Sensation%20and%20Perception

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Chapter 4Perception
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Basic Principles of PERCEPTION

• Perception is the process that organizes those
  stimuli into meaningful objects and events and
  interprets them.

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Sound Localization

• Sound localization the ability to locate objects
  in space solely on the basis of the sounds they
  make
• Because the ears are only 6 inches apart, the
  time lag between the sound reaching both ears is
  very short.
• Even such small time lags provide the auditory
  system with sufficient information to locate the
  sound.

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Sound Localization
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Pitch Perception Place Theory

• Place theory contends that we hear different
  pitches because different sound waves trigger
  hair cells on different places of the cochleas
  basilar membrane.

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Pitch Perception Frequency Theory

• Frequency theory contends that pitch is
  determined by the frequency with which the
  basilar membrane vibrates.

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Pitch Perception

• Place theory best explains high-frequency sounds,
  while frequency theory best explains
  low-frequency sounds. Mid-frequency sounds are
  best explained by volley theory, a revision of
  frequency theory.

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Visual Perception

• Organization and interpretation of incoming
  visual information.

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Pathways from the Eyes to the Visual Cortex
(Left-Right Visual Fields)
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Visual Information Processing

• Feature Detectors
• nerve cells in the brain that respond to specific
  features of the stimulus
• shape
• angle
• movement

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Young-Helmholz Trichromatic Theory of Color Vision

• Any color can be created by combining three
  primary colorsred, green, and blue.
• The retina has three types of color receptors
  that produce the primary color sensations of red,
  green, and blue.

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Additive and Subtractive Color Mixing
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Color Vision
LO 3.3 How Eyes See and How Eyes See Color

• Trichromatic theory theory of color vision that
  proposes three types of cones red, blue, and
  green
• Afterimages images that occur when a visual
  sensation persists for a brief time even after
  the original stimulus is removed

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Color Vision
LO 3.3 How Eyes See and How Eyes See Color

• Opponent-process theory theory of color vision
  that proposes four primary colors with cones
  arranged in pairs red and green, blue and yellow
• lateral geniculate nucleus (LGN) of thalamus

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Opponent Process Flag
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Opponent Process Flag

• Explanation Color AfterimageStare at
  the white dot in the center of this oddly colored
  flag for about 30 seconds. Now look at a white
  piece of paper or a white wall. Notice that the
  colors are now the normal, expected colors of the
  American flag. They are also the primary colors
  that are opposites of the colors in the picture
  and provide evidence for the opponent-process
  theory of color vision.

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Color Blindness
LO How Eyes See and How Eyes See Color

• Monochrome colorblindness a condition in which a
  persons eyes either have no cones or have cones
  that are not working at all
• Red-green colorblindness either the red or the
  green cones are not working
• protanopia lack of functioning red cones
• deuteranopia lack of functioning green cones
• tritanopia lack of functioning blue cones

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The Ishihara Color Test
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The Ishihara Color Test

• In the circle on the left, the number 8 is
  visible only to those with normal color vision.
  In the circle on the right, peoplewith normal
  vision will see the number 96, while those with
  red-green color blindness will see nothing but a
  circle of dots.

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Perceptual OrganizationNecker Cube

• Gestalt
• an organized whole
• tendency to integrate pieces of information into
  meaningful wholes

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Gestalt Principles
LO 3.9 Gestalt Principles of Perception

• FigureGround
• the tendency to perceive objects, or figures, as
  existing on a background
• Reversible Figures
• visual illusions in which the figure and ground
  can be reversed

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Perceptual Organization

• Figure Ground
• Organization of the visual field into objects
  (figures) and surrounding background (ground)

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Gestalt Principles
LO 3.9 Gestalt Principles of Perception

• Similarity
• the tendency to perceive things that look similar
  to each other as being part of the same group
• Proximity
• the tendency to perceive objects that are close
  to each other as part of the same grouping

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Gestalt Principles
LO 3.9 Gestalt Principles of Perception

• Closure
• the tendency to complete figures that are
  incomplete
• Continuity
• the tendency to perceive things as simply as
  possible with a continuous pattern rather than
  with a complex, broken-up pattern

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Gestalt Principles
LO 3.9 Gestalt Principles of Perception

• Contiguity
• the tendency to perceive two things that happen
  close together in time as being related

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Depth Perception

• Depth perception the ability to perceive objects
  three-dimensionally
• Binocular cues depth cues that require
  information from both eyes
• Monocular cues depth cues that require
  information from only one eye

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The Visual Cliff
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Depth Perception Binocular Cues

• Binocular cues- depend on use of two eyes
• retinal disparity
• images from the two eyes differ
• closer the object, the larger the disparity
• convergence
• neuromuscular cue
• two eyes move inward for near objects

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Monocular Cues
LO 3.10 What Is Depth Perception?

