Sensation and Perception
psyc 320
Takashi Yamauchi
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Ch 1
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Sensation & Perception
• Ch. 1: Introduction to perception
• Main topics
– Perceptual processes
– How to study perception
– How to measure perception
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• Sensation & Perception
• How is this course different from other
psychology courses?
–learn sensation & perception
–Some very basic form of mind (sensing & perceiving)
–Deal with fundamental principles of psychology
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3
Questions:
• What is perception?
Perception is about perceiving.
What is perceiving?
What do we do when we perceive?
We see, smell, hear, feel, taste, …
Ch 1
4
What tools do we have for perceiving?
• Eyes, ears, nose, tongue, skin,
– eyes  see,
– ears  hear,
– nose  smell,
– tongue  taste,
– skin  feel (temperature)
Ch 1
– skin  feel (touch)
5
What do eyes, a nose, ears, a
tongue, and skin do?
•
•
•
•
•
Eye:
Ear:
Nose:
Tongue:
Skin:
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What does the eye do?
• Eye:
Seeing,
yes but what is seeing?
– detecting light
What is light?
electromagnetic energy
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What is electromagnetic energy?
• Electro + magnetic + energy =
electromagnetic energy
• Electromagnetic energy is a stream of
photons.
– www.wikipedia.org
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What are photons?
• They are massless particles each traveling in a
wave-like pattern and moving at the speed of light.
• The smallest (quantum) unit of
light/electromagnetic energy.
• It is the carrier of electromagnetic radiation of all
wavelengths
– such as gamma rays, X-rays, ultraviolet light, visible
light, infrared light, microwaves, and radio waves.
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So what is “seeing”?
• Detecting some form of the movement of
photons (electromagnetic radiation).
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What does the ear do?
Hears sound
What is sound?
the vibration of air.
What is the vibration of air?
Where do they come from?
Air moves when something else moves
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What does the nose do?
• Nose:
is for smelling
–Where does smelling come from?
–Smelling is a “sensation caused by
odorant molecules dissolved in air.”
(wikipedia.org)
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Odorant molecules? What are they?
• Odorant (aroma compound)
•  chemical compound (e.g., H2O; a
chemical substance of two or more different
chemical elements.)
• Where do they come from?
– Organic compounds  foods, flowers,
– Inorganic compounds  ammonia,…
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Taste
• How do we get that?
– From our tongues.
• Where do we get that?
– From foods we eat.
– From specific chemicals.
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What does the skin do?
• Detect temperature:
• What is temperature?
• It is about how hot or cold something is.
• How does something get hot or cold?
• Temperature is the result of the motion of particles
which make up a substance.
• Temperature increases as the energy of this motion
increases. (wikipedia)
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What does the skin do?
feels touching
–  It responds to mechanical stimulation or
pressure
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So, what is perception?
• Perception is a system that tells us
about an environment.
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Eye, ear, nose, tongue & skin
• They are sensors.
• They are detecting some kind of changes in
an environment.
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So, studying perception we need
to study
•
•
•
•
•
How the eye works,
How the ear works,
How the nose works,
How the tongue works, and
How the skin works
• Is that all?
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What tools do we have for
perceiving?
• Eyes, ears, nose, tongue, skin,
– Eyes  see, ears  hear, nose  smell,
– tongue  taste, skin  feel
• Are these all?
• NO!
 Brain (not Bryan)
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The brain is the locus of
perception
• the study of perception entails the study of
the brain and behavior.
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A quick demonstration
• Tell me what you see.
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(A)
(B)
(A)
(B)
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Visual Illusions
• Why does this happen?
• Tell me what these illusions teach us.
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What is perception?
• Perception involves:
– Detecting the information in the environment.
– Sending the information to the brain, and
interpreting it.
• Perception is about
– Detecting and interpreting
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Let’s have some break.
• Listen to music
• See a painting
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Paul Klee: Golden fish
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Ch 1 Parnassum
Paul Klee: Ad
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Ch 1
Anselm Kiefer: Nuremberg
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Henri Rousseau: The Dream
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What’s going on?
• Perception is about detecting, but also more
than detecting.
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What’s going on when we see the
pictures?
• When we listen to beautiful music, we often
see a picture.
• When we see a beautiful picture, we hear
music. How come?
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How come?
–Different types of physical information (air
vibration, light energy) are translated into a
common language in the brain
–  neural information
Environmental Stimuli (e.g., light energy)
Transduction
Neural Processing
Perception
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Key points:
• Perception is about finding out what is going on in
an environment.
