Chapter 5 Perception Chapter 5 Perception and Realityand Reality

McElhaneyMcElhaney

AP OutlineAP Outline

IV. Sensation and IV. Sensation and (7–9%)(7–9%)

► Thresholds Thresholds ► Sensory Sensory

Mechanisms Mechanisms ► Sensory Adaptation Sensory Adaptation PerceptionPerception ► Attention Attention ► Perceptual Perceptual

Processes Processes

► ThresholdThreshold► Absolute ThresholdAbsolute Threshold► Difference ThresholdDifference Threshold► Physical, Psychological, and Physical, Psychological, and

physiological variables physiological variables affected by thresholdsaffected by thresholds

► Signal Detection TheoriesSignal Detection Theories► Absolute Threshold TheoryAbsolute Threshold Theory► Sensory ReceptorsSensory Receptors► Transduce of energy for Transduce of energy for

nervous systemnervous system► Anatomy, Anatomy, ► Function, Function, ► Eye and earEye and ear► Color theories of visionColor theories of vision► AuditionAudition► Perceptual acuityPerceptual acuity► Sensory adaptationSensory adaptation► Sensory disorders Sensory disorders ► Deafness Deafness ► ColorblindnessColorblindness

Sensation = Sensation = Data Reduction Data Reduction SystemSystem

► 5 senses work 5 senses work similarly:similarly:

► SelectSelect► AnalyzeAnalyze► FilterFilter

► Process identifies Process identifies meaningful meaningful information.information.

InformationInformation

All of the Senses:All of the Senses:

►Use Use Transduction:Transduction: The process of changing energy (stimulus) The process of changing energy (stimulus)

to a form that can be processed by the to a form that can be processed by the nervous system-nervous system-

For example- light to a form that can be For example- light to a form that can be recognized by the retina.recognized by the retina.

Sensory AnalysisSensory Analysis

►As senses process information (from As senses process information (from environment) environment)

►The senses divide the world into The senses divide the world into perceptual features- perceptual features- or basic stimulus or basic stimulus patternspatterns Example:Example: Vision features include: lines, shapes, Vision features include: lines, shapes,

edges, spots, colorsedges, spots, colors

Fig. 5.1 Visual pop-out. (Adapted from Ramachandran, 1992b.) Pop-out is so basic that babies as young as 3 months respond to it (Quinn & Bhatt, 1998)

Perceptual Feature

Sensory CodingSensory Coding

►After sense info is analyzedAfter sense info is analyzed► It is It is converted to neural messagesconverted to neural messages – –

able to be understood by the brain.able to be understood by the brain.

Sense Organs and Sense Organs and Sense Sense LocalizationLocalization

► EyesEyes► EarsEars► TongueTongue►NoseNose► SkinSkin

► The type of The type of sensation you sensation you experienceexperience

►Depends on Depends on which which brain area is brain area is activatedactivated VisionVision AuditoryAuditory TasteTaste TouchTouch

All of the Senses include All of the Senses include Concept of Concept of

►Absolute Absolute ThresholdThreshold:: The minimum amount of energy necessary The minimum amount of energy necessary

for sensation to occurfor sensation to occur.. This is after transduction-This is after transduction- Immediate response in the brainImmediate response in the brain Recall limits of senses:Recall limits of senses: Dog whistles- Dog whistles-

humans do not have awareness because humans do not have awareness because they are below the minimum threshold of they are below the minimum threshold of human awareness.human awareness.

40,000 hertz (hertz = vibrations per 40,000 hertz (hertz = vibrations per second)second)

Difference Thresholds and Difference Thresholds and JNDJND

►Q: How much must a stimulus change Q: How much must a stimulus change before it is noticeably different?before it is noticeably different?

► JNDJND= = Just Noticeable DifferenceJust Noticeable Difference► Just Noticeable DifferenceJust Noticeable Difference= the change in = the change in

stimulus intensity to be noticed between stimulus intensity to be noticed between being noticed and not noticed.being noticed and not noticed.

