General Psychology Chapter 3: Sensation and Perception

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General PsychologyChapter 3 Sensation and
Perception
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• Sensation
• senses pick up sensory stimuli and send it to the
  brain
• Perception
• brain organizes and interprets sensory information

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Sensation

• Absolute Threshold
• minimum amount of sensory stimulation that can be
  detected 50 of the time
• Difference Threshold
• smallest increase or decrease in a stimulus
  required to produce the JND
• Just Noticeable Difference (JND)
• the smallest change in sensation a person is able
  to detect 50 of the time

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1 cm
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• Sensory Adaptation
• adapt to unchanging stimulus so less sensitive to
  it
• allows you to shift your attention to what is
  most important at any given time

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Vision

• Lens
• behind iris changes shape as it focuses images
  on the retina (accommodation)
• Retina
• contains the rods and cones at the back of the
  eye
• rods allow see black, white and gray in dim light
• cones allow see color and details in adequate
  light

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Theories of Vision

• Trichromatic theory
• 3 types of cones which are most sensitive to red,
  green or blue which combine to produce all colors
• research supports the retina has 3 types of cones
• Opponent-process theory
• 3 classes of cells increase their firing rate to
  signal one color and decrease their firing rate
  to signal the opposing color (red/green,
  yellow/blue, white/black)
• supported by afterimage

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Theories of Hearing/Audition

• Place Theory
• sounds of different frequency or pitch cause
  activation at certain locations along the
  receptor cells of the cochlea
• Frequency Theory
• receptor cells vibrate the same number of times
  as the sounds that reach them

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Smell and Taste

• Olfactionthe sensation of smell
• Pheromoneschemicals excreted by humans and
  animals that act as signals to, and elicit
  certain patterns of, behavior from members of the
  same species
• animals mark off territories from same sex and
  signal sexual receptivity in opposite sex
• humans unconsciously respond to pheromones for
  mating and to their relations

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• Gustationsensation of taste
• 5 basic tastes
• sweet
• sour
• salty
• bitter
• umami (triggered by glutamate)

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• 3 groups of taste sensitivity
• Nontasters are unable to taste some sweet and
  bitter compounds, but do taste most other
  substances
• Medium tasters have an average sense of taste to
  sweet and bitter compounds
• Supertasters taste certain sweet and bitter
  compounds with far stronger intensity than other
  people

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Skin Senses

• Tactilepertaining to the sense of touch
• Painmotivates us to tend to injuries, restrict
  activity, and seek medical help and to avoid
  pain-producing circumstances

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Spatial Orientation Senses

• Kinesthetic sense
• gives information about movement of body and its
  parts
• Vestibular sense
• provides information about the bodys orientation
  in space

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Perception

• Gestalt principles of perceptual organization
• Figure-groundas you view your world, some
  objects seem to stand out from the background
• Similarityobjects that have similar
  characteristics are perceived as a unit
• Proximityobjects that are close together in
  space or time are usually perceived as
• belonging together
• Continuitytend to perceive figures or objects as
  belonging together if they appear to form a
  continuous pattern
• Closureperceive figures with gaps as complete

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• Depth perception
• The ability to see in three dimensions and to
  estimate distance

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• Binocular depth cues
• Depth cues that depend on two eyes working
  together
• Convergence
• Occurs when the eyes turn inward to focus on
  nearby objects the closer the object, the
  greater the convergence
• Binocular disparity (or retinal disparity)
• Difference between the two retinal images formed
  by the eyes slightly different views of the
  objects focused on

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• Monocular depth cues
• Interposition
• Linear perspective
• Relative size
• Texture gradient
• Atmospheric perspective
• Motion parallax

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• Apparent motionpsychological construct movement
• Phi Phenomenon
• UFOseyes move but see as object moving

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• Ambiguous Figures
• Can be seen in different ways to make different
  images

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What do you see?
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• Impossible figures
• Do not seem unusual at first
• Figures that cannot be built

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• Illusion
• A false perception of actual stimuli involving a
  misperception of size, shape, or the relationship
  of one element to another

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Influences on Perception

• Bottom-up processing
• Information processing in which individual
  components or bits of data are combined until a
  complete perception is formed
• Top-down processing
• Application of previous experience and conceptual
  knowledge to recognize the whole of a perception
  and thus easily identify the simpler elements of
  that whole

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• Bottom up
• 1 3 5 7 9 ? 13 ? ?

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• Can you raed tihs? I Cdnuolt blveiee taht I
  cluod aulaclty uesdnatnrd waht I was rdanieg.
  The phaonmneal pweor of the hmuan
  mnid--aoccdrnig to rscheearch at Cmabrigde
  Uinervtisy, it deosn't mttaer in waht oredr the
  ltteers in a wrod are, the olny iprmoatnt tihng
  is taht the frist and lsat ltteer be in the rghit
  pclae.
• The rset can be a taotl mses and you can sitll
  raed it wouthit a porbelm. Tihs is bcuseae the
  huamn mnid deos not raed ervey lteter by istlef,
  but the wrod as a wlohe. Amzanig huh? yaeh and I
  awlyas tghuhot slpeling was ipmorantt!

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• Perceptual set
• An expectation of what will be perceived, which
  can affect what actually is perceived
• Psychologists in a mental hospital as
  schizophrenics

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• Inattentional blindness
• The phenomenon in which we miss an object in our
  field of vision because we are attending to
  another
• Gorilla video tape
• Studies showed that drivers often failed to
  perceive vehicles braking directly in front of
  them while engaged in hands-free cell phone
  conversations