UNIT 6 - SENSATION & PERCEPTION PPT 10.30.12.pptx

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UNIT 6: SENSATION & PERCEPTION

Intro

• _{Prosopagnosia – face} blindness

– Perfect Vision = Sensation

– Face Blindness = Perception

• _{In the brain, an area in the}

underside of the right hemisphere allows us to

recognize human faces (takes us 1/7 of a second)

Basic Principles

• _{Bottom-Up Processing –}

begins with sensory receptors and works up to brain’s

integration of sensory information

• _{Top-Down Processing –}

guided by higher level mental processes; when we construct perceptions based on

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UNIT 6: SENSATION & PERCEPTION

• _{Our ears are most sensitive} to sound frequencies that include human voice

consonants and baby’s cry

• _{Sensitivity to high-pitched} sounds declines with age

• _{Absolute Threshold –} minimum stimulation necessary to detect a particular light, sound,

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UNIT 6: SENSATION & PERCEPTION

• _{Signal Detection Theory –} theory that predicts

how/when we detect

presence of a faint stimulus (signal) amid background stimulation (noise)

– Says there is NO single absolute threshold

– Detection depends on experience, motivation,

expectations, level of fatigue

• _{New parents may hear the} faintest sounds of their baby, but miss out on hearing louder, less meaningful noises

• _{Soldiers during wartime} • _{Video game playing may}

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UNIT 6: SENSATION & PERCEPTION

• Subliminal – below one’s absolute threshold for conscious awareness

– _{Yes, we can be affected by these}

stimuli; we do pick them up some of the time

– _{No, advertisers usually cannot}

influence us with “hidden persuasion”

• In study of self-esteem and memory, student scores revealed NO affect from subliminal stimulation

• _{Difference Threshold – (just} noticeable difference or jnd) – minimum difference a person can detect between any two stimuli 50% of the time

• _{Weber’s Law – for a difference} to be perceptible, two stimuli must differ by a constant

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UNIT 6: SENSATION & PERCEPTION

Sensory Adaptation

• _{Sensory Adaptation – our} diminishing sensitivity to an unchanging stimulus

– Eyes are always moving, or else they would miss some of the information in our field of vision

– We are alert to changes in our environment, but sensitivity “bores” with unchanging stimuli

Vision

• _{Transduction – conversion} of one form of energy into another; transforming

sights, sounds, smells into neural impulses our brain can interpret

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UNIT 6: SENSATION & PERCEPTION

Vision

• _{Wavelength – distance from} one peak to the next peak; determines hue(color)

• _{Amplitude – height of each} wave; determines intensity and brightness

• _{Vision happens as we} receive light waves

Vision

• _{The Eye (from outside to} inside – the path of light)

– Cornea – Iris

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UNIT 6: SENSATION & PERCEPTION

Vision

1. Cornea – protects eye and bends light to provide focus 2. Iris – colored muscle

surrounding the pupil; it

adjusts light intake by dilating or constricting to control the size of pupil opening

3. Pupil – adjustable opening in center of eye through which light enters

Vision

4. Lens – transparent structure

behind pupil that changes shape to help focus image on retina 5. Retina – light-sensitive inner

surface of eye, containing rods and cones, plus layers of

neurons that begin processing visual information

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UNIT 6: SENSATION & PERCEPTION

Vision

• _{Rods – in retina, detect}

black, white, gray; used for peripheral and twilight

vision; dim light • _{Cones – in retina,}

concentrated near center, function in daylight or well lit conditions; detect detail and colors

Vision

• _{Optic Nerve – nerve that} carries neural impulses from eye to brain

• _{Blind Spot – point where} optic nerve leaves the eye; no receptor cells there,

leaving blind spot

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UNIT 6: SENSATION & PERCEPTION

Visual Information Processing

• _{From optic nerve, visual}

information travels to visual area of thalamus (sensory switchboard), then on to the visual cortex in the occipital lobe at back of brain

Visual Information Processing

• _{Feature Detectors – nerve} cells in brain that respond to specific features of a stimulus, such as shape, angle, or movement

• _{Discovered by}_{David Hubel} and Torsten Wiesel (1979) • _{Cluster in temporal lobe}

behind right ear allows us to

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UNIT 6: SENSATION & PERCEPTION