►Weber’s Law:Weber’s Law: The amount of change needed The amount of change needed to produce a constant JND is a constant to produce a constant JND is a constant proportion of the original stimulus intensity proportion of the original stimulus intensity (See page 178) 1 candle to increase need 10 (See page 178) 1 candle to increase need 10 more… (more… (Web SiteWeb Site))

► Relates to SensitivityRelates to Sensitivity ratios -hearing is much ratios -hearing is much more sensitive than taste.more sensitive than taste.

Perceptual DefensePerceptual Defense

►Thresholds vary for different people and Thresholds vary for different people and can changecan change

►The The resistance to perceiving threateningresistance to perceiving threatening or disturbing or disturbing stimulistimuli = = Perceptual Perceptual DifferenceDifference

►We resist info that causes anxiety, We resist info that causes anxiety, discomfort or embarrassmentdiscomfort or embarrassment

What is Subliminal What is Subliminal Perception?Perception?

► LimenLimen= (threshold or limit) for awareness= (threshold or limit) for awareness Below the normal threshold= Below the normal threshold= SubliminalSubliminal

► Krosnick Study- Krosnick Study- emotional images inserted emotional images inserted too fast to be recognized- too fast to be recognized-

► Caused altered impressionsCaused altered impressions

►Not really effective in advertising. Not really effective in advertising. ► Vokey and Read study for Rock Music- Vokey and Read study for Rock Music- Back Back

messaging messaging (had no known effect) (had no known effect)► Is HypnopIs Hypnopæædia- Brave New World- is this dia- Brave New World- is this

Subliminal?Subliminal?

Identify properties/function Identify properties/function of Anatomy of the Eye:of Anatomy of the Eye:

1.1. LensLens

2.2. RetinaRetina

3.3. CorneaCornea

4.4. FoveaFovea

5.5. Optic NerveOptic Nerve

6.6. IrisIris

7.7. PupilPupil

8.8. Blind SpotBlind Spot

9.9. Aqueous HumorAqueous Humor

10.10. Vitreous HumorVitreous Humor

11.11. Ciliary Muscle Ciliary Muscle

12.12. ScleraSclera

13.13. ConesCones

14.14. RodsRods

Structure of EyeStructure of Eye► Like a Like a CameraCamera► Cornea (Cornea (clear membrane-clear membrane-

bends light inward)bends light inward) to focus to focus imagesimages

► On a light sensitive layer On a light sensitive layer ► Back of Back of closed space = closed space =

layer oflayer of photo-receptors photo-receptors► In In Retina Retina (thick as postage (thick as postage

stamp)stamp)► MusclesMuscles alter shape alter shape

of lens = focusof lens = focus► AccommodationAccommodation is is

another name for another name for changing distance changing distance

► >-(>-(----)----)► >-(->-)>-(->-)

Structure of the EyeStructure of the Eye

► IrisIris controls amount controls amount of light entering eyeof light entering eye ColoredColored Muscle that expands Muscle that expands

and contractsand contracts Changes size of pupilChanges size of pupil

►DilationDilation= enlarge= enlarge► ConstrictionConstriction= =

narrownarrow

Virtuous Humor- Jelly like substance fills the eyeball

VisionVision►Depends on Wavelength= the Visible Depends on Wavelength= the Visible

spectrum (Electromagnetic energy the spectrum (Electromagnetic energy the eyes respond to)eyes respond to)

VisionVision► Wavelength = ?Wavelength = ?► Visible light startsVisible light starts @ 400 nanometers @ 400 nanometers

= one billionth of a meter= one billionth of a meter= purple or violet = purple or violet

► Long light waves=Long light waves= blue, green, yellow, blue, green, yellow, orange, and red = 700 Nanometersorange, and red = 700 Nanometers

► HueHue= basic color categories-= basic color categories- Red, orange, Red, orange, yellow, green, blue, Indigo, violet -> yellow, green, blue, Indigo, violet -> correspond to light’s wave lengthscorrespond to light’s wave lengths

► SaturationSaturation= pure color= narrow band of light= pure color= narrow band of light► Brightness-Brightness- amplitudeamplitude, height of light waves- , height of light waves-

taller taller More energy = more color, brighter more intense.More energy = more color, brighter more intense.

