sensation and perception chapter 3

8/8/2019 Sensation and Perception Chapter 3

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Sensation andSensation and

Perception Chapter 3Perception Chapter 3


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Basic DefinitionsBasic Definitions

SensationSensation is the process in which theis the process in which the

sense organs receptor cells aresense organs receptor cells are

stimulated and relay information tostimulated and relay information tohigher brain centershigher brain centers

PerceptionPerception is the process by which anis the process by which an

organism selects and interpretsorganism selects and interprets

sensory input so it can acquiresensory input so it can acquire

meaningmeaning


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Basic DefinitionsBasic Definitions

Perceptual systems are sets ofPerceptual systems are sets of

structures, functions andstructures, functions and

operations by which peopleoperations by which people

perceive the worldperceive the world


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Sensation and PerceptionSensation and Perception

ModalitiesModalities

DimensionsDimensions

Example: Vision

Form Color Motion Depth/Space


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PsychophysicsPsychophysics

TheThe absolute thresholdabsolute threshold is theis the

minimum level of stimulationminimum level of stimulation

necessary to excite a sensorynecessary to excite a sensorysystemsystem


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Sensory ThresholdsSensory Thresholds

TheThe difference thresholddifference thresholdis theis the

amount of change necessary toamount of change necessary to

report 50% of the time thatreport 50% of the time thatthe value of a stimulus hasthe value of a stimulus has

changedchanged


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There are two methods of studyingThere are two methods of studying

sensory thresholdssensory thresholds

1.1. Method of limitsMethod of limits2.2. Method of constant stimuliMethod of constant stimuli


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Signal detection theorySignal detection theory holds thatholds that

an observers perceptions dependan observers perceptions depend

on:on:

The intensity of a stimulusThe intensity of a stimulus

The observers motivation,The observers motivation,

criterion set by the observer, andcriterion set by the observer, and

background noisebackground noise


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The Visual SystemThe Visual System

Humans derive more informationHumans derive more information

through sight than any other sensethrough sight than any other sense

LightLight that is visible to the human eyethat is visible to the human eyeis a small part of the electromagneticis a small part of the electromagnetic

spectrumspectrum


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Figure 3.3 The Electromagnetic SpectrumFigure 3.3 The Electromagnetic Spectrum


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Figure 3.4 The Main Structures of the EyeFigure 3.4 The Main Structures of the Eye


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Structure of the EyeStructure of the Eye

TheThe corneacornea is a small, transparentis a small, transparent

bulge covering both thebulge covering both thepupilpupiland theand the

irisiris Behind the pupil is theBehind the pupil is the lenslens

Together, the cornea, the pupil, theTogether, the cornea, the pupil, the

iris, and the lens focus images ontoiris, and the lens focus images ontothe retinathe retina


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TheThe RetinaRetina

TheThe retinaretina consists of ten layers ofconsists of ten layers of

cells including:cells including:

PhotoreceptorsPhotoreceptors (light(light--sensitive cells)sensitive cells) Bipolar cellsBipolar cells

Ganglion cellsGanglion cells


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retinaretina


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The RetinaThe Retina

Two types of photoreceptors areTwo types of photoreceptors are

rodsrods andand conescones

When photopigments breakWhen photopigments break--down,down,electrochemical changes occur inelectrochemical changes occur in

the photoreceptorsthe photoreceptors


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The process by which stimuli areThe process by which stimuli are

analyzed and converted intoanalyzed and converted into

electrical impulses is calledelectrical impulses is calledtransductiontransduction

In Rods transductionIn Rods transduction

involves the breakdown ofinvolves the breakdown ofRhodopsin into Opsin andRhodopsin into Opsin and

Retinol by light hiting the rodRetinol by light hiting the rod

receptor [vitamin A]receptor [vitamin A]


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Through a process calledThrough a process called

convergenceconvergence, signals from many, signals from many

photoreceptors come together in aphotoreceptors come together in asingle bipolar cellsingle bipolar cell