Parallel Processing

• _{Parallel Processing – doing} many things at once; like our brain

• _{Serial Processing –} step-by-step; like most computers • _{Blindsight – localized area of}

blindness in part of the visual field

– Patient is NOT aware of seeing stimulus, but may accurately make predictions about it

Color Vision

• _{Objects do NOT possess} color; color resides in our brains

– A “red” tomato is everything but red, as it reflects the long wavelengths of red

– 1 out of every 50 people is color deficient

• _{Usually male}

• _{Defect is genetically}

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UNIT 6: SENSATION & PERCEPTION

Color Vision

• _{Young-Helmholtz}

trichromatic (3-color) theory

– Retina contains red, green, and blue color receptors – When stimulated in

combination, they produce the perception of any color

Color Vision

• _{Opponent-Process theory}

– Opposing retinal processes enable color vision

• _Red-Green • _Yellow-Blue • White-Black

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UNIT 6: SENSATION & PERCEPTION

Color Vision

• _{Color-Deficient – these} people are not actually

blind to color; they simply lack functioning red- or green- sensitive cones, or both

– Monochromatic = one color – Dichromatic = two colors

Color Vision

• _{Afterimages – confirm Ewald} Hering’s opponent-process theory

– Red-Green

– Yellow-Blue

– White-Black

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UNIT 6: SENSATION & PERCEPTION

Hearing

• _{More of the brain cortex is} devoted to vision than any other sense

• _{Audition = hearing}

• _{Ears detect air pressure} changes and can also feel the vibrations of some sounds

Hearing

• _{Amplitude = strength or} loudness

• _{Frequency = pitch}

• _{Decibels = units used to} measure sound

– _{Every 10 decibel increase is}

equal to 10x increase in sound intensity

– _{60 decibels is 10,000 times}

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UNIT 6: SENSATION & PERCEPTION

The Hearing Process

1. Outer ear channels sound waves through auditory canal to eardrum

– _{Eardrum is a tight membrane}

that vibrates with the waves 2. Middle ear transfers

vibrations from eardrum through a piston (hammer, anvil, stirrup) to the cochlea

– _{Cochlea is snail-shaped tube in}

inner ear

The Hearing Process

3. Membrane (oval window) on cochlea vibrates, moving the fluid in the tube

4. Movement of fluid causes ripples in the basilar membrane (hair cells that bend)

5. Hair cells trigger impulses in adjacent nerves, which lead to the auditory nerve

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UNIT 6: SENSATION & PERCEPTION

Hearing

• _{If we cannot talk over a} noise, it is potentially harmful to our ears • _Ringing_{of the ears is}

hearing’s equivalent to bleeding; it indicates possible hearing damage

• _{Men’s hearing is less acute} than women’s

Hearing

• _{Brain can interpret}_loudness from the number of

activated hair cells • _When_{hair cells lose}

sensitivity to soft sounds, they may still be as

responsive to loud sounds • _{Prolonged exposure to}

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UNIT 6: SENSATION & PERCEPTION

Hearing

• _{Place Theory – in hearing,} links pitch we hear with the place where the cochlea’s membrane is stimulated • _{Frequency Theory – in}

hearing, the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone,

enabling us to sense pitch

Hearing

• _{Place Theory – helps explain} high-pitched sounds

• _{Frequency Theory – helps} explain low-pitched sounds • _{Volley Principle – when}

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UNIT 6: SENSATION & PERCEPTION

Locating Sounds

• _{Sound travels at 750 mph} • _{Sound waves strike one ear}

sooner and more intensely than the other; helps locate direction of sound

• _{Sounds equidistant from}

both ears are tough to locate • _{To pinpoint a sound, we tilt}

our head to allow sound to read one ear first

Hearing Loss & Deafness

• _{Conduction Hearing Loss}

– _{Damage to mechanical system}

that conducts sound waves to cochlea

• _{Sensorineural Hearing Loss}

– _{Damage to cochlea’s receptor}

cells or to the auditory nerves; also called nerve deafness

• _{Cochlear Implant}

– _{uses electrical signals to}

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UNIT 6: SENSATION & PERCEPTION

