about 30
seconds. As you do this you probably will see some
colors around the blue and green circles. After about
30 seconds, shift your gaze to the plus sign on the
right. What did you see?
Bird in a Cage
Getting used to looking at one color can lead you to
perceive an entirely different color.
Mindbluff.com
Subliminal Words
Mindbluff.com
Subliminal Sentence
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Multimedia
Videos
Virtual Reality and Vision (2:03)
Its a problem most of us never think about, but
scientists have long wanted to know how we manage
to walk around without running into things.
Hearing Screenings (1:47)
As many as one in one thousand babies born
completely deaf every year. Another two or three per
thousand have some hearing loss. As this
ScienCentral News video reports, one researcher is
calling for hearing screenings for newborns because
the earlier hearing loss is discovered, the better.
Super Smellers (1:18)
Why do nearly half of all people over age 65
experience some deree of smell loss? As this
ScienCentral News video reports, some supersmelling mice might hold the answer.
Smart Nose (1:33)
Do you smell with your nose or your brain?
The Nose Knows (2:10)
If you’re like most people, you’re probably looking
forward to the tastes of special foods that this time
of year brings. But how much of that eggnog or roast
turkey flavor actually comes from taste? It may not
be as much as we think.
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78
Multimedia
Animations
How We See and Hear
How do our bodies know where to move when
something is coming at us?
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79
Copyright
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