Chapter 6 Perceiving the World

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Chapter 6Perceiving the World

• AP Psychology 2009-2010
• Mrs. Guerin T-9

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Chapter 6 Perceiving the World

• Textbook pages 212-248
• Study Guide pages 102-119
• Theme Perception is an active process
  perceptual impressions are not always accurate
  representations of events.

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Key Questions

• What are perceptual constancies, and what is
  their role in perception?
• What basic principles do we use to group
  sensations into meaningful patterns?
• How is it possible to see depth and judge
  distance?
• What effect does learning have on perception?

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Key Questions (continued)

• How is perception altered by attention, motives,
  values, and expectations?
• How reliable are eyewitness reports?
• Is extrasensory perception possible?

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Sensation vs. Perception

• Whats the difference?
• Sensation is the process of bringing information
  into the nervous system (Ch 5)
• Perception is the mental process of organizing
  sensations into meaningful patterns (Ch 6)

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Perceptual ConstanciesTaming an Unruly World

• size constancy the perceived size of an object
  remains the same, even though the size of its
  image on the retina changes
• EX
• Hold your left hand close to nose
• Hold your right hand at arms length

Hands look totally different sizes but we know
theyre the same
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Perceptual Constancies (continued)

• shape constancy the perceived shape of an
  object remains stable, even though the shape of
  its retinal image changes
• EX

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Perceptual Constancies (continued)

• brightness constancy the brightness of objects
  appears to stay the same as lighting conditions
  change
• EX
• White shirt still a white shirt whether in
• sun or shade

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Perceptual Constancies (continued)

• native vs. empirical
• inborn vs. learned
• (both affect perception)

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Perceptual OrganizationGetting It All Together

• Shhh.dont say it out loud - what do you see?

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Perceptual Organization (continued)

• figure-ground organization tend to see an
  object (figure) against a background (ground)
• reversible figures background and figure can
  switch

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Perceptual Organization (continued)
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Perceptual Organization (continued)
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Perceptual Organization (continued)

• GESTALT PRINCIPLES
• nearness (aka proximity)
• similarity
• continuation (aka continuity)
• closure
• contiguity
• common region

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Perceptual Organization (continued)

• Gestalt Principle of
• nearness (aka proximity) stimuli that are near
  each other are grouped together

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Perceptual Organization (continued)

• Gestalt Principle of
• similarity stimuli similar in size, shape,
  color, or form are grouped together

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Perceptual Organization (continued)

• Gestalt Principle of
• continuation (or continuity) perceptions tend
  toward simplicity and continuity

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Perceptual Organization (continued)

• Gestalt Principle of
• closure tendency to complete a figure so that
  it has a consistent overall form

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Perceptual Organization (continued)

• Gestalt Principle of
• contiguity nearness in time and space
  perception that one thing caused another
• EX
• knocking on your head at the same time as you
  (secretly) knock on a table sounds like your
  head is made out of wood

knock!
knock!
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Perceptual Organization (continued)

• Gestalt Principle of
• common region stimuli found within a common
  area tend to be seen as a group

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Designing for Human Use p217

• Engineering Psychologist
• Adapts machines for human use by making them
  compatible with our sensory and motor capacities
• http//www.edudecisions.com/articles/psychology/ps
  ychology-jobs/engineering-psychologist.php

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Perceptual Organization (continued)

• Camouflage patterns or designs that break up
  figure-ground organization
• EX
• Military uniforms (in battle), animals, insects.

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Perceptual Organization (continued)

• perceptual hypothesis an initial guess about
  how to organize sensations
• (We all do this to figure out what we see, but
  were not always correct)
• EX
• You see a friend in the distance only to realize
  when they get closer that its someone else

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Perceptual Organization (continued)

• ambiguous stimuli patterns that allow more than
  one interpretation
• EX
• Neckers cube

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Perceptual Organization (continued)

• impossible figure patterns that cannot be
  organized into stable, consistent, or meaningful
  perceptions
• EX three pronged widget

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Depth PerceptionWhat If the World Were Flat?

• depth perception the ability to see in 3D and
  judge distances
• Q Is depth perception learned or innate?
• A BOTH!