Other Important Senses

• _{People who lose one} channel of sensation do compensate with a slight enhancement of other sensory abilities

Other Important Senses

• _{Vision (most cortical space)} • _{Hearing (next most…)}

• _Touch

• _{Body Position & Movement} • _Taste

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UNIT 6: SENSATION & PERCEPTION

Touch

• _{Touch is essential to} development

– _{Baby monkeys not allowed to}

touch their mother become very unhappy

• _{Some spots on skin are} especially sensitive to

pressure, warmth, cold, & pain

– _{Pressure is only sensation with}

identifiable receptors; the rest are the same

Touch

• _{A tickle from someone else} produces MORE

somatosensory cortex activation than one from self

– _{Brain is wise enough to be} most sensitive to unexpected stimuli

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UNIT 6: SENSATION & PERCEPTION

Touch

• _{Warm & Cold water hoses} wound around each other produce sensation of hot • _{Rubber hand illusion}

produces sensation of warmth for most people

– This is top-down processing

Position & Movement

• _{Kinesthesis – system for} sensing the position and movement of individual body parts

– _{Vision interacts with this}

• _{Vestibular Sense – the sense} of body movement and

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UNIT 6: SENSATION & PERCEPTION

Position & Movement

• _{Ian Waterman}

(proprioception video) – lost functioning of sensory neurons; feels disembodied, as though body is dead or not real; reinforces that vision interacts with

kinesthesis

Position & Movement • _{Vestibular Sense}

– _{Semicircular Canals and}

Vestibular Sacs contain fluid that moves when your head tilts or rotates

– _{Movement stimulates hair-like}

receptors which send message to cerebellum, enabling sense of body position and balance

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UNIT 6: SENSATION & PERCEPTION

Pain

• _{“Pain Protects Us” – it is our} body’s way of telling us

something has gone wrong

– _{Some individuals are born}

without the ability to perceive pain (opposite is true too)

– _{Many times these individuals}

suffer severe injury or death prior to adulthood

• _{This happens as a result of}

accumulated strain on body

Pain

• _{Nociceptors – sensory} receptors that detect hurtful temperatures, pressure, chemicals

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UNIT 6: SENSATION & PERCEPTION

Pain

• _{Gate-Control Theory –} spinal cord contains a neurological “gate” that blocks pain signals and allows them to pass on to the brain

– Gate is opened by pain signals traveling up small nerve fibers – Gate is closed by activity in

larger fibers or by info. coming from the brain

Pain

• _{Distraction from pain plus} the release of endorphins can greatly diminish

sensation of pain

• _{Brain can also “create” pain,} as exemplified by the

phantom limb phenomenon

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UNIT 6: SENSATION & PERCEPTION

Pain

• _{Tinnitus – phantom sounds} experienced by those with hearing loss; ringing sound • _{Hallucinations – phantom}

sights experienced by those with vision loss

• _{Phantom tastes and smells} also exist

– _{All these examples illustrate}

the brain is prewired to experience sensation

Pain

• _{We edit our memories of} pain

– We tend to remember pain’s peak moment

– We register pain based on the amount we feel at the end of the experience

• _{When pain lasts longer, but}

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UNIT 6: SENSATION & PERCEPTION

Pain

• _{We tend to perceive more} pain when others also seem to be experiencing pain

(social effect)

• _{When feeling empathy for} another’s pain, a person’s own brain activity may partly mirror that of the other’s brain in pain

Controlling Pain

• _{Physical & Psychological} Methods

– Drugs

– Surgery

– _Acupuncture

– Electrical Stimulation

– Massage

– Exercise

– Hypnosis

– Relaxation Training

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UNIT 6: SENSATION & PERCEPTION

Controlling Pain

• _{Giving fake pain-killing}

chemicals may help body to release real ones

• _{Drawing attention away} from pain with “pleasant images” is an effective way to increase pain tolerance • _{Pain is “in the brain”, so}

diverting attention away can bring relief

Taste

• _{Sweet, Sour, Salty, Bitter}

• _Umami

– Savory, meaty taste

• _{Tastes have evolutionary} background

– Good tastes led to energy- and protein-rich foods

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UNIT 6: SENSATION & PERCEPTION

