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Myers’ PSYCHOLOGY

(6th Ed)

Chapter 5

Sensation

James A. McCubbin, PhDClemson University

Worth Publishers

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CH. 5: Sensation

Sensation: process by which sensory receptors + nervous system receive & represent stimulus energy

- stimulation of neurons in sensory nerves, such as optical & auditory nerves…creating action potential

Perception: the way we organize & interpret sensory info, enabling us to recognize meaningful objects & events

-helps us to “know” what something is…as long as we have experience with it

-prosopagnosia: visual condition -can receive stimulus, but cannot organize

it into recognizable things…so can’t recognize it

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Sensory & perceptual processes work together to help us sort out complex processes “The Forest Has Eyes…”

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Sensation Bottom-Up Processing: sensory analysis

that begins w/ sense receptors then brain’s

integration of sensory info -neural signals into action potentials Top-Down Processing: info processing

guided by higher-level mental processes as when we construct perceptions drawing

on our experience & expectations…often what we are used to seeing…&

---what we expect to seeEX: prosopagnosia: receiving signals

(sensory) & ID facial features, but can’t put it together& name them…but can feel emotional reaction…see son, warm emotions, but no recognition…

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Sensation- Basic Principles Thresholds: “How low can you go?”

Psychophysics study of the relationship between

physical characteristics relate to our psychological experience …how intense? How is it changing?

Light- brightness Sound- volume Pressure- weight Taste- sweetness

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Sensation- Thresholds Absolute Threshold: minimum stimulation

needed to detect a particular stimulus 50%

of the time

EX: the earphones used in a hearing test… -vision: if we are on top of a mtn., we

can see a candle flame on another mtn. 30 miles away (if it is a dark, clear night)

-touch: wing of a bee on our cheek -smell: 1 drop of perfume in a 3-rm. Apt.

Difference Threshold (197): minimum difference between two stimuli required for detection 50% of the time just noticeable difference (JND)

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Sensation- Thresholds Signal Detection Theory: predicts how & when we detect the presence of a faint stimulus

(signal) amid background stimulation (noise…meaning

distracting stuff around you…can be visual) assumes that there is no single absolute

threshold detection depends partly on person’s

Experience

expectations motivation level of fatigue -soldier’s awareness on guard duty? -mom’s can hear baby b/c tuned in to it --how about you & your cell phone??

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Sensation- Thresholds Subliminal: real or unreal? When stimuli are

just below one’s absolute threshold for conscious awareness, but can be perceived unconsciously

“EAT POPCORN?” Eliminate bad

habits, attain goals? Can have fleeting

effect…but not enduring

Expectations?(197) Now ads put info

into our minds—colors, “cool” in smoking…

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25

50

75

100

Low Absolutethreshold

Medium

Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

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Sensation- Thresholds Weber’s Law- to perceive as different, 2 stimuli

must differ by a constant minimum %…how much causes a JND? light intensity- for avg. person to tell a difference in 2

lights, difference must be at least 8% weight- 2% (5 lbs?) --tone frequency- 0.3% NOTE: these are rough approximations

-affected also by expectations & experience: 50 cent bar 5 cents? How much w/ $40,000 Mercedes?

Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

-after constant exposure to a stimulus, nerves fires

less frequently…odors, your watch, sounds…but not

vision b/c eyes continually move just slightly…but if

we held it constant?

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Vision- Stabilized Images on the Retina: If truly constant, vision does fade…

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Benefit of sensory adaptation: Though it reduces our sensitivity, it allows us to focus on new info coming into our environment

--we notice novelty…the new, the different…

Why is this important? “We perceive the world not as it is,

but as it is useful for us to perceive it.”

--Effect of TV…why does it hold our

attention so well?

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Vision: Transduction: conversion of 1 form of energy to another

in sensation, transforming stimulus energies into neural impulses (action potential)

In vision, light is transduced into neural messages (action potentials) from optic nerve to the brain

Wavelength: the distance from the peak of one wave to the peak of the next

--determines hue or color (lo- or hi- pitch in sound) Intensity: amount of energy in a wave determined

by amplitude…the height of the wavelength Brightness or dullness in colors loudness

Humans can only see part of the electromagnetic spectrum…Which can we not see?

But bees see ultraviolet (b-199)…snakes see infrared

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The spectrum of electromagnetic energy

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Vision- Physical Properties of Waves

Short wavelength=high frequency(bluish colors, high-pitched sounds)

Long wavelength=low frequency(reddish colors, low-pitched sounds)

Great amplitude…(bright colors, loud sounds)

Small amplitude(dull colors, soft sounds)

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Vision: How we transform physical energy into color, etc.:

Cornea- clear outer covering of the eye where light 1st enters

Pupil- adjustable opening in the center of the eye…light comes in from the cornea to

the pupil… Iris- a ring of muscle that forms the

colored portion of the eye around the pupil and controls the size of the pupil opening by contracting & expanding

Lens- transparent structure behind pupil that changes shape to focus images on the retina

