how do we study sensation? psychophysics: the study of the relationship between physical stimuli and...

How Do We Study Sensation?How Do We Study Sensation?Psychophysics:

The study of the relationship between physical stimuli and the perception of them. Psychophysics also studies the physical characteristics of stimuli such as amp and loudness of sound.

Psychophysics:The study of the relationship between physical stimuli and the perception of them. Psychophysics also studies the physical characteristics of stimuli such as amp and loudness of sound.

Gustav FechnerGustav FechnerFather of Psychophysics

(and a lot of fun at parties)

Gustav FechnerGustav FechnerFather of Psychophysics

(and a lot of fun at parties)

Prepared by Dr. Gordon Vessels 2004

Sensation & Perception • Sensation - the process of transducing physical energy from the environment into electrical energy in neurons.

• Sensory Receptors• Transduction

• Perception – the selection, organization, & interpretation of input from sensory organs that takes place in the cerebral cortex. Prepared by Dr. Gordon Vessels 2004

Violet360nmIndigoBlueGreen500nm

YellowYellowOrangeOrange600nm600nmRed700nm

Violet360nmIndigoBlueGreen500nm

YellowYellowOrangeOrange600nm600nmRed700nm

Electromagnetic Spectrum

Electromagnetic Spectrum

Transduction - the process

of convertingstimulus energy to neural energy


CORNEA

LENS

IRIS

SCLERA

CHOROID

RETINA

CILIARY MUSCLE

OPTIC NERVE

Picture modeled after one used by Hiohde at http://phys2.med.osaka-u.ac.jp/~hiohde/gannka/eyeball.html [email protected]

Macula

Optic Nerve

Ciliary Muscle (controls the Lens) Retina(Rods

and Cones

Eye Muscle

IrisSclera (white of the eye)

Lens

Cornea

Pupil

Fovea (point of central

focus

Blind Spot

Eye Muscle

Arranged Dr. Gordon Vessels 2004

LongerWavelengt

hLower

FrequencyShorter

Wavelength

HigherFrequency

Properties of

Created by Dr. Gordon Vessels 2004

Properties of

Light

Properties of

Light

SmallerAmplitude

DullColors

SmallerAmplitude

DullColors

HigherAmplitude

BrightColors

HigherAmplitude

BrightColors


Visible spectrum: 380-760 nm (nm is a billionth of a meter)

The Electromagnetic Spectrum

The Visible Spectrum

Radar Television & Radio Bands

AC Circuits

Infrared Rays

Ultraviolet Rays

X - RaysGamma Rays

Wavelength in Nanometers


Retina (Rods & Cones)

Cones Rods Number 6 million 125 million Location in Retina Center Periphery Sensitivity to Light Low High Color Sensitive Yes No

