CHAPTER 3 (Sensation and Perception)

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CHAPTER 3 (Sensation and Perception)

• Michael L. Farris
• Psychology 101

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Subliminal Persuasion

• Famous Attempt at Subliminal Advertising
• New Jersey theater
• Eat Popcorn Drink Coca-Cola
• Words appeared for 1/3000 of a second every 5
  seconds
• At that speed, they were below the normal
  threshold for awareness.
• During the 6 weeks the messages ran, the firm
  claimed increases in popcorn and Coca-Cola sales.
• What do you think? Did the sales increase
  because of the subliminal messages, or something
  else?
• Please see pages 108, 117 118 in your text for
  more information.

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Backmasking

• In another uproar over subliminal perception,
  critics charged that spoken messages recorded
  backward (called backmasking) in rock music are
  perceived unconsciously by listeners.
• Queen (Another One Bites the Dust)
• The Beatles (White Album)
• Experiment Vokey and Read recorded a variety of
  sentences
• backward, including selections from Lewis
  Carrols
• Jabberwocky and the 23rd Psalm from the Bible.
• Their tests clearly showed that the backward
  sentences were
• not recognized.
• Still, shopping malls sometimes use subliminal
  messages
• embedded in the music (Dont Steal, Buy More,
  Orange
• Julius Rules)
• Conclusion There is little evidence that
  subliminal messages greatly
• influence behavior. P.118.

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Sensitivity

• Sensation The incoming flow of information from
  the environment. P.84.
• Perception The process by which the brain
  organizes sensations into meaningful patterns or
  representations of the world. (p.106)
• Hearing is much more sensitive than taste
• A voice or musical instrument that is off pitch
  1/3 of 1 will be noticeable.
• For taste, a 20 change is necessary to produce a
  JUST NOTICEABLE DIFFERENCE (p.84).
• If a cup of coffee has 5 teaspoons of sugar in
  it, 1 more (1/5 of 5) must be added before you
  would notice an increase in sweetness.
• Just Noticeable Difference Any noticeable
  difference in a stimulus.
• Absolute Threshold The minimum amount of
  physical energy necessary to produce a sensation.

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Absolute Thresholds

• Sensory Modality Absolute Threshold
• Vision Candle flame seen at 30 miles on a
  clear, dark night
• Hearing Tick of watch
  under quiet conditions at 20 feet
• Taste 1 teaspoon of sugar in 2 gallons of
  water
• Smell 1 drop of perfume diffused into a
  three-room apartment
• Touch A bees wing falling
  on your cheek from 1 cm above
• Please see pages 84-85 in your text for more
  information.

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Vision The Human Eye
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Vision Problems (P.87-93)

• The shape of the eye affects focusing.
• Hyperopia (farsightedness) If the eye is too
  short, nearby objects cannot be focused, but
  distant objects are clear.
• Myopia (nearsightedness) If the eyeball is too
  long, the image falls short of the retina, and
  distant objects cannot be focused.
• Astigmatism When the cornea or the lens is
  misshapen, part of the visual field will be
  focused, and part will be fuzzy. In this case,
  the eye has more than one focal point.
• All three visual defects can be corrected
  by placing glasses or contact lenses in front of
  the eye. These added lenses change the path of
  incoming light to restore crisp focusing.
• As people age, the lens becomes less
  flexible and less able to accommodate. Since the
  les must do its greatest bending to focus nearby
  objects, the result is presbyopia, or
  farsightedness due to aging.
• Perhaps you have seen a grandparent
  reading a newspaper at arms length because of
  presbyopia. If you now wear glasses for
  farsightedness (myopia), you may need bifocals as
  you age.
• (Unless your arms grow longer in the meantime.)

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Accommodation

• Accommodation (p.88) The process of adjusting
  the configuration of the lenses to bring images
  into focus on the retina.
• Try the cocktail sausage demonstration. Hold
  both index (pointer) fingers at arms length,
  pointing at each other.
• Leave a 6 inch gap, and focus on the wall through
  the gap. Slowly bring the fingers together,
  staring at the wall through the gap.
• Stop just before your fingers touch. See the
  sausage? Yum!

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Rods and Cones

• Rods Rod-shaped receptors in the retina which
  predominate in low (dim) light conditions.
  Species active only at night tend to have
  rod-only retinas. Peripheral vision is mainly rod
  vision, and occurs at the edges of the visual
  field. At night, the most visible color to our
  rods is blue or blue-green. Thats why police
  use blue lights!
• Cones Receptors in the retina that predominate
  in good (bright) lighting, and provide
  high-acuity (finely detailed) colored perceptions
  of the world. In dim illumination, there is not
  enough light to reliably excite the cones, and
  the more sensitive rod-mediated vision
  predominates. The most visible color to cones is
  yellowish green. Thats why some fire trucks and
  roadside work crew vests are this color!
• An area at the center of the retina containing
  only cones is called the Fovea.
• Please see pages 88-89 in our text for more
  information.