--image comes in upside-down

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Vision

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Vision Accommodation- the way the eye’s lens changes shape to help focus near or far objects on the

retina Retina- the light-sensitive inner surface of the

eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

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Problems in vision: Acuity- the sharpness of vision: how well we

see Nearsightedness- condition in which nearby

objects are seen more clearly than distant objects because distant objects in front of retina (can see close, not far away) [myopia]

Farsightedness- faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

(hyperopia… aka hypermetropia)

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Vision: When it doesn’t work…

Farsighted Nearsighted Normal Vision Vision Vision

(elongated) (squatty) (round)

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Retina’s Reaction to Light- -Receptors:

Rods peripheral retina detect black, white and gray twilight or low light…use for night vision

Cones near center of retina fine detail and color vision daylight or well-lit conditions Fovea: concentration of cones on retina Blind spot: no rods or cones…

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Retina’s Reaction to Light

Optic nerve- nerve that carries neural

impulses from the eye to the brain Blind Spot- point at which the optic

nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there

Fovea- central point in the retina, around which the eye’s cones cluster

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1. Light hits retina (rods/cones) 2. fires bipolar cells…3. ganglion cells activate optic nerve

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Vision- Receptors

Receptors in the Human Eye

Cones Rods

Number

Location in retina

Sensitivity in dim light

Color sensitive? Yes

Low

Center

6 million

No

High

Periphery

120 million

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Pathways from Eyes to Visual Cortex: optic chiasm = cross-over point to opposite hemispheres

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Visual Info Processing: The work of D. Hubel & T. Wiesel: Feature Detectors

nerve cells in the visual cortex of the brain that respond to specific features (p. 204-205)

3 features: Shape… angle…movement…

Then info goes to special areas of temporal or parietal…faces? Houses? Chairs?

Begins w/ simple shapes & combine into more complex

fMRI used to ID where we look…at what we look

Stimulus

Cell’s responses

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How the Brain PerceivesChanging cube? (b-205) Stare at the cube… It will “change” every few seconds!

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Illusory (illusions) Contours: We fill in areas…Do you see a triangle?Psy not totally sure how all this works…are new research & theories on-going…

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Visual Info Processing (p. 206)

Parallel Processing: How our brain processes simultaneous processing of several aspects of a

problem simultaneously EX: Divides a visual scene into color, depth,

mov’t, form (shapes) & works on each at same time

Coordinates & combines info into perception computers = “serial” processing… step 1,2,3,…

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Visual Information Processing 2 Theories RE: how we see color: 1) Trichromatic (three color) Theory:

receptors for 3 & they “blend” (Young and Helmholtz) Think paint-mixing!

3 different retinal color receptors red green Blue

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Color-Deficient Vision

People who suffer “red-green color blindness” have trouble perceiving the number within the design

BUT…true “color blind – NO cones to process color

What we call C-B is actually color deficiency

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Visual Information Processing

2) Opponent-Process Theory- opposing retinal

processes enable color vision --certain # of each in “balance”…& if one goes

on, its opposite goes OFF…then they fire to come back into balance

“ON” “OFF”red greengreen red blue yellow yellow blue black whitewhite black

This causes an “afterimage”…remember the flag??

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Opponent Process- Afterimage Effect

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Focus on the 3 dots at the center of the picture

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Visual Information Processing

Color Constancy Perceiving familiar objects as having

consistent color, even if changing illumination alters the wavelengths reflected by the object

Also in vision, have brightness constancy, shape constancy, &

size constancy

These aspects depend on their surroundings

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I-D which is which type of constancy

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Audition: the sense of hearing

Amplitude: the loudness or intensity of sound, determined by the height of a sound wave (hi = bright color)

Frequency: the number of complete wavelengths that pass a point in a given time (hi-freq. colors = blue)

Pitch: a tone’s highness or lowness depends on frequency

Timbre: the quality of sound…how 1 voice differs from another , or a guitar differs from “C” on a piano

Decibels: measuring unit for sound energy; measures the amplitude

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The Intensity of Some Common Sounds: Decibels: the measure of amplitude (loudness) in sound

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Writing: p. 213…Read & respond to the following prompts:

1) 1st paragraph: Explain how sound waves are processed into sound

2) 2nd paragraph: Describe the cilia that are on the oval window & the basilar membrane on which the cilia are located.

-What is the dangers to these cilia? -What happens if they are damaged? -How can we protect them?

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Audition- The Ear Middle Ear

chamber between eardrum & cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window w/ basilar membrane inside.