Taste

• Taste is a chemical sense • _{Receptors in taste buds are}

specialized to respond to different tastes

• _{Taste receptors reproduce} every few weeks

• _{As we grow older, number of} taste receptors decreases

• _{Expectations of tastes}

influence our brain’s response

Taste

• _{Sensory Interaction}

– Smell + Texture + Taste = Flavor

• _{McGurk Effect}

– Seeing the mouth movements for “ga” while hearing “ba” we may perceive “da”

– _{Illustrates that our senses interact}

• _{Synaesthesia – rare}

phenomenon where senses become joined

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UNIT 6: SENSATION & PERCEPTION

Smell

• _{Smell = Olfaction or your} Olfactory Sense

• _{Smell is a chemical sense}

– _{Approximately 350 receptor}

proteins work to recognize particular odor molecules

– _{Odors trigger a combination of}

receptors, triggering smell • _{Human’s senses of seeing}

and hearing are better than our sense of smell

Step-By-Step Smell

1. Airborne molecules reach receptors at top of nose

2. Receptor cells send messages to the brain’s olfactory bulb 3. Message moves on to

temporal lobe – specifically the primary smell cortex

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UNIT 6: SENSATION & PERCEPTION

Smell

• _{Women and young adults} have best sense of smell • _{Smells are very difficult to}

describe and recall

• _{Animals with heightened} sense of smell have more olfactory receptors

Smell

• _{We associate smells with} experiences

– Smell associated with a

positive prior experience will lead us to like that smell

• _{Even though smells are}

tough to describe, smells do evoke feelings and

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UNIT 6: SENSATION & PERCEPTION

Perceptual Organization

• _{Gestalt – an organized} whole; a German word meaning form or whole

– Gestalt psychologists

emphasized our tendency to integrate pieces of

information into meaningful wholes

Perceptual Organization

• _{Gestalt psychologists say} that the “whole may exceed the sum of its parts”

– Sodium = a corrosive metal – Chlorine = poisonous gas

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UNIT 6: SENSATION & PERCEPTION

Figure and Ground

• _{Figure-Ground – the}

organization of the visual field into objects (figures) that stand out from their surroundings (the ground)

– _{Sometimes figure and ground} are reversible, as in the

picture on page 264 of text

Grouping Principles (pg. 265)

• _Proximity

• _Similarity

• _Continuity

• _{Connectedness}

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UNIT 6: SENSATION & PERCEPTION

Depth Perception

• _{Depth Perception – seeing} objects in 3-dimensions

enables us to estimate their distance from us

• _{Visual Cliff – a laboratory} device for testing depth perception in infants and young animals

– _{Most will NOT crawl over the}

visual cliff; illustrates they have depth perception

• _{By the time we become} mobile, we have the depth perception we need to

survive

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UNIT 6: SENSATION & PERCEPTION

• _{Binocular Cues – depth} cues, such as retinal

disparity, that depend on two eyes

– _{Our eyes are 2.5 inches apart} – _{Difference between images in}

either eye is retinal disparity – _{Makers of 3-D movies use}

concept of retinal disparity by using 2 cameras to film the same scene (like eyes)

• _{Monocular Cues – depth} cues, such as interposition and linear perspective,

available to either eye alone

– _{Relative height – we perceive} vertical dimensions as longer than identical horizontal

dimensions

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UNIT 6: SENSATION & PERCEPTION

• _{Other Monocular Cues} (pg 268)

– Relative height – Relative size – Interposition

– Linear Perspective – Light & Shadow – Relative Motion

Motion Perception

• _{Brain computes motion}

– Shrinking objects are retreating

– Enlarging objects are approaching

– Large objects appear to move slower than smaller objects at the same speed

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UNIT 6: SENSATION & PERCEPTION

Motion Perception

• _{Phi Phenomenon – an}

illusion of movement when two adjacent lights blink on and off in quick succession

– _{Strings of Christmas lights} – _{Marquee signs}

Perceptual Constancy

• _{Perceptual Constancy –} perceiving objects as unchanging (having

consistent shapes, size,

lightness, and color) even as illumination and retinal

images change

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UNIT 6: SENSATION & PERCEPTION