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From bipolar cells, the energy isFrom bipolar cells, the energy is

transferred totransferred to ganglion cellsganglion cells

The axons of the ganglion cellsThe axons of the ganglion cellsmake up themake up the optic nerveoptic nerve whichwhich

carries information to the braincarries information to the brain

The first synapse of the ganglionThe first synapse of the ganglioncells in the brain is in thecells in the brain is in the

thalamus lateral geniculatethalamus lateral geniculate

nucleusnucleus


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The Visual CortexThe Visual Cortex

The axons of the ganglion cellsThe axons of the ganglion cells

make up themake up the optic nervesoptic nerves whichwhich

carries information to the braincarries information to the brain In the brain, information isIn the brain, information is

processed by the visual cortexprocessed by the visual cortex


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Duplicity TheoryDuplicity Theory

Duplicity theoryDuplicity theoryasserts there areasserts there are

two receptor systems in the retina,two receptor systems in the retina,

the rods and conesthe rods and cones


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Rods and ConesRods and Cones

Cones are used for day vision,Cones are used for day vision,colour vision, and finecolour vision, and fine

discriminationdiscrimination Rods are found in the rest of theRods are found in the rest of the

fovea and are used primarily forfovea and are used primarily for

night visionnight vision Eat your carrotsEat your carrots


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Rods and ConesRods and Cones

Dark adaptationDark adaptation is the increase inis the increase in

sensitivity to light when illuminationsensitivity to light when illumination

decreasesdecreases


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Higher PathwaysHigher Pathways

Each eye is connected to bothEach eye is connected to both

sides of the brainsides of the brain

Half an eyes optic nerve fibres goHalf an eyes optic nerve fibres goto the left side, and half to theto the left side, and half to the

rightright

The point of the crossover is theThe point of the crossover is theoptic chiasmoptic chiasm


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Figure 3.8 A Visual Image Is Projected to BothFigure 3.8 A Visual Image Is Projected to Both

Hemispheres of the BrainHemispheres of the Brain


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Electrochemical Basis ofElectrochemical Basis of

PerceptionPerception

Receptive fieldsReceptive fields are areas of theare areas of the

retina that, when stimulated,retina that, when stimulated,

produce a change in the firing ofproduce a change in the firing ofcells in the visual systemcells in the visual system


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Electrochemical Basis ofElectrochemical Basis of

PerceptionPerception

Hubel and Wiesel describe threeHubel and Wiesel describe three

types oftypes offeature detectorsfeature detectors

The first type is simple cellsThe first type is simple cells

The second type is complex cellsThe second type is complex cells

The third type is hypercomplex cellsThe third type is hypercomplex cells


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Eye MovementsEye Movements

SaccadesSaccades are rapid, voluntary eyeare rapid, voluntary eye

movements and the most commonmovements and the most common

type of eye movementstype of eye movements The delay of 200 to 250 msecsThe delay of 200 to 250 msecs

between saccades is abetween saccades is a fixationfixation


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Colour VisionColour Vision

When people speak of the color ofWhen people speak of the color of

an object, they are referring toan object, they are referring to

huehue Hue is a psychological term,Hue is a psychological term,

because objects themselves do notbecause objects themselves do not

possess colourpossess colour ColourColouris determined by how theis determined by how the

eyes and brain interpret reflectedeyes and brain interpret reflected

wavelengths of lightwavelengths of light


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One psychological dimension ofOne psychological dimension of

colour is huecolour is hue

A different hue is associated withA different hue is associated with

each wavelengtheach wavelength


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A second psychological dimensionA second psychological dimension

isis brightnessbrightness or how light or darkor how light or dark

the hue of an object appearsthe hue of an object appears The third psychological dimensionThe third psychological dimension

of colour isof colour is saturationsaturation ororpuritypurity


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Theories of Colour PerceptionTheories of Colour Perception

TheThe trichromatic theorytrichromatic theory developed bydeveloped by

Young and HelmholtzYoung and Helmholtz

TheThe opponent process theoryopponent process theorydeveloped by Herringdeveloped by Herring


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Trichromatic TheoryTrichromatic Theory

Trichromatic theory saysTrichromatic theory saysmixing three basic colours canmixing three basic colours can

make all coloursmake all colours

Three types of cones areThree types of cones areespecially sensitive to red,especially sensitive to red,

green, and bluegreen, and blue

If the neural output from oneIf the neural output from onetype of cone is greater than thetype of cone is greater than the

others, that receptor has aothers, that receptor has a

stronger influence on the colourstronger influence on the colour


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Opponent Process TheoryOpponent Process Theory

