Unit IV Sensation and Perception - PowerPoint Presentation

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Unit IV

Sensation and Perception

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Introduction

Sensation

The

process by which our sensory receptors and nervous system receive and represent stimulus energies from our

environmentPerceptionThe process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and eventsThey are one continuous process

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Introduction

Top-down processing

Constructs perceptions from the sensory input by drawing on our experience and expectations

We process this way when we HAVE prior knowledge, we start at the top and work down

Bottom-up processingStarts at the sensory receptors and works up to higher levels of processingWe process this way when we LACK prior knowledge, we start at the bottom and work our way up

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Top-Down Processing Example

“

I

cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the hmuan mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it

dseno’t mtaetr in waht oerdr the ltteres in a wrod are, the olny iproamtnt tihng is

taht

the

frsit

and

lsat

ltteer

be in the

rghi

t

pclae

. The

rset

can be a

taotl

mses

and you can

sitll

raed

it

whotuit

a

pboerlm

.

Tihs

is

bcuseae

the

huamn

mnid

deos

not

raed

ervey

lteter

by

istlef

, but the

wrod

as a

wlohe

.

Azanmig

huh?

yaeh

and I

awlyas

tghuhot

slpeling

was

ipmorantt

!”

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How much information do we actually take in at once?

Selective Attention

The focusing of conscious awareness on a particular stimulus

Cocktail party

effectHow can you focus on a conversation when at a party?Selective Attention and AccidentsCell phone use and car accidents

Almost 80% of accidents occur due to distracted driving 1 out of every 4 car accidents in the United States is caused by texting and driving.Texting while driving is 6x more likely to cause an accident than driving drunk.

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Selective Attention

Inattentional

blindness

Failing

to see visible objects when our attention is directed elsewhereChange blindnessChange deafness/blindness-failing to notice a change visual or auditory in ones environment

Pop-outA stimulus that is so powerful/different that it

demands our

attention

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Riddle of the day

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Transduction

 Thresholds

Every second of every day our sensory systems convert one form of energy into another by…

Receiving stimulation

Transforming the stimulation into impulses Delivering that impulse to the brainThis process is known as transduction

Psychophysics(ex. difference threshold) The study of relationships between the physical characteristics of

stimuli, and

our psychological experience of

them

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Transduction

 Thresholds

Absolute

threshold--Gustav Fechner

Minimum stimulation that allows you to hear 50% of the timeSignal-detection theoryA theory predicting how and when we detect the presence of a faint stimulusRatio of “hits” to “false alarms

”Goal is to understand why different people respond to the same stimuli Example Hearing

tests in school

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Transduction

 Thresholds

Subliminal

Stimulation

Below threshold of conscious awarenessPriming the activationSubliminal persuasion

Much of our information processing occurs automatically, out of sight off the radar of our conscious mindDifference thresholdJust noticeable difference Weber’s

Law

The principle that, to be perceived as different, two stimuli must differ by a constant percentage (rather than a constant

amount, roughly

a 2%

difference)

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Transduction

 Thresholds

Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation

Informative changesWe perceive the world not exactly as it is, but as it is useful to perceive it We are extremely sensitive to change anywherePeopleTV

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Practice FRQ…quick write

Mr. Zalewski is planning a ski trip for winter break. Define absolute threshold and difference threshold, and explain how each one might play a role in his perception of the winter weather he will experience.

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Vision

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The Stimulus Input: Light

Energy

Transduction (transform)

Conversion of one form of energy into

anotherWe take light and transform it into neural messagesWavelengthThe distance from the peak of one light or sound wave to the peak of the nextHue (color)

The dimension of color that is determined by the wavelength of lightIntensityWave amplitudeThe amount of energy in a light or sound wave, which we perceive as brightness or loudness

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The Physical Property of Waves

Shortwave=High frequency(Blueish colors)

Great amplitude(bright colors)

Long waves=low frequency(reddish colors

)

Small amplitude(dull colors)

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The Eye

Cornea

The

transparent layer forming the front of the eye.

PupilThe adjustable opening in the center of the eye through which lights entersIrisA ring of muscle tissue that forms the colored portion of the eye

LensThe transparent structure behind the pupil that changes shape to help focus Accommodation: Ability of the pupil to change shape/sizeRetina

The

light-sensitive inner surface

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The Eye

If you could follow light into the eye and through the retina…you would find buried in receptor cells,

Rods and Cones

Retinal

receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don’t respond(Rods)Retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations(cones)

Rods

Cones

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The Eye

Within the

r

etina

Optic nerveCarries nerve impulses to the brainBlind spotThe point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.Fovea

The central focal point in the retina, around which the eye’s cones cluster

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How do the eyes and brain process visual information?

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Visual Information Processing

Feature

detectors

Nerve

cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movementParallel processingThe processing of many aspects of a problem simultaneously

Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.Though it sounds odd, it is important to remember that you see as much with your brain as you do with your eyes

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Color Vision

“If no one sees an apple…is it red?”

