Sensation+and+Perception by xiangpeng

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									Sensation and
 Perception

     Unit 5
 Meyers: Ch. 5,6
 Barrons: Ch. 4
 Passer/Smith:
     Ch. 5
          Stimulus Detection
• Sensory systems are a means by which the
  human body interacts with the outside
  environment.
• Sensory organs capture a certain type of energy.
  Must be of sufficient quantity to be perceived.
• Energy Types:
  – Eye: Electromagnetic
  – Ear: Expanding and compressing molecules of air
    (waves)
  – Nose and Tongue: airborne or substance chemicals
  – Skin: pressure, temperature, and pain
Sensation
       1. Stimulus is received by sensory receptors

       2. Receptors translate stimulus properties into
          nerve impulses (transduction)

       3. Feature detectors analyze stimulus features

       4. Stimulus features are reconstructed into
          neural representation

       5. Neural representation is compared with
          previously stored information in brain

       6. Matching process results in recognition and
          interpretation of stimulus

Perception
                            Absolute Threshold
                     Sensation -> TRANSDUCTION -> Perception
Sense Organ   Layman‟s   Scientist‟s   Universal    Specific       Transduced    Absolute
              Term       Term          Energy       Transduction   into What?    Human
                                       Source       Site                         Threshold
1




2




3




4




5




6                                      Vestibular                  Kinesthetic
                                       Sense:                      Sense:
Sensory Systems: Transduction
• Visual Sense:
Sensory Systems: Transduction
Sensory Systems: Transduction
Sensory Systems: Transduction
          Sensory Processes
• Signal Detection Theory: the point of our
  „detection‟ of a stimulus varies depending on
  a number of factors, including: experience,
  other environmental stimuli fatigue,
  expectation, significance of stimulus

                   • Subliminal Stimuli: Can you
                     learn while you are asleep?
                     Not really… placebo effect
                     has more relevance than
                     sensation. The sensory
                     stimuli are present, but the
                     brain cannot „perceive‟ it
        Difference Threshold
• The point at which the brain has, in fact,
  perceived a stimuli after the absolute
  threshold has been met.
  – Also called the Just Noticeable Difference.
  – Habituation can cause even higher JNDs: the
    brain “gets used to” certain non-threatening
    environmental stimuli and tunes them out.
                   Perception
Bottom-up Processing:      Top-down Processing:
  bringing data from the    what the brain layers
  peripheral nervous       on top of the raw data
  system as raw data to      to create perception
  the brain
                                       Experience

                                                Other
                                            Environmental
                                               Stimuli

                                            Expectations

                                            Knowledge

                                     Etc.
                  Perception
• Attention: priority is given first to things that are
  life-threatening, to the exclusion of other stimuli
• Organization and Structure: the brain loves
  order! It takes millions of pieces of information
  and makes a “meaningful whole” out of them.
  Example: Cloud watching




• Illusion: when our perception is incorrect (i.e.,
  the brain‟s assembly has arrived at the wrong
  result)
                   Perception
• Hypothesis Testing: the brain searches for meaning,
  looking for similar data in your memories
                   Perception
• Hypothesis Testing: the brain searches for meaning,
  looking for similar data in your memories
                Perception
• Perceptual Constancies: we cannot attend to
  everything in our environment. Perceptual
  constancy keeps certain things constant even
  as they are changing.
Perception
    • Depth Perception: it‟s
      not just an ocular
      phenomenon, it
      includes experience
      and physical
      maturation
      – Adding all of it up turns
        2-D data into a 3-D
        image.
Perception of Depth, Distance, and
            Movement
• Distance
  Perception:
  Monocular cues
  refer to the
  perception that
  parallel lines
  converge as they
  recede.
Illusions
     • An inaccurate
       perception based on
       sensory data. Because
       the data is always
       incomplete, the brain
       fills in the holes with
       experience and
       expectation.

     • Sometimes, it‟s wrong.
  Experience, Critical Periods, and
     Perceptual Development
• Perceptual Development: Since the brain draws on
  experience and expectation (also based on experience),
  young children often encounter sensory stimuli that the
  brain does not know how to process. Thus, the brain‟s
  inability to perceive certain things.

               • Critical periods are
                 periods during
                 which the brain is
                 „primed‟ and open
                 to new experience,
                 but after which the
                 brain has moved on
                 and will not be able
                 to perceive.
Restored Sensory Capacity
      Taking into account how much
       the brain relies on
       experience, and the fact that
       critical periods limit the
       brain‟s ability to acquire new
       ways of interpreting data,
       what would have happened if
       Helen Keller had undergone
       surgery to restore her sight
       as an adult?

								
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