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Color Blindness

• A person who is color blind cannot perceive
  colors (the world looks like a black and white
  movie). How do we know?
• In a few rare cases, people have been color blind
  in only one eye and can compare.
• Two colors of equal brightness look exactly alike
  to the color blind individual.
• The color blind person either lacks cones or has
  cones that do not function normally.
• Color blindness is caused by changes in the genes
  that control red, green, and blue pigments in the
  cones.
• Please see pages 92-93 in our text for more
  information.

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Are you colorblind? Which numbers do you see?
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Colorblind Test

• If picture A looks like number 3, and picture B
  looks like number 73, you're ok. If picture A
  looks like number 5 and picture B looks like
  nothing at all, you may have a deficiency in your
  color vision !
• Red-green color blindness is a recessive,
  sex-linked trait. That means it is carried on
  the X, or female, chromosome. Women have two X
  chromosomes, so if they receive only one
  defective color gene, they still have normal
  color vision.
• Color blind men, however, have only one X
  chromosome, so they can inherit the defect from
  their mothers (who are usually not color blind
  themselves).
• The red-green color blind person sees both reds
  and greens as the same color, usually as a
  yellowish brown.

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Dark Adaptation

• Dark Adaptation (Coon, p.170) is the
  dramatic increase in retinal sensitivity to light
  that occurs in darkness.
• If you enter a dark movie theatre on a sunny
  day, you practically need to be led to your seat.
  After a short time, however, you begin to see
  the entire room in detail.
• Studies show that it takes about 30-35
  minutes of complete darkness to reach maximum
  visual sensitivity. A completely dark-adapted
  eye is 100,000 times more sensitive to light. At
  that point, the human eye is almost as light
  sensitive as the eyes of an owl!

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Blind Spot

• Blind Spot (pgs.89-90) The gap in the receptor
  layer of the retina where the bundle of retinal
  ganglion cell axons leave the eye. There are no
  rods or cones where the optic nerve leaves the
  eye.
• One of the most dramatic experiments to perform
  is the demonstration of the blind spot. The blind
  spot is the area on the retina without receptors
  that respond to light. Therefore an image that
  falls on this region will NOT be seen. It is in
  this region that the optic nerve exits the eye on
  its way to the brain. To find your blind spot,
  look at the image below or draw it on a piece of
  paper

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Blind Spot Demonstration

• To draw the blind spot tester on a piece of
  paper, make a small dot on the left side
  separated by about 6-8 inches from a small on
  the right side.
• Close your right eye. Hold the image (or place
  your head from the computer monitor) about 20
  inches away.
• With your left eye, look at the . Slowly bring
  the image (or move your head) closer while
  looking at the .
• At a certain distance, the dot will disappear
  from sight...this is when the dot falls on the
  blind spot of your retina.
• Reverse the process. Close your left eye and look
  at the dot with your right eye. Move the image
  slowly closer to you and the should disappear!

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Find Your Blind Spot!
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Complementary Colors

• Complementary colors Pairs of colors that
  produce white or gray when combined in equal
  measure (for example, red light and green light).
  
• This is based on the opponent-process theory
  (Ewald Hering, 1878), which observes that
  complementary colors cannot exist together (there
  is no such thing as bluish yellow or reddish
  green).
• Another observation is that the afterimage
  produced by staring at yellow is blue and vice
  versa. Blue is the complementary color to
  yellow. Red is complementary to green.
• (For more information, please see page 58 in the
  Pinel text.)
• A Demonstration follows with the next slide
  Stare at the
• center of the red box for 30 seconds (or a slow
  count of 30).
• Then look at the next (blank) slide, or a white
  surface.
• What do you see?

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Hearing

• Any vibrating object (a tuning fork, the string
  of a musical instrument, or the vocal cords) will
  produce sound waves (cyclic, wave-like movement
  of air molecules).
• Other materials, such as fluids or solids, can
  also carry sound. But sound does NOT travel in a
  vacuum (p.94). Movies that show characters
  reacting to the roar of alien starships or
  titanic battles in deep space are in error.

