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Chapter 5 Sensation and Reality


Chapter 5 Sensation and Reality McElhaney – PowerPoint PPT presentation

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Title: Chapter 5 Sensation and Reality

Chapter 5 Sensation and Reality
  • McElhaney

AP Outline
  • Threshold
  • Absolute Threshold
  • Difference Threshold
  • Physical, Psychological, and physiological
    variables affected by thresholds
  • Signal Detection Theories
  • Absolute Threshold Theory
  • Sensory Receptors
  • Transduce of energy for nervous system
  • Anatomy,
  • Function,
  • Eye and ear
  • Color theories of vision
  • Audition
  • Perceptual acuity
  • Sensory adaptation
  • Sensory disorders
  • Deafness
  • Colorblindness
  • IV. Sensation and (79)
  • Thresholds
  • Sensory Mechanisms
  • Sensory Adaptation
  • Perception
  • Attention
  • Perceptual Processes

Sensation Data Reduction System
  • 5 senses work similarly
  • Select
  • Analyze
  • Filter
  • Process identifies meaningful information.

All of the Senses
  • Use Transduction
  • The process of changing energy (stimulus) to a
    form that can be processed by the nervous system-
  • For example- light to a form that can be
    recognized by the retina.

Sensory Analysis
  • As senses process information (from environment)
  • The senses divide the world into perceptual
    features- or basic stimulus patterns
  • Example
  • Vision features include lines, shapes, edges,
    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
Perceptual Features- Pop Out when a pattern is
Sensory Coding
  • After sense info is analyzed
  • It is converted to neural messages able to be
    understood by the brain.
  • Transduction

Sense Organs and Sense Localization
  • Eyes
  • Ears
  • Tongue
  • Nose
  • Skin
  • The type of sensation you experience
  • Depends on which brain area is activated
  • Vision
  • Auditory
  • Taste
  • Touch

All of the Senses include Concept of
  • Absolute Threshold
  • The minimum amount of energy necessary for
    sensation to occur.
  • This is after transduction-
  • Immediate response in the brain
  • Recall limits of senses Dog whistles- humans do
    not have awareness because they are below the
    minimum threshold of human awareness.
  • 40,000 hertz (hertz vibrations per second)

Difference Thresholds and JND
  • Q How much must a stimulus change before it is
    noticeably different?
  • JND Just Noticeable Difference
  • Just Noticeable Difference the change in
    stimulus intensity to be noticed between being
    noticed and not noticed.
  • Webers Law The amount of change needed to
    produce a constant JND is a constant proportion
    of the original stimulus intensity (See page 178)
    1 candle to increase need 10 more (Web Site)
  • Relates to Sensitivity ratios -hearing is much
    more sensitive than taste.

Perceptual Defense
  • Thresholds vary for different people and can
  • The resistance to perceiving threatening or
    disturbing stimuli Perceptual Defense
  • We resist info that causes anxiety, discomfort or

What is Subliminal Perception? Web video
  • Limen (threshold or limit) for awareness
  • Below the normal threshold Subliminal
  • Krosnick Study- emotional images inserted too
    fast to be recognized-
  • Caused altered impressions
  • Not really effective in advertising.
  • Vokey and Read study for Rock Music- Back
    messaging (had no known effect) (link)
  • Is Hypnopædia- Brave New World- is this

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Identify properties/function of Anatomy of the
  • Lens
  • Retina
  • Cornea
  • Fovea
  • Optic Nerve
  • Iris
  • Pupil
  • Blind Spot
  • Aqueous Humor
  • Vitreous Humor
  • Ciliary Muscle
  • Sclera
  • Cones
  • Rods

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Structure of Eye
  • Like a Camera
  • Cornea (clear membrane- bends light inward) to
    focus images
  • On a light sensitive layer
  • Back of closed space layer of photo-receptors
  • In Retina (thick as postage stamp)
  • Muscles alter shape of lens focus
  • Accommodation is another name for changing
  • gt-(?----)
  • gt-(-gt-)

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Structure of the Eye
  • Iris controls amount of light entering eye
  • Colored
  • Muscle that expands and contracts
  • Changes size of pupil
  • Dilation enlarge
  • Constriction narrow

Virtuous Humor- Jelly like substance fills the
  • Depends on Wavelength the Visible spectrum
    (Electromagnetic energy the eyes respond to)

  • Wavelength ?
  • Visible light starts _at_ 400 nanometers
  • one billionth of a meter
  • purple or violet
  • Long light waves blue, green, yellow, orange,
    and red maximum 700 Nanometers
  • Hue basic color categories- Red, orange, yellow,
    green, blue, Indigo, violet -gt correspond to
    lights wave lengths
  • Saturation pure color narrow band of light
  • Brightness- amplitude, height of light waves-
  • More energy more color, brighter more intense.