The RetinaThe Retina►Retina is located at the Retina is located at the back of the eyeback of the eye►Light is focusedLight is focused on to the on to the retina-retina----then ---then

sensation- is received by receptors in the sensation- is received by receptors in the retina--retina--to the to the optic nerveoptic nerve.. Photo-receptor cells= Photo-receptor cells= RodsRods and and ConesCones

Fovea- cup shape, on retina, only has cones, greatest visual Acuity- or sharpness

►Blind SpotBlind Spot- where optic nerve leave the - where optic nerve leave the eye-eye-

Rods Rods and and Cones Cones► 100 million in each eye100 million in each eye► Can not detect colorCan not detect color► Black and whiteBlack and white =pure =pure

rod visionrod vision► More More sensitive to lightsensitive to light► Allow Allow sight in dim-lightsight in dim-light► Sensitive to Sensitive to movementmovement► PeripheralPeripheral vision vision

► 6.5 million in each eye6.5 million in each eye► Work best in Work best in bright bright

lightlight► Color sensationColor sensation► Fine detailFine detail ► Mostly Mostly center of eyecenter of eye► Fovea contains only Fovea contains only

conescones► Most Most sensitive to sensitive to

yellowyellow and green color and green color

Fig. 5.8 Experiencing the blind spot. (a) With your right eye closed, stare at the upper right cross. Hold the book about 1 foot from your eye and slowly move it back and forth. You should be able to locate a position that causes the black spot to disappear. When it does, it has fallen on the blind spot. With a little practice you can learn to make people or objects you dislike disappear too! (b) Repeat the procedure described, but stare at the lower cross. When the white space falls on the blind spot, the black lines will appear to be continuous. This may help you understand why you do not usually experience a blind spot in your visual field.

Peripheral VisionPeripheral Vision

►Side vision- area outside FoveaSide vision- area outside Fovea►Rod vision- not very sharp-Rod vision- not very sharp-

LASIK- Lasor Assisted Insitu keratomileusisReshapes and stretches the corneaIncreases degree of cornea bending light

Vision ProblemsVision Problems

►HyperopiaHyperopia: Difficulty focusing nearby objects : Difficulty focusing nearby objects (farsightedness) eye is too short-(farsightedness) eye is too short-

►MyopiaMyopia: Difficulty focusing distant objects : Difficulty focusing distant objects (nearsightedness) (nearsightedness)

► AstigmatismAstigmatism: Cornea, or lens defect that : Cornea, or lens defect that causes some areas of vision to be out of causes some areas of vision to be out of focus; relatively common-lens not focus; relatively common-lens not symmetricalsymmetrical

► Lenses correct vision by changing the path Lenses correct vision by changing the path of lightof light

20/2020/20

►Visual Acuity = SharpnessVisual Acuity = Sharpness►Normal 20/20 Normal 20/20 ►20’ distance you can see what average 20’ distance you can see what average

people see at 20 ft.people see at 20 ft.►20/40 = you can only see at 20 feet 20/40 = you can only see at 20 feet

what most people see at 40 feetwhat most people see at 40 feet►20/200 = correct= legal blindness20/200 = correct= legal blindness

Color Theories- what happens in Color Theories- what happens in the eye?the eye?