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How We Hear

• The pinna (visible outer ear) funnels sound to
  the tympanic membrane (ear drum), which vibrates
  and moves three small bones (auditory ossicles).
  These bones link the eardrum with the cochlea.
• The cochlea (p.95), a snail shaped organ that
  makes up the inner ear, is the organ of hearing.
  
• There is fluid in the cochlea, and waves in the
  fluid are detected by tiny hair cells, which
  generate nerve impulses to be sent to the brain.
  The bristles on hair cells, called cilia, are
  sensitive to movement.

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Deafness

• Conduction Deafness (p.97) Occurs when there is
  poor transfer from the eardrum to the inner ear.
  The eardrum or ossicles may be damaged or
  immobilized by disease or injury. Often, a
  hearing aid will overcome conduction deafness.
• Nerve Deafness (p.97) Results from damage to the
  hair cells or auditory nerve. Hearing aids dont
  help, because auditory messages are blocked from
  reaching the brain. However, a new type of
  artificial hearing system is being developed that
  may help.
• Stimulation Deafness (p.97) Occurs when very
  loud sounds damage hair cells in the cochlea.
  Each of us starts life with about 32,000 hair
  cells. However, we begin losing them the moment
  were born. By age 65 more than 40 are gone.
• If you work in a noisy environment or enjoy loud
  music, motorcycling, or similar pursuits, you
  (we!) may be risking stimulation deafness.
• Hair cells (which are about as thick as a cobweb)
  are very fragile and easily damaged.
• Once dead, they are never replaced. When you
  abuse them, you lose them.

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Hearing Loss

• The danger of hearing loss depends on both the
  loudness of sound and how long you are exposed to
  it.
• Daily exposure to 85 decibels or more may cause
  permanent hearing loss.
• Even short periods at 120 decibels (a rock
  concert) may cause a temporary threshold shift (a
  partial, transitory loss of hearing).
• Brief exposure to 150 decibels (a jet airplane
  nearby) can cause permanent deafness.
• Please see page 97 for more information on
  Hearing Loss.

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Decibel Levels of Common Sounds

• screaming child90 dB
• subway train100 dB
• diesel truck100 dB
• jackhammer100 dB
• helicopter105 dB
• power mower105 dB
• shouting in ear110 dB
• live rock music90-130 dB
• football stadium117 dB
• band concert120 dB
• thunder120 dB
• car horn120 dB
• jackhammer130 dB
• air raid siren130 dB
• noisy squeeze toys135 dB
• PAIN STARTS 140 dB
• gunshot140 dB
• jet engine140 dB
• rocket launching180 dB

• softest audible sound 0 dB
• normal breathing 10 dB
• rustling leaves20 dB
• whispering25 dB
• clothes dryer60 dB
• normal conversation60 dB
• dishwasher65 dB
• car70 dB
• busy traffic75 dB
• alarm clock80 dB
• noisy restaurant80 dB
• average factory85 dB

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Tinnitus

• Tinnitus is a ringing or buzzing sensation
  following exposure to loud sounds (Coon,p.176).
• If you feel or hear this ringing or buzzing,
  chances are good that hair cells have been
  damaged.
• Almost everyone has tinnitus at times, especially
  with increasing age. But after repeated sounds
  that produce this warning, you can expect to
  become permanently hard of hearing.
• A study of people who regularly went to amplified
  concerts found that 44 had tinnitus and most had
  some hearing loss (Meyer-Bisch, 1996).
• The next time you are exposed to a very loud
  sound, remember to take precautions against
  damage. (Earplugs are good, and fingers are
  always handy in an emergency!)

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Smell and Taste (p.99)

• Olfaction The sense of smell.
• Gustation The sense of taste.
• 1 person out of 100 cannot smell anything at all!
  (Total anosmia)
• Smell may seem like a minor sense that we can
  live without. Why is this anosmia dangerous?
• Smell and taste are very closely linked. One
  affects the other.
• Sensory Adaptation Decreases our response to a
  constant or unchanging stimulus (p. 86). This is
  why we cant smell something as well after a few
  minutes of being in a room with it.
• Taste buds (the receptor organs for taste) are
  located mainly on the top side of the tongue, but
  a few are found elsewhere inside the mouth.
• There are 4 basic taste sensations
• Sweet (least sensitive)
• Salt (a bit sensitive)
• Sour (sensitive)
• Bitter (most sensitive)
• Why might bitter and sour foods be most
  detectable?