RetinaRetinaRetinaRetina


Photoreceptors

Rods• Light-sensitive• High sensitivity

– Perform in poor light

• Low acuity• High concentration

in periphery of retina

Cones• Color-sensitive• Low sensitivity

– Need bright light• High acuity• High concentration

at the fovea

Rods & cones connect to ganglion cells the axons of which comprise the optic

nervePrepared by Dr. Gordon Vessels 2004

Cross section of the central retina

Ganglion cells

Ganglion cells

Bipolar cells

Photo Recepto

r cells

Retin

aBipolar

cells Fovea

Pigmented Epithelium

Rods Cones

Arranged by Dr. Gordon Vessels 2004

Direction of Light Rays

Cells in the RetinaCells in the Retina

LightLight

Ganglion CellsGanglion Cells

InterneuronsInterneurons

Bipolar CellsBipolar Cells


ConeCone RodRod

Lateral Geniculate Nucleus

Superior Culliculus in

MidbrainOptic Radiation

Pulvinar Nucleus

Temporal

Tempora

Visual Cortex

Nasal

Optic Chiasm

Right Visual FieldLeft Visual

Field

○

Optic Nerve

Optic Nerve

Localization of objects: from Optic Nerve to Superior Culliculus

Localization of objects: from Optic Nerve to Superior Culliculus

Superior Culliculus in

Midbrain

Primary Visual Cortex

Superior Culliculus

Lateral Geniculate Nucleus

Optic Chiasm

Optic Nerve

General perception: from Optic Nerve to Optic Chiasm

General perception: from Optic Nerve to Optic Chiasm


Visual Information Processing

Retinal ProcessingRods & Cones Bipolar Cells Ganglion Cells

Feature DetectionDetector cells respond to elementary features

AbstractionHigh-level cells respond to combined information from feature-detector cells

RecognitionBrain matches the constructed

image with images stored in long-term memoryClick here to learn more


http://faculty.washington.edu/chudler/eyecol.html

http://www.mbfys.kun.nl/mbfys/education/medical/webteach/yin/newcourse524/visual_system_beter/vision.htm

Recap: How the Eye Works

• Light reflects off objects. Reflected light passes through pupil and lens to focus on the retina.

• Muscles change the shape of the lens to focus the image on the retina.

• Receptors in the retina (both rods & cones) change light into neural signals (transduction).

• Cones provide for visual acuity.• Rods offer night vision + brightness

information.• Daytime vision is best at the fovea where

cones are predominant.


Dark & Light AdaptationDark & Light Adaptation

Adaptation happens when the eye grows more or less sensitive to light

Modeled after a PPT slide created by Dr. Kevin Richardson in 1998 and available through the American Psychological Society.

Time in Dark in Minutes

Lo

g T

hre

sho

ld in

M

icro

lam

ber

ts

8

7

6

5

4

35 10 15 20 25 30

Absolute ThresholdsAbsolute Thresholds

Vision:On a clear, dark night

you can see a candle from

30 miles away.

What is the minimum stimulation necessary to detect a stimulus 50% of the time?


Detecting a weak signal from a stimulus depends on

Detecting a weak signal from a stimulus depends on1. The signal’s

strength and2. Your internal

mental state (experience, motivation, mood, fatigue, needs, adaptation, etc.

1. The signal’s strength and

2. Your internal mental state (experience, motivation, mood, fatigue, needs, adaptation, etc.

Do absolute

thresholds really exist?

Do absolute

thresholds really exist?


What is the minimum difference between two stimuli that a

person can detect 50% of the time?

What is the minimum difference between two stimuli that a

person can detect 50% of the time?

Difference Thresholds

(JND)

Difference Thresholds

(JND) (Ernst) Weber’s Law“Regardless of

magnitude, two stimuli must differ by a

constant proportion for the difference to be

noticeable.”


Color VisionDo objects possess color?Do objects possess color?

Is a lemonIs a lemon

NO!!NO!! Light has no color.Light has no color.

Is a chili pepper rrrrrrrrIs a chili pepper rrrrrrrr

RED?RED?

YELLOWYELLOW

??

I said No !!!!I said No !!!!Modeled after a PPT slide created by Dr. Kevin Richardson in 1998 and made available through the American Psychological Society

Trichromatic Theory of Color Vision

Helmholtz 1852

Three types of coneThree types of conereceptors are sensitive to receptors are sensitive to

different wavelengths of lightdifferent wavelengths of light.

Short Medium Long

People see colors because their People see colors because their eyes do mixing by adjusting eyes do mixing by adjusting

the ratio of stimulus input the ratio of stimulus input from these three types of cones.from these three types of cones.

Modeled after a PPT slide created by Kevin Richardson in 1998 and made available through the American Psychological Society

Opponent Process Theory

R

G

B

Y

B

W

Eye contains 3 Eye contains 3 mechanisms mechanisms that produce that produce antagonistic antagonistic responses to responses to

three pairs three pairs of colors.of colors.