►TriTrichromatic- three chromatic- three types of cones each types of cones each sensitive to sensitive to RedRed, , GreenGreen, and , and BlueBlue colorcolor

► 3 visual pigments3 visual pigments► Fire nerve impulsesFire nerve impulses

@ different rates to @ different rates to produce color produce color sensationssensations

►Opponent ProcessOpponent Process TheoryTheory Vision analyzes color Vision analyzes color

in either or in either or messagesmessages

Red or greenRed or green Yellow or blueYellow or blue Black or whiteBlack or white

After Image- “OPT”After Image- “OPT”

After ImagesAfter Images

► Visual sensations that Visual sensations that persist after stimulus is persist after stimulus is removed– “seeing removed– “seeing spots”spots”

► Relates to Relates to Opponent Opponent Process Theory-Process Theory- Fatigue caused by one Fatigue caused by one

response causes after response causes after image of image of opposite color opposite color systemsystem

► Both theories apply Both theories apply ► Tri-colorTri-color► 3 visuals Pigments= 3 visuals Pigments=

light sensitive light sensitive chemicalschemicals

► Red, Green, or BlueRed, Green, or Blue► 3 types of cones- Fire 3 types of cones- Fire

nerve impulse@ nerve impulse@ different rates to different rates to produce color produce color sensationssensations

Mechanical View of Color Mechanical View of Color SensationSensation

►Colors are influenced in the brain by Colors are influenced in the brain by other colors nearbyother colors nearby

►= Simultaneous color contrast= Simultaneous color contrast Affect perception of color (p 186)Affect perception of color (p 186)

ColorblindneColorblindnessss

►Cannot perceive colorsCannot perceive colors►Lacks cone or cones don’t functionLacks cone or cones don’t function►RareRare►Genetic- Genetic- Affecting Red and Green + Affecting Red and Green +

Blue pigments in ConesBlue pigments in Cones►Color weakness people can’t see Color weakness people can’t see

certain colorscertain colors►8% of males, 1% of women- see red-8% of males, 1% of women- see red-

green as yellow and browngreen as yellow and brown

Ishihara Test

Dark Dark AdaptationAdaptation

► IncreasedIncreased retinal sensitivity to light after retinal sensitivity to light after entering the dark; entering the dark;

►similar to going from daylight into a similar to going from daylight into a dark movie theaterdark movie theater

►RhodopsinRhodopsin: Light-sensitive pigment in : Light-sensitive pigment in the rods; involved with night visionthe rods; involved with night vision

►Night BlindnessNight Blindness: Blindness under low-: Blindness under low-light conditions; hazardous for driving at light conditions; hazardous for driving at nightnight

PixelPixel

►Dot of lightDot of light►More pixels = sharper imageMore pixels = sharper image

HearingHearing► Uses Data Reduction Uses Data Reduction ► (Select, Analyze, Filter info)(Select, Analyze, Filter info)► Stimulus for hearing = Waves Stimulus for hearing = Waves ► Vibrating objects = sound waves Vibrating objects = sound waves (rhythmic (rhythmic

movement of air molecules)movement of air molecules) Peaks = compressionPeaks = compression Valleys = rarefactionValleys = rarefaction

► FrequencyFrequency of sound waves= # waves per/sec of sound waves= # waves per/sec (Corresponds to)(Corresponds to)

PitchPitch= tone of the a = tone of the a soundsound

AmplitudeAmplitude

►Amplitude = height of sound waveAmplitude = height of sound wave Tells how much energy it containsTells how much energy it contains Relates to loudness (sound intensity)Relates to loudness (sound intensity)

Anatomy of AuditionAnatomy of Audition

PinnaPinna

Tympanic membraneTympanic membrane

Auditory OssiclesAuditory OssiclesMalleusMalleus

IncusIncus

StapesStapes

CochleaCochlea

CortiCorti

SteriocillaSteriocilla

Auditory nerve fiberAuditory nerve fiber

Sound waves are converted to nerve impulses through the Auditory Sound waves are converted to nerve impulses through the Auditory SystemSystem

Audition TheoriesAudition Theories► Frequency TheoryFrequency Theory

► As pitch increases-As pitch increases-nerve impulses of nerve impulses of same frequency are same frequency are fed to auditory nervefed to auditory nerve

► Example-> 800 Example-> 800 hertz tone= # of hertz tone= # of vibrations per vibrations per second= 800 nerve second= 800 nerve impulses per secondimpulses per second