Opponent process theory assumesOpponent process theory assumes

there are six colours and threethere are six colours and three

types of receptors: redtypes of receptors: red--green,green,blueblue--yellow, blackyellow, black--whitewhite

Each receptor fires in response toEach receptor fires in response to

all wavelengthsall wavelengths In each pair, one receptor firesIn each pair, one receptor fires

more strongly than the othermore strongly than the other


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ColourBlindnessColourBlindness

TrichromatsTrichromats are people who canare people who can

perceive all three primary coloursperceive all three primary colours

and can see any hueand can see any hue

MonochromatsMonochromats are totally colourare totally colour

blind (less than 1% of theblind (less than 1% of the

population)population)

DichromatsDichromats have difficultyhave difficulty

distinguishing either red and greendistinguishing either red and green

oror blue and yellowblue and yellow


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Visual PerceptionVisual Perception

Size constancySize constancy is the ability of theis the ability of thevisual perceptual system tovisual perceptual system to

recognize an object remainsrecognize an object remains

constant in size determined by:constant in size determined by: Previous experience with the truePrevious experience with the true

size of the objectsize of the object

Distance between the object andDistance between the object andthe personthe person

The presence of surroundingThe presence of surrounding

objectsobjects


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Visual PerceptionVisual Perception

Shape constancyShape constancy is the ability ofis the ability of

the visual system to recognize athe visual system to recognize a

shape despite changes in itsshape despite changes in itsorientation or the angle fromorientation or the angle from

which it is viewedwhich it is viewed


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Depth PerceptionDepth Perception

Depth perception allows a person toDepth perception allows a person to

estimate distance from an object,estimate distance from an object,

and the distance between objectsand the distance between objects


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Monocular cuesMonocular cues do not dependdo not depend

on the use of both eyeson the use of both eyes

Motion parallaxMotion parallaxoccurs when aoccurs when a

moving observer stares at amoving observer stares at a

fixed pointfixed point

Objects behind the point appearObjects behind the point appear

to move in the same direction asto move in the same direction asthe observerthe observer


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A second monocular depth cue isA second monocular depth cue is

thethe kinetic depth effectkinetic depth effect

In the kinetic depth effect, objectsIn the kinetic depth effect, objectswhich look flat when stationarywhich look flat when stationary

appear to be three dimensionalappear to be three dimensional

when set in motionwhen set in motion


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Other monocular cues arise fromOther monocular cues arise from

the stimulus itselfthe stimulus itself

InIn linear perspectivelinear perspective, l, larger orarger ortaller objects are perceived astaller objects are perceived as

closercloser

Linear perspective makes distantLinear perspective makes distantobjects appear closer togetherobjects appear closer together


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InterpositionInterposition is when one objectis when one object

blocks out another, it seemsblocks out another, it seems

closercloser TextureTexture is surfaces that haveis surfaces that have

little texture or detail seem morelittle texture or detail seem more

distantdistant


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InIn highlighting and shadowing,highlighting and shadowing,

light objects appear near, darklight objects appear near, dark

objects seem distantobjects seem distant Atmospheric perspectiveAtmospheric perspective relatesrelates

to wavelengths of light, withto wavelengths of light, with

distant objects appearing moredistant objects appearing more

blueblue


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AccommodationAccommodation is changes in theis changes in the

shape of the lens of the eye asshape of the lens of the eye as

distance to an object changesdistance to an object changes


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SoundSound

SoundSound is the psychologicalis the psychologicalexperience that occurs when changesexperience that occurs when changesin air pressure affect the receptivein air pressure affect the receptiveorgan for hearingorgan for hearing

FrequencyFrequency is the number of completeis the number of completechanges in air pressure that occurschanges in air pressure that occurs

during a given unit of timeduring a given unit of time


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SoundSound

PitchPitch is the psychologicalis the psychologicalexperience that correspondsexperience that corresponds

with the frequency of anwith the frequency of anauditory stimulusauditory stimulus


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SoundSound

AmplitudeAmplitude ((intensity)intensity) is the totalis the total

energy of a sound waveenergy of a sound wave

Amplitude determines the loudnessAmplitude determines the loudnessof soundof sound