Why?Why?Afterimages Afterimages

and color and color deficiencydeficiency

Click here for more

Click here for more

Click here for more


http://www.psych.ucalgary.ca/PACE/VA-Lab/colourperceptionweb/theories.htm

http://www.yorku.ca/eye/model.htm

http://www.yorku.ca/eye/opponent.htm

An illusion invented by the German psychologist Wilhelm Wundt in the 19th century. In this figure, the two red horizontal lines are both straight, but they look as if they are bowed inwards. The distortion is induced by the crooked lines on the background. Arranged by Gordon Vessels, 2005

SizeSize HeightHeight Linear Perspective

Linear Perspective

InterpositionInterposition Texture Gradient

Texture Gradient

ShadingShading Atmospheric Perspective

Atmospheric Perspective

Pictorial Cues

Pictorial Cues

Eye Muscles

Eye Muscles

No MovementNo Movement MovementMovement

Motion ParallaxMotion Parallax Kinetic Depth EffectKinetic Depth Effect

AccommodationAccommodation

ConvergenceConvergence Retinal DisparityRetinal Disparity

Monocular Cues

Monocular Cues

Binocular Cues

Binocular Cues

Source of StimulationSource of Stimulation

Twelve Types of Information That Help You Determine the Distance of an Object


Photographs combined by Dr. Gordon Vessels 2004

3 Properties of Sound

Sound also travels in waves• 1. Pitch: is determined by wave

“frequency,” the number of cycles per second of a sound wave.

• 2. Loudness: is determined by wave“amplitude” or the height of thesound waves.

• 3. Timbre: is determined by the “complexity and shape” of the sound waves, and it gives sound

its unique quality.Arranged by Dr. Gordon Vessels 2004

Units of Measurement for Sound

• hertz (Hz): used to measure pitch (frequency), the number of cycles per second of the sound waves

– a baby’s cry is at about 3,000 Hz

• decibel (db): reflects the loudness (amplitude) of the sound wave

– Speech is at about 70 db


● Revolver firing at close range● PAIN THRESHOLD● Sonic Boom● Air Raid Siren● Jackhammer 3 Feet Away● Jet Plane 500 Feet Away● Stereo at Full Volume● Live Rock Music● Subway Train 20 Feet Away● Jackhammer 20 Feet Away● Heavy Truck25 Feet Away● Lawnmower, Food Blender● POTENTIAL EAR DAMAGE● Dog Barking 10 Feet Away● Infant Crying Ten Feet Away● Heavy Traffic, Vacuum Cleaner● Doorbell 10 Feet Away● Normal Conversation● Window Air Conditioner● Car Engine Idling● Heavy Rain on Window● Person walking on Hard Floor● Knock at the Door● Car on Highway Windows Up● Light Rain on Window● Person Talking in Closed Room● Food Frying● Leaves Rustling in Wind● Whisper● Clock Ticking● Person Breathing

Deci

bels

of

Sou

nd

130

120

110

100

90

80

70

60

50

40

30

20

10


Sound WavesSound Waves

Amplitude (Loudness)Strength or height

of the wave

Frequency (Pitch)Distance between consecutive peaks

Mix (Timbre)Interaction of different

waves

1 Hertz = 1 Cycle/Sec1 Hertz = 1 Cycle/Sec Human HearingHuman Hearing20 - 20k Hz20 - 20k Hz

Arranged by Dr. Gordon Vessels 2004; modeled after a slide creared by Dr. Kevin Richardson (1998) and available through the American Psychological Society.