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The Retina
  • Retina is located at the back of the eye
  • Light is focused on to the retina----then
    sensation- is received by receptors in the
    retina--?to the optic nerve.
  • Photo-receptor cells Rods and Cones
  • Fovea- cup shape, on retina, only has cones,
    greatest visual Acuity- or sharpness
  • Blind Spot- where optic nerve leave the eye-

Rods and Cones
  • 100 million in each eye
  • Can not detect color
  • Black and white pure rod vision
  • More sensitive to light
  • Allow sight in dim-light
  • Sensitive to movement
  • Peripheral vision
  • 6.5 million in each eye
  • Work best in bright light
  • Color sensation
  • Fine detail
  • Mostly center of eye
  • Fovea contains only cones
  • Most sensitive to yellow 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 Vision
  • Side vision- area outside Fovea
  • Rod vision- not very sharp-

LASIK- Lasor Assisted Insitu keratomileusis Reshap
es and stretches the cornea Increases degree of
cornea bending light
Vision Problems
  • Hyperopia Difficulty focusing nearby objects
    (farsightedness) eye is too short-
  • Myopia Difficulty focusing distant objects
  • Astigmatism Cornea, or lens defect that causes
    some areas of vision to be out of focus
    relatively common-lens not symmetrical
  • Lenses correct vision by changing the path of

  • Visual Acuity Sharpness
  • Normal 20/20
  • 20 distance you can see what average people see
    at 20 ft.
  • 20/40 you can only see at 20 feet what most
    people see at 40 feet
  • 20/200 correct legal blindness

Color Theories- what happens in the eye?
  • Trichromatic- three types of vision receptors
    (cones) each sensitive to Red, Green, and Blue
  • 3 visual pigments
  • Fire nerve impulses _at_ different rates to produce
    color sensations
  • Opponent Process Theory (3 sets of color
  • Vision analyzes color in either or messages
  • Red or green
  • Yellow or blue
  • Black or white
  • After Image- OPT

After Images
  • Visual sensations that persist after stimulus is
    removed seeing spots
  • Relates to Opponent Process Theory-
  • Fatigue caused by one response causes after image
    of opposite color system
  • Both theories apply
  • Tri-color
  • 3 visuals Pigments light sensitive chemicals
  • Red, Green, or Blue
  • 3 types of cones- Fire nerve impulse_at_ different
    rates to produce color sensations

Mechanical View of Color Sensation
  • Colors are influenced in the brain by other
    colors nearby
  • Simultaneous color contrast
  • Affect perception of color (p 186)

Ishihara Test
  • Cannot perceive colors
  • Lacks cone or cones dont function
  • Rare
  • Genetic- Affecting Red and Green Blue pigments
    in Cones
  • Color weakness people cant see certain colors
  • 8 of males, 1 of women- see red-green as yellow
    and brown

Dark Adaptation
  • Increased retinal sensitivity to light after
    entering the dark
  • similar to going from daylight into a dark movie
  • Rhodopsin Light-sensitive pigment in the rods
    involved with night vision
  • Night Blindness Blindness under low-light
    conditions hazardous for driving at night

  • Dot of light
  • More pixels sharper image

  • Uses Data Reduction
  • (Select, Analyze, Filter info)
  • Stimulus for hearing Waves
  • Vibrating objects sound waves (rhythmic
    movement of air molecules)
  • Peaks compression
  • Valleys rarefaction
  • Frequency of sound waves waves per/sec
    (Corresponds to)
  • Pitch tone of the a sound

  • Amplitude height of sound wave
  • Tells how much energy it contains
  • Relates to loudness (sound intensity)

Anatomy of Audition
Sound waves are converted to nerve impulses
through the Auditory System
  • Pinna
  • Tympanic membrane
  • Auditory Ossicles
  • Malleus
  • Incus
  • Stapes
  • Cochlea
  • Corti
  • Steriocilla
  • Auditory nerve fiber

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Audition Theories
  • Frequency Theory
  • As pitch increases-nerve impulses of same
    frequency are fed to auditory nerve
  • Example-gt 800 hertz tone of vibrations per
    second 800 nerve impulses per second
  • Place Theory
  • Higher and lower tones excite specific areas of
    the cochlea
  • Hair cells respond to area greatest movement

2 Types of Deafness
  • Conduction Deafness
  • Transfer vibration to inner ear is weak
  • Ear Drum or Ossicles are damaged
  • Hearing Aid makes sounds clearer and louder
  • Nerve Deafness- damage to hair cells or auditory
  • Stimulation Deafness
  • Loud sounds damage hair cells in Cochlea
  • 85 decibels may cause permanent loss
  • Temporary Threshold shift
  • Partial/transitory hearing loss _at_ 120 decibels