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The Somesthetic Senses

• A gymnast flying through a routine on the
  uneven bars may rely as much on the somesthetic
  senses as on vision (soma means body, esthetic
  means feel).
• Somesthetic senses include
• Skin senses (touch)
• Kinesthetic senses (receptors in the muscles and
  joints that detect body position and movement)
• Vestibular senses (receptors in the inner ear for
  balance, gravity and acceleration).
• Motion Sickness Youve probably seen astronauts
  on television, playfully enjoying weightlessness.
  In reality, if you were to ride into space, it
  is about 70 likely that you would throw up!
  (p.104)
• Space sickness is similar to sea-sickness,
  air-sickness, and car-sickness. It is especially
  intense because weightlessness drastically alters
  sensations the brain receives from the head,
  muscles, and joints.

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Motion Sickness

• Motion sickness is related to the vestibular
  system (p.104).
• Fluid filled sacs in the vestibular system
  (called otolith organs) are sensitive to
  movement, acceleration and gravity.
• The otolith organs contain tiny crystals in a
  soft, gelatin-like mass. The tug of gravity or
  rapid head movements can cause the mass to shift.
  This stimulates hair-like receptor cells,
  allowing us to sense gravity and movement through
  space.
• The best explanation of motion sickness is the
  sensory conflict theory (Coon, p.181) According
  to this theory, dizziness and nausea occur when
  sensation from the vestibular system fail to
  match information received from the eyes and
  body. On solid ground, the information from the
  vestibular system, vision, and kinesthesis
  usually matches. However, in a heaving, pitching
  boat, car, or airplane, a serious mismatch can
  occur-causing heaving of another kind.

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Selective Attention

• Selective Attention (p.106) Voluntarily focusing
  on a specific sensory input.
• Seat of the Pants Phenomenon As you sit in
  class, receptors for touch and pressure in the
  seat of your pants are sending nerve impulses to
  your brain. Although these sensations have been
  present all along, you were probably not aware of
  them until just now. The seat of the pants
  phenomenon is an example of selective attention.
• The cocktail party effect Another example of
  selective attention. We are able to tune in on a
  single sensory message (conversation) while
  excluding others. If you are listening to one
  person intently, another person nearby can talk
  backward and you will not notice the strange
  speech! (Wood Cowan, 1995)

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Sensory Gating of Pain

• One type of pain will sometimes cancel another
  (p.103)
• Gate Control Theory suggests that pain messages
  from different nerve fibers pass through the same
  neural gate in the spinal cord.
• If the gate is closed by one pain message,
  other messages may not be able to pass through.
• Messages carried by large, fast nerve fibers seem
  to close the spinal pain gate directly. Doing so
  can prevent slower, reminding system pain from
  reaching the brain.
• Pain clinics use this effect by applying a mild
  electrical current to the skin. Such
  stimulation, felt only as a mild tingling, can
  greatly reduce more agonizing pain.
• Counterirritation (Coon, p.188) Using mild pain
  to block more intense or long lasting pain. This
  explains why some of the oldest pain control
  techniques work (applying ice packs, hot-water
  bottles, mustard packs, vibration, or massage to
  other parts of the body). Pinching yourself or
  digging nails into the flesh may help at the
  dentist. Focus attention on the pain you are
  creating, and increase its intensity anytime the
  dentists work becomes more painful. It works
  for many people, but not all.

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Acupuncture

• Some researchers believe that gate control theory
  explains the painkilling effects of acupuncture
  (the Chinese medical art of relieving pain and
  illness by inserting thin needles into the body).
  P.103.
• Acupuncture has an interesting side effect not
  predicted by sensory gating. People given
  acupuncture often report feelings of
  light-headedness, relaxation, or euphoria. Why?
• To combat pain, the brain causes the pituitary
  gland to release painkilling chemicals called
  endorphins. (Endo means within, orphin means
  opiate). P.103.
• Chemically, endorphins are quite similar to
  morphine.

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Pain Beta-Endorphins

• The painkilling effect of placebos (fake pills or
  injections) appears to be based on a rise in
  endorphin levels (p.26).
• A release of endorphins also seems to underlie
  runners high, masochism, acupuncture, and the
  euphoria sometimes associated with childbirth and
  painful initiation rites.
• In each case, pain and stress cause the release
  of endorphins. These in turn induce feelings of
  pleasure or euphoria similar to morphine
  intoxication.
• The high often felt by long-distance runners
  serves as a good example of the endorphin effect.
  In one experiment, runners were tested for pain
  tolerance. After running 1 mile, each was tested
  again. In the second test, all could withstand
  pain about 70 longer than before. The runners
  were then given naloxone, a drug that blocks the
  effects of endorphins. Following another 1 mile
  run, the subjects were re-tested. This time they
  had lost their earlier protection from pain.
• People who say they are addicted to running may
  be closer to the truth than they realize.