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SoundSound

TimbreTimbre is the quality of a soundis the quality of a sound

(the specific mixture of amplitudes(the specific mixture of amplitudes

and frequencies that makeand frequencies that make--up aup asound)sound)


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Structure of the EarStructure of the Ear

The receptive organ forThe receptive organ for auditionaudition

is the earis the ear

The ear translates physicalThe ear translates physicalstimuli (sound waves) intostimuli (sound waves) into

electrical impulses the brain canelectrical impulses the brain can

interpretinterpret The ear has three major parts:The ear has three major parts:

the outer ear, middle ear, andthe outer ear, middle ear, and

inner earinner ear


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Figure 3.24 The Major Structures of the Ear


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The eardrum (The eardrum (tympanictympanic

membrane)membrane) is the boundaryis the boundary

between the outer and middlebetween the outer and middleearear

The eardrum responds toThe eardrum responds to

sound waves by vibratingsound waves by vibrating

Large forces striking theLarge forces striking the

eardrum are converted toeardrum are converted to

smaller forces by the bonessmaller forces by the bones


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The three bones of the middle earThe three bones of the middle ear

stimulate thestimulate the basilar membranebasilar membrane,,

which runs down the middle of thewhich runs down the middle of thecochleacochlea

Sound waves of differentSound waves of different

frequencies stimulate differentfrequencies stimulate differentareas of the basilar membraneareas of the basilar membrane


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The cells are responsible for theThe cells are responsible for the

transduction of mechanical energytransduction of mechanical energy

into neural impulsesinto neural impulses Neural impulses travel via theNeural impulses travel via the

auditory nerve to the midbrain,auditory nerve to the midbrain,

then to the auditory cortexthen to the auditory cortex


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Theories ofHearingTheories ofHearing

Place theoriesPlace theories claim the analysisclaim the analysis

of sound occurs in the basilarof sound occurs in the basilar

membranemembrane Different frequencies andDifferent frequencies and

intensities effect different partsintensities effect different parts

(places) of the membrane(places) of the membrane


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Sound LocalizationSound Localization

Sound localization involvesSound localization involves

detecting where a sound comesdetecting where a sound comes

fromfrom

Sounds produced to the left of theSounds produced to the left of the

head arrive at the left ear beforehead arrive at the left ear before

the right sidethe right side


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Hearing ImpairmentsHearing Impairments

Conduction deafnessConduction deafness results fromresults from

interference with the transmissioninterference with the transmission

of sound to the neural mechanismof sound to the neural mechanism

of the inner earof the inner ear

Sensorineural deafnessSensorineural deafness resultsresults

from damage to the cochlea, thefrom damage to the cochlea, the

auditory nerve, or higher auditoryauditory nerve, or higher auditory

processing centresprocessing centres


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TasteTaste

Taste is a chemical sense inTaste is a chemical sense inwhich food partially dissolved inwhich food partially dissolved in

saliva stimulatessaliva stimulates taste budstaste buds

All taste cells are sensitive to allAll taste cells are sensitive to alltaste stimuli, but some are moretaste stimuli, but some are more

sensitive to specific taste stimulisensitive to specific taste stimuli

There are four basic taste stimuli:There are four basic taste stimuli:sweet, sour, salty, bittersweet, sour, salty, bitter


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TasteTaste

Taste sensitivity seems to beTaste sensitivity seems to be

genetically determinedgenetically determined

Taste also depends on the numberTaste also depends on the numberof taste buds a person hasof taste buds a person has

Past experience is also importantPast experience is also important

in the taste of foodsin the taste of foods


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SmellSmell

Like taste,Like taste, olfactionolfaction (the sense of(the sense of

smell) is a chemical sensesmell) is a chemical sense

The receptors for smell are theThe receptors for smell are theolfactory receptor cellsolfactory receptor cells contained incontained in

thethe olfactory epitheliumolfactory epithelium


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SmellSmell

The olfactory bulbs areThe olfactory bulbs are

enlargements of the olfactoryenlargements of the olfactory

nervenerve

The olfactory nerve transmitsThe olfactory nerve transmits

information to the braininformation to the brain


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Smell and CommunicationSmell and Communication