• Monocular cues (pictorial depth cues) cues for
  perceiving depth based on one eye only
• linear perspective the tendency for parallel
  lines to appear to converge on each other
• relative size perception that occurs when
  objects that a person expects to be of a certain
  size appear to be small and are, therefore,
  assumed to be much farther away

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Monocular Cues
LO 3.10 What Is Depth Perception?

• Monocular Cues (contd)
• interposition (overlap) the assumption that an
  object that appears to be blocking part of
  another object is in front of the second object
  and closer to the viewer

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Linear Perspective
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linear perspective.
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Relative Size
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Overlap or Interposition
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Monocular Depth Cues
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Monocular Depth CuesHeight in Visual Field
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Monocular Cues
LO 3.10 What Is Depth Perception?

• Aerial perspective the haziness that surrounds
  objects that are farther away from the viewer,
  causing the distance to be perceived as greater
• Texture gradient the tendency for textured
  surfaces to appear to become smaller and finer as
  distance from the viewer increases

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Texture gradient causes the viewer to assume that
as the texture of the pebbles gets finer, the
pebbles are getting farther away Notice how the
larger pebbles in the foreground seem to give way
to smaller and smaller pebbles near the middle of
the picture. .
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Texture Gradient
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In aerial or atmospheric perspective, the farther
away something is the hazier it appears because
of fine particles in the air between the viewer
and the object. Notice that the road and
farmhouse in the foreground are in sharp focus
while the mountain ranges are hazy and indistinct.
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Monocular Cues
LO 3.10 What Is Depth Perception?

• Motion parallax the perception of motion of
  objects in which close objects appear to move
  more quickly than objects that are farther away
• Accommodation as a monocular clue, the brains
  use of information about the changing thickness
  of the lens of the eye in response to looking at
  objects that are close or far away

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Perceptual Constancy

• perceiving objects as unchanging despite changes
  in retinal image
• color
• shape
• size

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Shape Constancy
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Size-Distance Relationship
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Perceptual Illusions Ames Room
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Size-Distance Relationship
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The Müeller-Lyer Illusion
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Müller-Lyer Illusion
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Perceptual Set

• a mental predisposition to perceive one thing
  and not another
• expectations that create a tendency to interpret
  sensory information in a particular way

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Cultural Influence on Perception
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Perceptual Set

• What you see in the center is influenced by
  perceptual set

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Would you have interpreted the middle drawing
differently if you had looked at the drawing of
the mans face or the sitting woman first?
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Perceptual Set
Flying Saucers or Clouds?
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There Is Little Scientific Evidence for
Extrasensory Perception

• Extrasensory perception (ESP) the ability to
  perceive events without using normal sensory
  receptors
• Parapsychology the field that studies ESP and
  other paranormal phenomena

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There Is Little Scientific Evidence for
Extrasensory Perception

• Types of ESP
• Mental telepathy the ability to perceive others
  thoughts
• Clairvoyance the ability to perceive objects or
  events that are not physically present
• Precognition the ability to perceive events in
  the future
• Psychokinesis the ability to control objects
  through mental manipulation

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Is There Extrasensory Perception?

• Extrasensory Perception
• controversial claim that perception can occur
  apart from normal sensory input
• trickery (magician)
• imagination
• paranormal forces?????
• Not a natural human ability

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There Is Little Scientific Evidence for
Extrasensory Perception

• Reasons for skepticism include
• Generally, findings supporting the existence of
  paranormal abilities cannot be replicated in
  subsequent research.
• Many published ESP studies have used flawed
  research methodologies or failed to detect
  outright fraud by those they were testing.

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There Is Little Scientific Evidence for
Extrasensory Perception

• Until ESP phenomenon can be reliably replicated
  in carefully controlled scientific studies, it
  will remain only a highly speculative
  extra-sense to most practitioners of science.