Inner Ear innermost part of the ear, continuing the cochlea,

semicircular canals, and vestibular sacs Cochlea

coiled, bony, fluid-filled tube in the inner ear through which contains the basilar membrane

Basilar membrane: tissue in the cochlea; hair cells on the basilar membrane hold cilia…which are moved by vibrations…& this causes firing into the auditory nerve endings goes to auditory nerve to brain…

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How we perceive pitch: 2 theories:

1) Place Theory: says we hear different pitch b/c different sound waves trigger activity in different places along the cochlea’s membrane

-so the brain determines pitch by recognizing the place on the membrane from which it receives neural signals… EX: hi freq. = beginning of membrane; lo = end

--good at explaining high pitch, not so good at low

2) Frequency Theory: the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

--EX: If freq. = 100, then 100 pulses per sec. travel up the auditory nerve…but above 1000? It can’t do it…

--but volley principle says can alternate firing (like soldiers reloading)…

-Freq. theory is good for low, not so good for high...so both together seem to explain it all…

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How We Locate Sounds…& the “sound shadow”…Brain senses waves faster in closest ear & senses direction…loss of 1 ear = difficulty locating direction of sounds

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Audition: Hearing loss Conduction Hearing Loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea

Hearing aids can help; sometimes can be surgically repaired

Nerve Hearing Loss (Sensorineural) : hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve Cilia (receptor cells for hearing on basilar

membrane) are damaged…& as of now you cannot repair this loss, & hearing aids are of minimal benefit

Usually caused by exposure to loud sound or to constant sound …and also by aging

--can be caused by some diseases also

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Hearing Loss: Repairing sensori-neural hearing loss:

-hearing aids may help a bit -regenerating cells in other animals (sharks,

birds) led to in other animals—guinea pigs & rat pups

-scientists hope to be able to do the same in humans -can do a cochlear implant, a “bionic ear”, that

does get some sound info to the brain -can use on adults who lost hearing later & on

deaf kids…but not on adults who lost hearing as a young child & didn’t learn to process sound

Deaf Culture: some members of Nat. Assoc. of the Deaf argues you should not do this to kids…that deafness is NOT a disability…

Read p. 217…make a few notes about this (both sides of the argument) …what do you think? And we will discuss this…

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Cochlear implants

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Audition & ages… Older people tend to hear low frequencies well but suffer hearing loss for high frequencies navy line = 20-29; red = 30-39;

blue = 40-49; green = 50-59; yellow = 60+

1time

10times

100times

1000times

32 64 128 256 512 1024 2048 4096 8192 16384

Frequency of tone in waves per second

Low Pitch High

Amplitude required forperception relative to 20-29 year-old group

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Touch: Though vision & hearing = 2 major senses for humans, others are critical also major 4 Skin Sensations

pressure only skin sensation

with identifiable receptors

warmth cold Pain--these 4 processed w/

specialized nerve endings for each

-emotional ties thru touch as well as survival (babies?)

Why can we not tickle ourselves?

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Two different views of the sense of touch:

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Pain

Fast pain vs. slow pain receptors: slow = dull, throbbing; fast = sharp, intense

Phantom-limb pain: 7 out of 10 amputees feel pain or movement in a missing limb

-but other senses do this also…phantom sights in those who have lost sight, phantom hearing in those who have gone deaf

Gate-Control Theory: See Side 49 theory that the spinal cord contains a

neurological “gate” that blocks pain signals or allows them to pass on to the brain

“gate” opened by the activity of pain signals traveling up small nerve fibers

“gate” closed by activity in larger fibers or by information coming from the brain

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Notes RE: Pain Control:

Cold or competing stimulus (rubbing) can help w/ this (b-221)

Distraction lessens painEndorphins lessen (feel less pain after

phys. activity, like after a game?)Strong pain for short time is

remembered as worse than moderate pain for long time

Lamaze: breathing, relaxation, counter-stimulation (massage), distraction

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Taste Non-tasters vs. super-tasters: Taste Sensations

--sweet (most = sweet) --sour --salty --bitter

Bitter warns us of possible poisons Sensory Interaction

the principle that one sense may influence another

as when the smell of food influences its taste Each “bump” (papillae) contains up to 200

taste-buds which contain pores w/ receptors Sensory interaction: Taste interacts strongly w/

smell…& BOTH are “chemical senses” --smell + texture + taste = Flavor -we also have sensory interaction w/ sight +

sound: ”I hear better w/ my glasses on…”

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Taste:

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Smell: Olfaction…olfactory nerves --Other than knowing we do have olfactory receptors, actual way we smell is a mystery…It is a chemical sense like taste)

Receptor cells inolfactory membrane

Nasal passage

Olfactorybulb

Olfactorynerve

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Smell: Odor molecules can’t be broken down like light is in a spectrum…We recognize odors individually

Ability declines w/ age-Smell is primitive…&

evokes strong emotion

Less research on smell & taste b/c it is more subjective (vs. objective)

-We tend to give it “qualities”…spicy, etc., & these can vary from person to person

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Age, Sex and Sense of Smell

Women

Men

10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99Age Group

4

3

2

0

Numberof correct

answers

Women & young adults have best sense of smell

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Body Position & Movement Kinesthesis (mov’t)

The system for sensing the position & movement of individual body parts

We have position & motion sensors that are part of our skeletal & muscular systems

Interacts w/ vision Read p. 227, below “kines.” RE: Ian Waterman

Vestibular Sense: The sense of balance Monitors the head’s--& thus the body’s—position Interacts w/ kinesthesis Hair-like receptors in vestibular sacs sense when

fluid is out of balance Semi-circular canals & vestibular sacs in inner

ear Also aids body positioning & proper mov’t.

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Vestibular sense

organs:

•Head (& so body) position

•Balance•Movement