► Place TheoryPlace Theory►Higher and lower Higher and lower

tones excite tones excite specificspecific areas of the cochleaareas of the cochlea

►Hair cells respond to Hair cells respond to area greatest area greatest movementmovement

2 Types of Deafness2 Types of Deafness

► Conduction DeafnessConduction Deafness► Transfer vibration to Transfer vibration to

inner ear is weakinner ear is weak► Ear Drum or Ossicles are Ear Drum or Ossicles are

damageddamaged

► Hearing Aid makes Hearing Aid makes sounds clearer and sounds clearer and louderlouder

► Nerve Deafness-Nerve Deafness- damage to hair cells or damage to hair cells or auditory nerveauditory nerve

► Stimulation DeafnessStimulation Deafness► Loud sounds damage Loud sounds damage

hair cells in Cochleahair cells in Cochlea► 85 decibels may cause 85 decibels may cause

permanent losspermanent loss

► Temporary Threshold Temporary Threshold shiftshift

► Partial/transitory Partial/transitory hearing loss @ 120 hearing loss @ 120 decibelsdecibels

Vestibular SystemVestibular System

► Inner EarInner Ear► Associated with motion Associated with motion

sicknesssickness► Sense organs for balance Sense organs for balance

(Fluid in the inner of the ear)(Fluid in the inner of the ear)

Fluid filled sacs- sensate movement, acceleration, & gravity

ReceptorsReceptors

Motion Sickness and Vestibular Motion Sickness and Vestibular SystemSystem

►= Sensory Conflict Theory= Sensory Conflict Theory When sensations from vestibular system When sensations from vestibular system

don’t match sensations from eyes and don’t match sensations from eyes and body = conflictbody = conflict

Causes motion sicknessCauses motion sickness

►Why?Why?►Evolution- poisons attack vestibular Evolution- poisons attack vestibular

system-system-body reacts with nauseabody reacts with nausea

OlfactionOlfaction► AgainAgain- uses - uses ► Is a chemical Is a chemical

sense sense (receptors (receptors that respond to that respond to chemical chemical molecules)molecules)

►Data Reduction & Data Reduction & Transduction- Transduction-

► Airborne Molecules Airborne Molecules contact receptor contact receptor cells in nose.cells in nose.

► 5 million nerve 5 million nerve fibers in nasal fibers in nasal passagespassages

Axons go directly to olfactory bulbs in brain

To olfactory cortex & limbic system.

AnosmiaAnosmia

►Defective senseDefective sense of smell for single of smell for single odorodor Suggests these are specific receptors for Suggests these are specific receptors for

specific odorsspecific odors 1 person in a hundred can’t smell1 person in a hundred can’t smell

Smell ReceptorsSmell Receptors►Shape of receptors impacts smellsShape of receptors impacts smells►Lock and key theory-Lock and key theory- some odors have some odors have

specific shapes that fit receptorsspecific shapes that fit receptors►# of activated receptors tells how # of activated receptors tells how

strong an odor is…strong an odor is…

►ScentScent likes and dislikes are learned likes and dislikes are learned

PheromonesPheromones

► Animals- secret- Animals- secret- Affect matingAffect mating Sexual behaviorSexual behavior Associated with Associated with

recognition of family recognition of family membermember

Territorial markingTerritorial marking► Vomeronasal organ Vomeronasal organ

(VNO) sense organ (VNO) sense organ for Pheromonesfor Pheromones

► Receptors in septumReceptors in septum

► Produces vague Produces vague feelingsfeelings

► Affects general Affects general moodmood Well beingWell being AttractionAttraction Unease and anxietyUnease and anxiety

►May cause women’s May cause women’s menstrualmenstrual cycles to cycles to synchronizesynchronize

Gustation Gustation ► Sense of TasteSense of Taste► Chemical SenseChemical Sense► Tongue includes:Tongue includes:

papillae-papillae- taste buds taste buds and receptorsand receptors

Associated with Associated with medulla oblongatamedulla oblongata

► Taste sensitivity= # Taste sensitivity= # of taste buds on of taste buds on tonguetongue