Size Illusions

• _{Moon Illusion – the moon} appears much larger as it is closer to the horizon, and smaller as it rises in the sky • _{Ames Room Illusion –}

trapezoidal room is viewed by one eye; room appears normal with two very

differently sized people in it

Lightness Constancy

• _{Lightness Constancy}

(Brightness Constancy) – we perceive an object as having a constant lightness even while its illumination varies • _{Relative Luminance – the}

amount of light an object reflects to its surroundings

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UNIT 6: SENSATION & PERCEPTION

Color Constancy

• _{Color Constancy –}

perceiving familiar objects as having consistent color, even if changing

illumination alters the wavelengths reflected by the object

Perceptual Interpretation

• _{Immanual Kant (1724-1804) –} German philosopher who

said knowledge comes from our inborn ways of organizing sensory experiences

• _{John Locke (1632-1704) –} British philosopher who said that it is through our

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UNIT 6: SENSATION & PERCEPTION

Sensory Deprivation & Restored Vision

• _{Situation: A man born blind} learns difference between a sphere and a cube by touch. With restored vision, is the man able to visually

discriminate between the two?

• _{Answer: No, the man would} have never learned to see the difference

Sensory Deprivation & Restored Vision

• _{Retinas still relayed signals} to the visual cortex (in this situation)

• _{Lacking earlier stimulation,} the cortical cells did not

develop normal connections • _{There IS a critical period for}

normal sensory and

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UNIT 6: SENSATION & PERCEPTION

Perceptual Adaptation

• _{Perceptual Adaptation – in} vision, the ability to adjust to an artificially displaced or even inverted visual field

– Perception Goggles

• Humans make the adjustment to the new visual field; chicks do NOT

• Humans quickly adjust back after goggles are off

• _{Brain does NOT eventually}

switch to “upside down” view;

Perceptual Set

• _{Perceptual Set – a mental} predisposition to perceive one thing and not another

– Experiences, assumptions, expectations give us a “top-down” predisposition

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UNIT 6: SENSATION & PERCEPTION

Perceptual Set

• _{Loch Ness Monster or a log} • _{Perceptual sets also effect}

what we hear

– _{Pilot to depressed co-pilot,} “gear-up” rather than “cheer up”

• _{Young kids like french fries} better when served in a McDonald’s bag

Forming Perceptual Sets

• _{Through experience, we} form concepts (or schemas)

• _{Sometimes faces shown in} caricature (emphasizing certain details) are more

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UNIT 6: SENSATION & PERCEPTION

Context Effects

• _{When a 6’9” basketball}

player stands next to a 7’9” player, the first player

appears short; in reality, he is tall

• _{When we see a newborn}

clothed in pink, we

generally recognize more feminine characteristics about the baby

Emotion & Motivation

• _{If motivated to see a} particular object in an

ambiguous set, we are more likely to see that object

• _{When driving, we are} stressed by pedestrians; when walking, we are stressed by drivers

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UNIT 6: SENSATION & PERCEPTION

Perception & the Human Factor

• _{Human Factors Psychology –} explores how people and machines interact, and how machines and physical

environments can be made safe and easy to use.

– Examples include:

• _{Ideal kitchen layout} • Sales ideas for stores

• Landing tips for pilots

Perception & the Human Factor

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UNIT 6: SENSATION & PERCEPTION

Extrasensory Perception

• _{ESP (extrasensory perception)} – controversial claim that

perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition

• _{Parapsychology – the study of} paranormal phenomena,

including ESP and psychokinesis

Extrasensory Perception • _{Telepathy – mind-to-mind}

communication

• _{Clairvoyance – perceiving} remote events, like sensing a friend’s house is on fire

• _{Precognition – perceiving} future events

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UNIT 6: SENSATION & PERCEPTION

• _{“A person who talks a lot is} sometimes right.”

– Spanish Proverb

– _{No scientific evidence that} any ESP actually works

– _{35% of U.S. police depts. have} at one time used psychics; none found it helpful

– _{Vague predictions can later} be retrofitted to make them seem meaningful

– _{Billions of events happen in} the world daily; given enough days virtually anything is

possible somewhere

– $1 million offer still stands for scientific proof that ESP is real; not one person has claimed it yet