First thing to understand a apple is EVERY color but red, it reflects(rejects) the long wavelengths of red

Second color resides solely in our brain

This is why we dream in color not in black and whiteThe Giver

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Color Vision

Young-Helmholtz trichromatic (three color) theory

The theory that

that people with normal color vision need

3 wavelengths of light to create different colorsThis theory explains how color vision works at the receptor level

Red – Green – BlueFor example we don’t have receptors for yellow instead we see yellow when we mix red and green conesMonochromatic vision

Complete

color blindness

Dichromatic

vision(This is what dogs have)

Is

a color vision defect in which one of the three basic color mechanisms is absent or not functioning

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Color Vision

Afterimage

When image continuing to appear in one's vision after the exposure to the original image has ceased

Opponent-process

theory

The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color visionCan only detect the presence of one color at a time because the two colors oppose one

another

You

do not see greenish-red because the opponent cells can only detect one of these colors at a

time

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The

Dress

For about half of us, the brain discounts the blue side of the light source, subtracting out the blue from the actual color of the dress so that we perceive the dress as white and gold. For the rest of us, the brain discounts the gold spectrum of the light, yielding a totally different perception of the dress as that of a blue and black dress.

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Can you trust your Eyes

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Introduction

Gestalt (form

or whole

)

Gestalt psychologist emphasized our tendency to integrate pieces of information into meaningful wholesThese psychologists demonstrated many principles we use to organize our sensations into perceptions Our brain does more than register information about the world

The Necker Cube

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Form

Perception

Figure

and GroundThe organization of the visual field into objects(the figure) that stands out from their surroundings (the ground)

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Form Perception

Grouping

Grouping

 The tendency to organize stimuli into coherent groupsProximitySimilarityContinuity

ConnectednessClosure

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Form Perception

Grouping

-

Proximity

We see three sets of two lines instead of 6 separate lines.

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Form Perception

Grouping

-

Similarity

We group similar figures together, we see the tringles and circles as vertical columns of similar shapes. Not horizontal rows of dissimilar shapes

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Form Perception

Grouping

-

Continuity

We perceive smooth continuous patterns, not ones that suddenly stop/are intersected

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Form Perception

Grouping

-

Connectedness

Because they are uniform and linked we perceive each set of two dots and the line between them as a single unit

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Form Perception

Grouping

-

Closure

We fill gaps to complete an object as whole

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Depth Perception

Binocular

Cues

Depth perceptionVisual-cliffBinocular cuesJudging the distance of nearby objects Our eyes are roughly 2 ½ inches apart giving us two different images of the world

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How do we perceive motion, depth, size and color?

Bring textbooks to class on Thursday

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Motion Perception

Our brains compute motion mostly based on the idea that shrinking objects are moving away, and growing objects are approaching

This is imperfect as sometimes larger objects appear to be moving slower and vise versa

Phi

phenomenonAn illusion of movement created when two or more adjacent lights blink on and off in quick succession

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Depth Perception

Monocular

depth clues help to make the world a more visually interesting place

Binocular cues focuses on 

depth, while monocular cues

focuses on size Relative heightRelative sizeInterposition

Linear perspective

Relative motion

Light and

shadow

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Depth

Perception

Monocular

Cues –

Relative Height

We perceive objects higher in our vision field as father away and vise

versa

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Depth

Perception Monocular Cues –

Relative Size

A

perceptual clue which allows you to determine how close objects are to an

object of known size…this can backfire

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Depth

Perception

Monocular

Cues -

Interposition

If one object blocks another we perceive it as closer to us

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Depth

Perception

Monocular

Cues –

Linear Perspective

Parallel lines appear to converge with distance. The more they cover the greater their perceived distance

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Depth

Perception

Monocular

Cues –

Relative Motion

As we move objects that are in fact stable may in fact appear to move with us

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Depth

Perception Monocular Cues –

Light

and Shadow

Nearby objects reflect more light. When given two identical shapes the dimmer one seems farther away, it also produces a sense of depth

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What changes while it stays the same?

Perceptual constancy

This is a top down process of perceiving

objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change

Shape constancyWe perceive a familiar object like a door as constant, even as it seems to change with our angle of view

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Perceptual Constancy

Size

Constancy

We perceive objects as having a constant size even when their distance varies Moon illusionIs an optical illusion which causes the Moon to appear roughly 50% larger near the horizon than it does higher up in the sky

Ponzo illusionIt was suggested that the human mind judges an object's size based on its background.

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Perceptual Constancy

Lightness

Constancy

Color does not reside in an object it depends on contextColor constancyWe perceive objects as having a constant color even as light shifts Lightness/Brightness

constancyWe perceive objects as having a constant lightness even when illumination varies It can be more difficult to ID differences

 mismatches

Relative

luminance

The amount of light an object reflects

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Ames Room

 A distorted room that is used to create an optical illusion based on size

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Perceptual Interpretation

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Visual Perception

Sensory Deprivation and Restored

Vision

What would happen if a person born blind then gained their sight as an adult?