  • Tinnitus- ringing- buzzing sensation

Vestibular System
Fluid filled sacs- sensate movement,
acceleration, gravity
  • Inner Ear
  • Associated with motion sickness
  • Sense organs for balance (Fluid in the inner of
    the ear)

Motion Sickness and Vestibular System
  • Sensory Conflict Theory
  • When sensations from vestibular system dont
    match sensations from eyes and body conflict
  • Causes motion sickness
  • Why?
  • Evolution- poisons attack vestibular system-?body
    reacts with nausea

  • Again- uses
  • Is a chemical sense (receptors that respond to
    chemical molecules)
  • Data Reduction Transduction-
  • Airborne Molecules contact receptor cells in
  • 5 million nerve fibers in nasal passages

Axons go directly to olfactory bulbs in brain To
olfactory cortex limbic system.
  • Defective sense of smell for single odor
  • Suggests these are specific receptors for
    specific odors
  • 1 person in a hundred cant smell

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Smell Receptors
  • Shape of receptors impacts smells
  • Lock and key theory- some odors have specific
    shapes that fit receptors
  • of activated receptors tells how strong an odor
  • Scent likes and dislikes are learned

  • Animals- secrete-
  • Affect mating
  • Sexual behavior
  • Associated with recognition of family member
  • Territorial marking
  • Vomeronasal organ (VNO) sense organ for
  • Receptors in septum
  • Produces vague feelings
  • Affects general mood
  • Well being
  • Attraction
  • Unease and anxiety
  • May cause womens menstrual cycles to synchronize

  • Sense of Taste
  • Chemical Sense
  • Tongue includes
  • papillae- taste buds and receptors
  • Associated with medulla oblongata
  • Taste sensitivity of taste buds on tongue
  • Taste preferences are acquired
  • Four basic tastes
  • Sweet
  • Bitter
  • Salt
  • Sour
  • Flavor

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Somoesthetic Sense (Touch)
  • The Skin- cutaneous
  • Kinesthetic/Tactile Receptors (movement) in
    muscles and in joints
  • Detect body position and movement
  • Collects info- pressure, pain and temperature
  • Neurons to spinal cord-gt medulla-gt
    thalamus-gtsomatosensory cortex

Where is our body most sensitive? Density of
  • Based on density of receptors-
  • There is an increase in density of receptors in
  • Lips
  • Tongue
  • Face
  • Hands
  • Genitals
  • Receptors
  • 200,000 nerve endings for temperature
  • 500,000 touch and pressure
  • 3 million for pain

Pain Receptors
  • Varied distribution through the body
  • 232 pain points per square centimeter behind the
  • 184 in buttocks
  • 60 on the thumb
  • 44 on nose

Nerve Fibers Large Small
  • A-delta fibers (mylinated) carry sharp
  • Pricking pain sensations
  • Skin
  • Muscles
  • Joints
  • Tendons
  • Sharp bright fast
  • From specific body parts
  • Warning system
  • Slower nagging, aching widespread
  • C-fibers (un-mylinated) carry long lasting dull
    aches and burning sensations
  • Reminding system
  • Reminds brain body has 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 bodys surface.
Sensory Gating
  • Sensory Gating Facilitating or blocking sensory
    messages in spinal cord

Gate Control Theory of Pain
  • Gate Control Theory Pain messages from different
    nerve fibers pass through the same neural gate
    in the spinal cord.
  • If gate is closed by one pain message, other
    messages may not be able to pass through
  • Gate may close other message cant pass
  • Fast pain (Large Nerves)
  • may close gate of slower (deeper Small Nerve)
    pain message Example Electric shock as pain
  • Acupuncture Closes gates
  • Beta Endorphins-In Pituitary Gland
  • Kill pain
  • Chemical similar to Morphine

Controlling Pain
  • Fear, or high levels of anxiety, almost always
    increase pain
  • If you can regulate a painful stimulus, you have
    control over it
  • Distraction can also significantly reduce pain
  • The interpretation you give a stimulus also
    affects pain

Anxiety Control Attention Interpretation
Coping With Pain
  • Prepared Childbirth Training Promotes birth with
    a minimal amount of drugs or painkillers
  • Counter-irritation Using mild pain to block more
    intense or long-lasting pain (gate theory)

Phantom Limb Pain
  • Video short
  • Video

Sensory Adaptation
  • Getting used to it.
  • unchanging stimuli- causes fewer impulses to
    the brain.
  • Changing stimulation causes more impulses
  • Selective Attention
  • Tune in on single sensory message while excluding

Synesthetic Synesthesia
  • Someone who feels sensations
  • With multiple senses
  • Example hearing colors
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