Sensation and Perception - PowerPoint by HC120614044549

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									Sensation and Perception
       Absolute Threshold

There are
things that we
cannot sense.
     Differences are Different
• Difference threshold:
  – minimum difference between two stimuli that
    one can detect 50% of the time
  – increases with magnitude of stimulus
• weight        2%
• Taste         20%
• Sound         .3%
              Adaptation
•   Mom’s apple pie
•   Your perfume or cologne
•   Feeling your underwear carving deep
    groves in your body
•   Your breath
•   The image of your sweetheart

       All senses adapt, even vision
                 Vision
• Psychologists have studied vision more
  than any other sense
         The Visual System
• Light enters the
  eye through the
  cornea

• Neural impulses
  are created in
  the retina by
  receptor cells
  – rods and cones
The retina
                 Rods and Cones
• Rods and cones are named
  for their shapes.

• Rods
   – highly light sensitive, responsible for
     night vision, and responsible for
     brightness perception

• Cones
   – less light sensitive, most useful in
     daylight, and responsible for color
     vision
        Trichromatic Theory
• There are three types of cones:
  – red, green, and blue
         Opponent-Process Theory
•     Color-sensitive ganglion cells are arranged in opposing cells
    –    Red-green, yellow-blue, black-white

•    Activation of one cone inhibits another

•    May explain some kinds of afterimages

    1.   Continual viewing of red weakens the ability to inhibit green
    2.   Remove red and you see green
                  Sound
• The physical stimuli for the sense of
  hearing are sound waves
  – Compressions and expansions of air
    molecules
The Ear
Hearing Loss
Hair Cells
Smell
Olfactory Bulb
                   Taste
• Receptor cells are in buds on tip, sides,
  and back of the tongue.
Taste Bud
• Salty and sour detection is needed to control salt
  and acid balance
• Bitter detection warns of foods containing
  poisons—many of the poisonous compounds
  produced by plants for defense are bitter.
• The quality sweet provides a guide to calorie-
  rich foods.
• Umami (the taste of the amino acid glutamate)
  may flag up protein-rich foods.
          The Skin Senses
• Receptors in the skin
  – Touch, Temperature, Pain   “Paradoxical Heat”
                                                    chapter 3




Kinesthetic & Vestibular Senses
 Kinesthetic sense
  Muscle movement, changes in posture, and strain
    on muscles and joints

 Vestibular sense
  Equilibrium & body position in space
chapter 3
                                   chapter 3



How Is Perception Different From
Sensation?
 Sensation
  raw sensory data that the
    brain receives from the
    senses

 Perception
  process of organizing,
    interpreting, and giving
    meaning to that raw data
                       chapter 3




Perceiving a Pattern
                                             chapter 3




Figure-Ground Distinction
 Figure
  Entity perceived to stand apart from the
   background

 Ground
 Background against which a figure appears
                                 chapter 3




Random dots or something more?
GroupingofPrinciples
Gestalt Principles Perceptual Organization
                                               chapter 3




Perceptual Constancy
 Our tendency to perceive objects as unchanging,
 even given changes in sensory stimulation

 Kinds of constancies
  size constancy

 shape constancy

 brightness constancy

 color constancy
                                           chapter 3




Shape Constancy
 Tendency to see an object as the same
 shape no matter what angle it is viewed
 from
                                           chapter 3




Size Constancy
 The perception of object’s size doesn’t
 change, regardless of the change in
 distance from eye and size of image on
 retina.
  How do we know how far away
          something is
• Monocular cues: Depth cues requiring only
  one eye

• Binocular cues: Depth cues requiring both
  eyes
                            chapter 3




Monocular Cues
 Kinds of monocular cues:
 Interposition
 Linear perspective
 Aerial perspective
 Elevation
 Texture gradient
 Shadowing
 Motion parallax
                         chapter 3




Perspective-based Cues
 Linear perspective
 Aerial perspective
 Elevation
                                                   chapter 3




Other monocular cues
 Texture Gradient
  Objects seen at greater distances appear to be
   smoother and less textured.

 Shadows

 Motion parallax
                                            chapter 3




Binocular Cues
 Cues that rely on two visual fields that
 partially overlap:

 Retinal disparity
 Convergence
                           chapter 3




Sound Localization
 Monaural cues
 Cues to sound
   location that require
   only one ear

 Binaural cues
  Cues to sound
    location requiring
    both ears to work
    together
                   chapter 3




Visual Illusions
            chapter 3




Fig. 3-38
Julian Beever
   Everything is fake,
even the hose and water
       Observer Characteristics
•   Motivation
•   Values
•   Expectations - Perceptual Set
•   Context
•   Experience and culture
•   Personality

								
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