People who gain sight lack the experience to visually recognize shapes, forms and facesWithout early stimulation the brain’s neural organization does not develop normally Our eyes can adjust…even if initially disoriented we mange to adapt.If you were to wear the “sensory deprivation goggles” long enough eventually your vision would adapt

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Perceptual Set

Perceptual set

A

mental disposition to perceive one thing and not another

Mental predispositionContext effectsHeight and weight is often contextual Motivation/ Emotions have a large effect

on perception

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Perception

is a

Biopsychosocial Phenomenon

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Is There Extrasensory Perception?

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Claims of ESP

Extrasensory

Perception

Telepathy

Mind to mind communication ClairvoyancePerceiving remote events PrecognitionPerceiving the future Psychokinesis (PK)“mind control”

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Premonitions or Pretensions

?

Psychic predictions

Nostradamus

 Psychic/coincidence ESP ExperimentsMillion dollar proposals

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Hearing

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The Stimulus Input: Sound

Waves

Audition

The sense/act of hearing

AmplitudeLoudnessFrequencyThe number of complete wavelengths that pass a point in a given time PitchA tone’s experienced highness or lowness; depends on frequency

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The

Ear

Outer ear

Channels the waves through the Auditory canal

 Ear drum causing it to vibrateMiddle EarHas three tiny bones(hammer, anvil and stirrup) that pick up the vibrations and transport them to the cochlea(located in the inner ear)

Inner EarThe cochlea triggers a nerve impulse that is sent to the Auditory nerve, which sends

information

to the auditory cortex in

the

brain...and boom we hear!

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The Ear

Perceiving Pitch and Sound

Place

theory(Theory 1)Explains how we hear high pitched

soundsProposes that our brain interprets pitch by decoding the place where a sound wave stimulates the basilar membrane Frequency theory(Theory 2)

Low

pitched

sounds

Proposes that the brain deciphers the frequency of the neural impulses traveling up the auditory nerve to the brain

Volley

principle, or the ability to match the frequency of a tone, thus enabling us to sense pitch

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The Ear

Perceiving Pitch and Sound

How do we locate sound?

The location of our ears allows us to enjoy Stereophonic Hearing(3-D)This is usually achieved by using two or more independent audio channels through a configuration of two or more loudspeakersLocalization of soundsIntensity/Speed of the sound

If a car honks on our right side it is louder and gets to our right ear faster, though the lag time is small it is enough for our body to react

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Hearing Loss and Deaf

Culture

Hearing loss

Conduction hearing loss

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochleaHas the ability to be repaired/can still hear slight sounds Sensorineural hearing lossHearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafnessPermanent deafness

Cochlea implantSigning

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Other Senses

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Touch

Types of touch

Pressure

Warmth

ColdPainSensation of hotRubber hand illusion

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Understanding Pain

Biological

Influences



NociceptorsGate-control theoryThe theory that the spinal cord contains a neurological “gate” that blocks or allows pain signals to the brain.

The “gate” is opened by pain signals traveling up the nerve fibers and is closed by activity in larger fibers or by information coming from the brain

Endorphins

Phantom limb sensations

Tinnitus-

ringing in ones ears

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Understanding Pain

Psychological Influences

Rubber-hand illusion

Memories or perceptions

of painSocial-Cultural InfluencesPresence of othersEmpathy for others painCultural expectations Controlling pain can occur a number of ways

Physical methods PTPsychological methodsA placebo can be as effective as some medicines

Distraction

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Taste

Sweet, sour, salty and bitter

Umami(savory)

Taste buds

Chemical sense

Taste buds reproduce every two weeks Age and taste

Number of taste buds/sensitivity decreases

Alcohol/ tobacco also effects this

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Where do taste and smell meet?

Sensory interaction

Interaction of smell and taste

Hold your nose, close your eyes and have someone feed you various foods

Could you tell the difference between an apple slice or raw potato McGurk EffectInteraction of other sensesBar/Far phenomenon

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Smell

Olfaction(smell)

Chemical sense

Taste and smell

Odor moleculesOlfactory bulbIs a neural structure of the vertebrate forebrain involved in the sense of smell.Olfactory nerveTransmits impulses to the brain from the smell receptors in the mucous membrane of the nose

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Can you tell the difference?

Can we tell if a person is male or female on the basis of odor alone?

Patricia Wallace had blindfolded subjects sniff a washed hand held ½ inch from their nose. Her subjects could discriminate between male and female with over 80% accuracy. Female sniffers identified at a more accurate rate than male.

Mark

Russel had college freshman wear T-Shirts for 24 hours after which the shirts were individually placed in sealed containers. Each subject then was presented with 3 containers-one holding his/her shirt the second an unknown male and the third and unknown female. The vast majority were able to ID their own shirt and which belonged to the male and female respectively

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