malleus

cochlea

incus

pinnapinna

tympanic membranetympanic membrane

auditory/8th nerve

Outer EarOuter Ear

Tympanic MembraneTympanic Membrane collects sound and vibrates the ossicles

PinnaPinna collects and directs sound into auditory canalAuditory CanalAuditory Canal amplifies and funnels sound to tympanic membrane

auditory auditory canalcanal


Middle EarMiddle Ear

MalleusMalleus – vibrates and moves the Incus

IncusIncus – vibrates and moves the Stapes

StapesStapes - vibrates against Oval Window of Cochlea

MalleusMalleus – vibrates and moves the Incus

IncusIncus – vibrates and moves the Stapes

StapesStapes - vibrates against Oval Window of Cochlea

malleusmalleusmalleusmalleus incusincusincusincus

handleof malleus

handleof malleus

long processof incus

long processof incus

stapesstapesstapesstapes


Inner Ear

lateralsemicircular

canal

lateralsemicircular

canal

posteriorsemicircular

canal

posteriorsemicircular

canal

vestibulevestibule

anteriorsemicircular

canal

anteriorsemicircular

canal

cochleacochleacochleacochlea

CochleaCochlea is filled with fluid & contains Hair-cell receptors for hearing

Basilar MembraneBasilar Membrane divides length of cochlea and holds the hair cells


3. The moving fluid sets the Basilar Membrane moving inside the Cochlea

3. The moving fluid sets the Basilar Membrane moving inside the Cochlea

2. The vibrating eardrum causes the bones of the middle ear to strike each other, amplifying and carrying the vibrations to the oval window and on the fluid in the coiled Cochlea of the Inner Ear.

2. The vibrating eardrum causes the bones of the middle ear to strike each other, amplifying and carrying the vibrations to the oval window and on the fluid in the coiled Cochlea of the Inner Ear.

1. The first stage of the hearing process is a series of vibrations. Sound waves enter the Outer Ear and travel to the Eardrum, causing it to vibrate.

1. The first stage of the hearing process is a series of vibrations. Sound waves enter the Outer Ear and travel to the Eardrum, causing it to vibrate.

5. The Auditory Nerve carries impulses to the brain.

5. The Auditory Nerve carries impulses to the brain.

6. When the nerve impulses reach the Temporal Lobe, they are interpreted as sounds.

6. When the nerve impulses reach the Temporal Lobe, they are interpreted as sounds.

Cross-section of Cochlea

Cochlear Nerve Basilar MembraneCochlear Nerve

Fibers

Organ of

Corti

Tectorial Membrane Hair Cells

Eardrum

Auditory Nerve

Vestibular OrganPinna

Ear Canal

Cochlea

Extracted from Davis & Palladino text entitled Psychology; re-arranged for PPT by Dr. Gordon Vessels

2004 ©

4. The Organ of Corti on top of the Basilar Membrane also moves. Inside the Organ of Corti, thousands of tiny receptor cells are topped by a bundle of hair-like fibers. As the Basilar Membrane vibrates, the fibers bend, stimulating the Receptor Cells to send a signal through afferent nerve endings, which join to form the Auditory Nerve

4. The Organ of Corti on top of the Basilar Membrane also moves. Inside the Organ of Corti, thousands of tiny receptor cells are topped by a bundle of hair-like fibers. As the Basilar Membrane vibrates, the fibers bend, stimulating the Receptor Cells to send a signal through afferent nerve endings, which join to form the Auditory Nerve

Hair Cell in the Organ of Corti

Supporting Cells

Hair Cells

Efferent Nerve Ending

Afferent Nerve Ending

Cell Nuleus

Hair Fibers

Basilar Membrane


Stages in Audition• External Ear (Pinnae)

• Middle Ear

• Inner Ear (Cochlea)

• Inner Hair Cells

• Type I Spiral Ganglion Cells

• Cochlear Nucleus (dorsal CN and ventral CN)

• Medial Nucleus of the Trapezoidal Body

• Lateral Superior Olivary Nucleus

• Medial Superior Olivary Nucleus

• Lateral Lemniscus

• Central Nucleus of the Inferior Colliculus

• Medial Geniculate Nucleus

• Auditory CortexSlide # 3

Source: Erwin, Harry R (n.d.). The auditory system. A PPT slide set accessed online at http://www.cet.sunderland.ac.uk/~cs0her/Auditory%20System.ppt#1

