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					             Perception




The process of organizing and interpreting
  information, enabling us to recognize
     meaningful objects and events.
Auditory Illusions




         If the sounds do not work click here for link.
        Absolute Threshold
• The smallest amount
  of a stimuli we can
  detect about half of
  the time.
               Subliminal Messages
                             Do you hear
                             "Now he

                                             • Stimuli below our
                             uses
                             marijuana.“?
                                               absolute threshold.
                                             • Backmasking
                                             • 25th frame
                                             • Do Subliminal
                                               Messages work?
                                             • Probably a placebo
Do you hear        Do you hear Pass the        effect
               Do you hear"Play backwards. Hear
                   gun now. It kills the
“Ah, see me.
               words sung.“?
                   love, the love is cold”?
I'm not too
young”?
            (Just Notable Difference)
              Difference Threshold
The smallest amount of change needed to detect in a stimulus before we detect a
change.
                 Weber’s Law
• Computes the Just
  Noticeable Difference.
• The change needed is
  proportional to the
  original intensity of the
  stimulus.
• The more intense the
  stimulus the more
  change is needed to
  notice the difference.
• 8% for vision.
Perceptual Ideas
           Signal Detection theory
• Absolute thresholds
  are not really
  absolute.
• Things like motivation
  or physical state can
  effect what we
  sense.
• False Positives
• False Negatives
My wife could sleep through a war, but if
one of our sons even whimpers, she is up!!!
Top-Down Processing
          • We perceive by filling
            the gaps in what we
            sense.
          • I _ant ch_co_ate ic_
            cr_am.
          • Based on our
            experiences and
            schemas.
          • If you see many old men
            in glasses, you are more
            apt to process a picture
            of an old man (even when
            you may be in error).
      Bottom-Up Processing
• Also called feature
  analysis.
• We use the features
  on the object itself
  to build a
  perception.
• Takes longer that      Click to see an example
                         of bottom –up
  top-down but is more   processing.
  accurate.
Figure Ground Relationship

           Our first perceptual
           decision is what is the
           image is the figure and
           what is the background.
                Gestalt Psychology
• Gestalt psychologists focused on
  how we GROUP objects together.
• We innately look at things in groups
  and not as isolated elements.
• Proximity (group objects that are
  close together as being part of
  same group)
• Similarity (objects similar in
  appearance are perceived as being
  part of same group)
• Continuity (objects that form a
  continuous form are perceived as
  same group)
• Closure (like top-down
  processing…we fill gaps in if we can
  recognize it)
Constancy
     • Objects change in
       our eyes constantly
       as we or they
       move….but we are
       able to maintain
       content perception
     • Shape Constancy
     • Size Constancy
     • Brightness
       Constancy
          Perceived Motion
• Stroboscopic effect
  (flip book effect)
• Phi phenomenon
• Autokinetic Effect
  (if people stare at a
  white spotlight in a
  dark room, it
  appears to move.)
Depth Cues
     • Eleanor Gibson and her
       Visual Cliff Experiment.
     • If you are old enough to
       crawl, you are old enough
       to see depth perception.
     • We see depth by using
       two cues that researchers
       have put in two
       categories:
     • Monocular Cues
     • Binocular Cues
                Monocular Cues
• You really only need
  one eye to use these
  (used in art classes to
  show depth).
• Linear Perspective
• Interposition
• Relative size
• Texture gradient
• Shadowing
Binocular Cues
       • We need both of our
         eyes to use these cues.
       • Retinal Disparity (as an
         object comes closer to
         us, the differences in
         images between our
         eyes becomes greater.
       • Convergence (as an
         object comes closer our
         eyes have to come
         together to keep
         focused on the object).

				
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