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Sensation and Perception

Psyc 615

Takashi Yamauchi© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)

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Questions:

• What is perception?

Perception is about perceiving.

What is perceiving?

What do we do when we perceive?

We see, smell, hear, feel, taste, …

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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:

– detecting light

Seeing,

yes but what is seeing?

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.

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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 the movement of photons (electromagnetic radiation).

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What does the ear do?

Hears a 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.” (Wikipeida.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 goes up or down due to the motion of

particles. • 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

• To study perception, we have to 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

Ch 1 26Paul Klee: Ad Parnassum

Ch 1 27Anselm 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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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.

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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 (psychological state).

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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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Demonstration (attention & perception)

• An interaction between

– attention and perception

– cognition and perception

• Tell me what you see.

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Demonstration (knowledge and perception)

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What did you see?

• What does this tell?

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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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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 lawDL/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: 10

•K:

DL/S=K

•DL: 0.25

•S: 1

•K: 0.25

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Magnitude estimation

• Assign a value to a standard stimulus

• The subject estimate the value of a target stimulus.

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Magnitude estimationStandard: == 10

Target: == ?

Standard: == 100

Target: == ?

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Standard: == 100

Target: == ?

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Standard: == 100

Target: == ?

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Steven’s power law

• 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

nKSP

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Magnitude estimation

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Steven’s power law nKSP

• 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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Standard = 100 Target = ?

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Target Your estimations0 0

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Estimating the length of stimuli

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Physical magnitudes

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P: your estimation

S: stimulus intensity

n: some value =0.33

K: some value (constant) = 21.5

nKSP

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Experiment (you are estimating the intensity of electric shock)

Standard = 100

Target = ?

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Estimating the intensity of electric shock

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Physcial magnitude

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P: your estimation

S: stimulus intensity

n: some value =1.5

K: some value (constant) = 0.1

nKSP

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Physical magnitudes

You

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Estimating electric shock

Estimating the length of lines

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Steven’s power law nKSP • 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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Threshold

• Absolute threshold

• Difference threshold

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Difference threshold

• Weber’s law

• Stevens’s law