Auditory Pathway

Eustachion Tube

Vestibular Cochlear

Nerve

Semicircular Canals

Cochlea

Stapes

IncusEardrum

StapesMalleus

Pinna

Lobule

External Auditory

Canal


Diana Deutsch is a Professor of Psychology at the University of California, San Diego who conducts research on perception and sound memory, including music. She discovered many musical illusions and paradoxes: the octave illusion, the scale illusion, the glissando illusion, the tritone paradox, and the cambiata

illusion. She studies the way we hold music in memory and how we relate the sounds of speech and music. Her ongoing

research focuses on the question of absolute pitch or why some rare individuals have it. Information retrieved from Dr. Deutsch at http://www-psy.ucsd.edu/%7Eddeutsch/

The pattern that produces the cambiata illusion, and a way it is often perceived.

Underlined words above are links to webpages


Pictures are copied from Dr. Deutsch’s CDs available online at the address

above.

Exploring the Sense

of Smell

Olfactory Epithelium

Olfactory Receptor Cells

Olfactory Bulb

Nasal Chache

Bone

Olfactory Nerve

Olfactory Muccsa

A Sniff

Breathing In Normally

Breathing Out Normally

Olfactory Bulb

Olfactory Bulb

Olffactory Bulb


Receptor Cilia

Olf

acto

ry

Ep

ith

eliu

mM

ucu

s

Layer

The Sense of Smell

NEUROBIOLOGYGary G. Matthews

Blackwell Science

Modified for PPT slide by Dr. Gordon Vessels

Bone at Base of

Skull

Support Cells}

}}


Basal Cell To

Brain

Olfactory Receptor

Cell

To Brain

Membrane Depolarization

Odorant Receptor Protein

Cilium of Olfactory

Cell

Adenylyl cyclase

Ca 2+ Na+

Ca 2+Cl-

cAMP

Ca 2+ Na+

Cl-

Dendrite of Olfactory

Cell

cAMPATP

Ca2+

Membrane Depolarizatio

n


Odorant Molecules

G-Protein

Epithelial Cells


Sense of Smell

Bone

Olfactory Bulb

Nerve Axons

Cilia

Sensory Cells

Olfactory Nerve

Volatile Molecule

s

(a) Taste buds line the trenches around tiny bumps on the tongue called papillae. (b) There are three types of papillae that are distributed on the tongue. The taste buds found in each show different sensitivities to the four basic tastes (see graph at the top). This sensitivity to the primary tastes varies across the tongue, but they are small. All four can de detected wherever there are taste receptors.

(a) (b)

Fungiform Papillae

CircumvallatePapillae Foliate

Papillae

Tas

te S

tren

gth

SweetSalty

Sour Bitter

Taste Buds

Tongue

The Sense of Taste


Top-Down versus Bottom-Up Perception

Top-Down versus Bottom-Up Perception

• Top-Down– Perceive the whole and then individual

parts as needed.– Experience-driven as opposed to

stimulus or input-data driven.– Quick and highly inferential but also a

source of misperception.

• Bottom-up– Perceive the individual parts and

organize them into a whole, if possible.– Information available in the stimulus

itself.

• Top-Down– Perceive the whole and then individual

parts as needed.– Experience-driven as opposed to

stimulus or input-data driven.– Quick and highly inferential but also a

source of misperception.

• Bottom-up– Perceive the individual parts and

organize them into a whole, if possible.– Information available in the stimulus

itself.


Bottom-Up Processing

Prior Knowledge, Experience, etc.


Stimuli ProcessingStimuli Processing

PerceptionPerception

Stimuli InputCreated by Dr. Gordon Vessels 2005

David Marr’s Computational Bottom-Up Approach

• Marr wanted to understand mechanisms of vision rather than just behaviors associated with it.

• …he wanted to link neurophysiology with psychology.

• He took an information processing view of the mind…

• …and aimed to describe perception in terms of computations on sense data…

• …to extract high level visual experience.Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at

http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.