• Perceptual organs (eyes, ears, nose, skin, a tongue)
are basically detectors (sensors)
• Perception requires transforming physical
information (e.g., light) into neural information.
• Perception also involves “interpretation,” which is
carried out by the brain.
Ch 1
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Studying perception
• How perceptual detectors work.
• How physical information is transformed
(e.g., light) into neural information.
• How neural information is processed in the
brain.
• How neural information is interpreted and
triggers a specific form of perception.
Ch 1
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How come?
–Different types of physical information
(air vibration, light energy) are transformed
into a common neural language in the brain
–  neural information
Environmental Stimuli (e.g., light energy)
Transduction
Neural Processing
Perception
Ch 1
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Demonstration (attention &
perception)
• An interaction between
– attention and perception
– cognition and perception
• Tell me what you see.
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•
•
•
•
•
•
•
•
•
Tired
Old
Sick
Dark
Slow
Heavy
Hospital
ugly
death
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•
•
•
•
•
•
•
•
•
Beautiful
Young
Fresh
Fast
Energy
Juicy
Clean
cheerful
Vigorous
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Demonstration (knowledge and
perception)
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What did you see?
• What does this tell?
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Perceptual process
• Perception is the end result of complex
processes.
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Why study perception?
• If the doors of perception were to be
cleaned, man would see everything as it
truly is…..Infinite.
– William Blake
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How to approach the study of
perception
• Levels of analysis
– Psychophysical level of analysis
– Physiological level of analysis
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Measuring Perception
• Psychophysical level of analysis
– Description
• Phenomenological method
• E.g., Let a person describe what they see
– Recognition
– Detection
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• Detection
– Absolute threshold
• is the smallest amount of stimulus energy
necessary to detect a stimulus.
E.g., eye exam
– Difference threshold
• is the smallest difference between two
stimuli that a person can detect.
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Demonstration
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Demonstration: Measuring
weight
• DL (difference threshold) gets larger as the
standard stimulus gets larger.
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Demonstration
• Color, line, length
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The impact of standard stimuli
• DL (difference threshold) gets larger as the
standard stimulus gets larger.
• Weber’s law
DL/S=K
• DL: difference threshold
• S: standard stimulus
• K: constant
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Weber’s law
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Question:
• With a standard stimulus 1 kg, John’s
difference threshold was 0.25kg. With a
standard stimulus 10kg, what would be
John’s difference threshold?
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Question:
• With a standard stimulus 1 kg, John’s
difference threshold was 0.25kg. With a
standard stimulus 10kg, what would be
John’s difference threshold?
DL/S=K
DL/S=K
•DL: 0.25
•DL: ?
•S: 1
•S: 10
•K: 0.25
Ch 1
•K:
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Magnitude estimation
• Assign a value to a standard stimulus
• The subject estimates the value of a target
stimulus.
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Magnitude estimation
Standard:
== 10
Standard:
== 100
Target: == ?
Target: == ?
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Standard:
== 100
Target: == ?
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Standard:
== 100
Target: == ?
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Steven’s power law
P  KS
n
• S is the physical magnitude
of a target that you are
estimating.
• P is your estimation
• K is some value (constant)
• n is some value
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Magnitude estimation
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Ch 1
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Steven’s power law
P  KS
n
• S is the physical
magnitude of a target
that you are
estimating.
• P is your estimation
• K is some value
(constant)
• n is some value
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Experiment (you are estimating the
length of lines)
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Target = ?
Standard = 100
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Your estimations
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P  KS n
P = S raised to the n-th power
P: your estimation
S: stimulus intensity
n: some value =0.33
K: some value (constant) = 21.5
Estimating the length of stimuli
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Your estimations
Target
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0
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Ch 150
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Physical magnitudes
200
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Experiment (you are estimating the
intensity of electric shock)
Standard =
100
Target = ?
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Your estimations
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P: your estimation
P  KS
n
S: stimulus intensity
n: some value =1.5
K: some value (constant) = 0.1
Estimating the intensity of electric shock
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Your estimations
Target
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0
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Physcial magnitude
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Your estimations
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280
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200
180
160
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100
80
60
40
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0
Estimating
electric shock
Estimating the
length of lines
0
50
100
150
Ch 1
Physical
magnitudes
200
250
87
Steven’s power law
P  KS
n
• S is the physical
magnitude of a target
that you are
estimating.
• P is your estimation
• K is some value
(constant)
• n is some value
Ch 1
88
Threshold
• Absolute threshold
• Difference threshold
Ch 1
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Difference threshold
• Weber’s law
• Stevens’s law
Ch 1
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