► Taste Taste preferencespreferences are acquiredare acquired

► Four basic tastes:Four basic tastes: SweetSweet BitterBitter SaltSalt SourSour

► FlavorFlavor

Somesthetic Sense Somesthetic Sense (Touch)(Touch)

► The Skin- The Skin- cutaneouscutaneous► Kinesthetic/Tactile ReceptorsKinesthetic/Tactile Receptors (movement) in (movement) in

muscles and in jointsmuscles and in joints Detect body position and movement Detect body position and movement

► Collects info- pressure, pain and Collects info- pressure, pain and temperaturetemperature

►Neurons to spinal cord-> medulla-> Neurons to spinal cord-> medulla-> thalamus->somatosensory cortexthalamus->somatosensory cortex

Where is our body most Where is our body most sensitive? Density of Receptorssensitive? Density of Receptors► Based on density of Based on density of

receptors (most to receptors (most to least)least) Lips Lips TongueTongue Face Face Hands Hands genitalsgenitals

► ReceptorsReceptors 200,000 nerve 200,000 nerve

endings for endings for temperaturetemperature

500,000 touch and 500,000 touch and pressurepressure

3 million for pain3 million for pain

Pain ReceptorsPain Receptors

►Varied distribution through the bodyVaried distribution through the body 232 pain points per square centimeter 232 pain points per square centimeter

behind the kneebehind the knee 184 in buttocks184 in buttocks 60 on the thumb60 on the thumb 44 on nose44 on nose

PainPain

Nerve Fibers Nerve Fibers Large Large SmallSmall

SkinSkin MusclesMuscles JointsJoints TendonsTendons

► Sharp bright fast Sharp bright fast ► From specific body From specific body

partsparts►Warning system Warning system

► Reminding systemReminding system► Slower nagging, Slower nagging,

aching widespreadaching widespread► Very unpleasantVery unpleasant► Reminds brain body Reminds brain body

has been injuredhas been injured

Fig.5.28 Visceral pain often seems to come from the surface of the body, even though its true origin is internal. Referred pain is believed to result from the fact that pain fibers from internal organs enter the spinal cord at the same location as sensory fibers from the skin. Apparently, the brain misinterprets the visceral pain messages as impulses from the body’s surface.

Adaptation, Attention, and Adaptation, Attention, and Sensory GatingSensory Gating

►Sensory Adaptation:Sensory Adaptation: When sensory When sensory receptors respond less to unchanging receptors respond less to unchanging stimulistimuli

►Selective Attention:Selective Attention: Voluntarily Voluntarily focusing on a specific sensory inputfocusing on a specific sensory input

►Sensory Gating:Sensory Gating: Facilitating or blocking Facilitating or blocking sensory messages in spinal cordsensory messages in spinal cord

Gate Control Theory of PainGate Control Theory of Pain

►Gate Control Theory:Gate Control Theory: Pain messages Pain messages from different nerve fibers pass from different nerve fibers pass through the same “neural” gate in the through the same “neural” gate in the spinal cord.spinal cord. If gate is closed by one pain message, If gate is closed by one pain message,

other messages may not be able to pass other messages may not be able to pass through through

Controlling PainControlling Pain

►Fear, or high levels of anxiety, almost Fear, or high levels of anxiety, almost always increase painalways increase pain

► If you can regulate a painful stimulus, If you can regulate a painful stimulus, you have control over ityou have control over it

►Distraction can also significantly Distraction can also significantly reduce painreduce pain

►The interpretation you give a stimulus The interpretation you give a stimulus also affects painalso affects pain

Coping With PainCoping With Pain

►Prepared Childbirth Training: Promotes Prepared Childbirth Training: Promotes birth with a minimal amount of drugs birth with a minimal amount of drugs or painkillersor painkillers

►Counterirritation: Using mild pain to Counterirritation: Using mild pain to block more intense or long-lasting painblock more intense or long-lasting pain