Marr’s Stages of Visual Processing

• Marr proposed there were distinct stages of processing in visual perception:

» Stage 1: Raw Primal Sketch

» Stage 2: Complete Primal Sketch

» Stage 3: 2½D Sketch

» Stage 4: Full 3D Representation

Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.

Stage 1: Raw Primal Sketch

This involves the extraction of information regarding edges and

intensity changes.Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.

Stage 2: Complete Primal Sketch• After the Raw Primal Sketch…

• Marr [proposed]… we create a Complete Primal Sketch by grouping surfaces and common areas.

• The Gestalt Psychologists of the early 19th Century demonstrated many different ways in which we can group objects.


Stage 3: 2½D Sketch

• After gaining information about groupings and surfaces, the viewer needs some spatial information.

• Marr called this stage the 2½D Sketch to emphasis that this stage does not give a full 3D representation.

• Rather, just an estimate of the spatial locations of objects and materials in relation to the viewer.


2½ D Sketch: Depth Cues2½ D Sketch: Depth Cues

• We perceive much information from which we infer depth:

» Binocular disparity

» Texture gradients

» Occlusion

» Convergence

» Relative Size

• We perceive much information from which we infer depth:

» Binocular disparity

» Texture gradients

» Occlusion

» Convergence

» Relative Size


Stage 4: 3D Representation

• The final stage of Marr’s theory.

• A full 3D description of our spatial environment involving the identification of the structure of objects and materials in our visual field.

• It allows us to work out the 3D environment from a non-egocentric point-of-view.


Gregory on Top-Down Perception • Gregory proposes that we use our prior

“experience of the world to shape how we perceive” stimuli we encounter in it.

• His theory of perception is called Top-Down,

• Which means we use activated conceptual schemas and memory networks (our stored knowledge), more or less automatically and subconsciously, to shape our perceptions or to interpret our sensory input ― sometimes correctly and sometimes not.

• He confirmed many of his theoretical propositions using visual illusion research.

Primary source Bell, Vaughan (2004). Perceptions and perceptual distortions, a PPT show accessed at http://www.cf.ac.uk/psych/home/bellv1/conf/VaughanPerceptionLecture2004.ppt#1. Written permission granted 5-5-05.

Top-Down Processing



Stimuli Input

Prior Knowledge, Experience, etc. Prior Knowledge, Experience, etc.

Personality Temperament

Culture Social Class

Values Beliefs

Prejudices Attitudes

Immediate Mental Set

Presence of Authority

Present Fatigue Energy Level

Prior Stimuli Perceived

Occupation Education

Needs, Moods Mental Health

Knowledge Vocabulary

Specific Life Experiences

Long-term Memory Schemas


If all of these people were at the same football game, who among them was most likely to have perceived what actually happened on a controversial play where the receiver may have fumbled the ball before his knees touched the ground? Whose perceptions were the most bottom up? Whose perceptions were the most top-down and thus influenced and quickened in terms of inference by their present needs, biases, and heightened emotion? Whose perception may have been the most accurate and objective based on his or her knowledge of the game? When the head referee reviewed the replays, did he use top-down or bottom-up perception primarily? What top-down influence may have made it possible for his perceptions to have been highly accurate? Did these people literally see something different? Do they really believe what they claimed to have seen?

What do you see? A face looking

down? The word Liar in script or cursive? Those who first read stories about deception were more inclined than others to see

the word Liar.

What do you see? The word liar in

script or cursive? A face looking down?

Those shown artwork with faces were

more inclined than others to see the

word liar.


Top-Down & Bottom-Up Processing





Stimuli InputCreated by Dr. Gordon Vessels 2005

how do we study sensation? psychophysics: the study of the relationship between physical stimuli and...

Documents

gordon vessels

sensation perception

optic nerveprepared

optic chiasmarranged

physical stimuli

fovearods cones

neural activity

electrical energy