Pheromones may influence thePheromones may influence the

physiology of another animalphysiology of another animal

They are widely recognized asThey are widely recognized asinitiators of sexual activity amonginitiators of sexual activity among

animalsanimals


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TouchTouch

The skins consists of three layers:The skins consists of three layers:

The epidermis, the top layer,The epidermis, the top layer,

consists primarily of dead cellsconsists primarily of dead cells The second layer, the dermis,The second layer, the dermis,

contains living cellscontains living cells

The inner layer, the hypodermis,The inner layer, the hypodermis,is a thick, insulating cushionis a thick, insulating cushion


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PainPain

Pain is due to the operation ofPain is due to the operation offreefree

nerve endings,nerve endings, microscopic ends ofmicroscopic ends of

afferent neurons not connected toafferent neurons not connected to

any specific organany specific organ

The perception of pain is bothThe perception of pain is both

physical and psychologicalphysical and psychological


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PainPain

Neuromatrix theoryNeuromatrix theorycontends thecontends the

brain possesses a neural network,brain possesses a neural network,

the bodythe body--self neuromatrix (BSN)self neuromatrix (BSN)

The BSN integrates inputs toThe BSN integrates inputs to

produce an output pattern weproduce an output pattern we

experience as painexperience as pain


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PainPain

A second influence is visual andA second influence is visual and

other sensory inputs thatother sensory inputs that

influence the interpretation ofinfluence the interpretation ofthe situationthe situation

A third influence is activity ofA third influence is activity of

the bodys stress regulationthe bodys stress regulation

systemsystem


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EndorphinsEndorphins

EndorphinsEndorphins are painkillers that areare painkillers that are

produced naturally in the brain andproduced naturally in the brain and

pituitary glandpituitary gland

Endorphins bind themselves toEndorphins bind themselves to

receptor sites in the brain andreceptor sites in the brain and

spinal cordspinal cord

Endorphins prevent pain signalsEndorphins prevent pain signals

from passing to higher levels offrom passing to higher levels of

the nervous systemthe nervous system


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AcupunctureAcupuncture

In acupuncture, long, slenderIn acupuncture, long, slender

needles are inserted into theneedles are inserted into the

body at specific locationsbody at specific locations

Acupuncture may stimulate aAcupuncture may stimulate a

release of endorphinsrelease of endorphins

It may be effective withIt may be effective withmigraines, arthritis, andmigraines, arthritis, and

postoperative pain from dentalpostoperative pain from dental

surgerysurgery


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Pain ManagementPain Management

For people with chronic pain, drugFor people with chronic pain, drug

treatment may be ineffective or eventreatment may be ineffective or even

dangerous because high doses maydangerous because high doses may

be neededbe needed


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KinesthesisKinesthesis

KinesthesisKinesthesis is the awareness ofis the awareness of

movements of the muscles, tendons,movements of the muscles, tendons,

and jointsand joints

Kinesthesis is based onKinesthesis is based on

proprioceptive cuesproprioceptive cues oror ssensory cuesensory cues

that come from within the bodythat come from within the body


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The Vestibular SenseThe Vestibular Sense

TheThe vestibular sensevestibular sense is the senseis the sense

of bodily orientation and posturalof bodily orientation and postural

adjustmentadjustment

It helps maintain balance andIt helps maintain balance and

sense of equilibrium, andsense of equilibrium, and

provides information aboutprovides information about

orientations of head and bodyorientations of head and body

Essential structures are in theEssential structures are in the

earear


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Extrasensory PerceptionExtrasensory Perception

ESP includes four phenomenon:ESP includes four phenomenon:

TelepathyTelepathy(transfer of thoughts(transfer of thoughts

from one person to another)from one person to another) ClairvoyanceClairvoyance (recognizing objects(recognizing objects

or events not discernable byor events not discernable by

normal sensory receptors)normal sensory receptors)


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Extrasensory PerceptionExtrasensory Perception

PrecognitionPrecognition (inexplicable(inexplicable

knowledge of future events)knowledge of future events)

PsychokinesisPsychokinesis (ability to move(ability to moveobjects with mental powersobjects with mental powers

sensation and perception chapter 3

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