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Depth Perception (continued)

• Visual cliff a glass-topped table made to look
  like a cliff

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Depth Perception (continued)

• Depth cues features of the environment and
  messages from the body that supply information
  about distance and space
• Monocular cues work with just one eye
• Binocular cues require two eyes

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Depth Perception (continued)

• muscular cues come from the body
• accommodation (monocular cue) the bending of
  the lens to focus on nearby objects (sensations
  from muscles attached to each lens flow back to
  the brain
• convergence (binocular cue) the turning inward
  of both eyes to see something at a distance under
  50ft

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Depth Perception (continued)

• retinal disparity a discrepancy (difference) in
  the images that reach the right and left eyes
• stereoscopic vision perception of space and
  depth (3D) caused by the fact that the eyes
  receive different images

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random dot stereogram
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Depth Perception (continued)

• A Birds Eye View
• P223 in textbook

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Pictorial Cues for DepthA Deep Topic

• pictorial depth cues (all are monocular)
  features found in paintings, drawings, and
  photographs that impart information about space,
  depth, and distance

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Pictorial Cues for Depth (continued)

• Linear perspective
• Relative size
• Height in the picture plane
• Light and shadow
• Overlap (or interposition)
• Texture gradients
• Aerial perspective
• Relative motion (or motion parallax)

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Pictorial Cues for Depth (continued)

• Linear perspective convergence of parallel
  lines in the environment

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Pictorial Cues for Depth (continued)

• Relative size to depict two objects at
  different distances, the more distant object is
  smaller

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Pictorial Cues for Depth (continued)

• Height in the picture plane objects that are
  placed higher (closer to the horizon line) in a
  drawing tend to be perceived as more distant

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Pictorial Cues for Depth (continued)

• Light and shadow copying natural light patterns
  to create the appearance of a 3D picture

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Pictorial Cues for Depth (continued)

• Overlap (or interposition) when one object
  partially blocks another

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Pictorial Cues for Depth (continued)

• Texture gradients changes in texture also
  contribute to depth perception (texture gets
  smaller and finer in the distance)

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Pictorial Cues for Depth (continued)

• Aerial perspective smog, fog, dust, and daze
  add to the apparent distance of an object
  (distant objects tend to be hazy)

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Pictorial Cues for Depth (continued)

• Relative motion (or motion parallax) when
  looking out a window, closer objects seem to move
  more than objects that are farther away

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Pictorial Cues for Depth (continued)

• The Moon Illusion perceiving the moon as larger
  when it is low in the sky
• Apparent-distance hypothesis the horizon seems
  more distant than the night sky

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Pictorial Cues for Depth (continued)

• Ponzo Illusion the upper bar is the same length
  as the lower bar, but because the upper bar
  appears to be farther away than the lower bar, we
  perceive it as longer

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Perceptual LearningWhat If the World Were
Upside Down?

• Perceptual learning changes in the brain that
  alter how we process sensory information
  attributed to prior experience

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Perceptual Learning (continued)

• Perceptual habits well-established patterns of
  perceptual organization and attention that affect
  our daily experience

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Perceptual Learning (continued)
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Perceptual Learning (continued)

• The Ames Room

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Perceptual Learning (continued)

• Perceptual features lines, shapes, edges,
  spots, and colors (elements that the brain is
  especially sensitive to)
• Other-race effect the tendency to be better at
  recognizing faces from ones own racial group
  than faces from other racial or ethnic groups

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Perceptual Learning (continued)

• Active movement self-generated action
  (accelerates perceptual adaptation)
• EX Two groups wore goggles that distorted vision
• some walked on their own
• others were pushed around in wheelchairs
• those that walked adapted more quickly

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Perceptual Learning (continued)

• Context information surrounding a stimulus

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Perceptual Learning (continued)

• Frames of reference internal standards for
  judging stimuli
• Adaptation level the medium point of your
  personal frame of reference
• EX If asked to lift a 10 lb weight would you
  label it light, medium, or heavy?

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Perceptual Learning (continued)

• Illusion length, position, motion, curvature,
  or direction is consistently misjudged (but
  stimuli is real)
• http//dragon.uml.edu/psych/illusion.html
• Hallucination people perceive objects or events
  that have no external reality

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Perceptual Learning (continued)

• Stroboscopic movement motion perceived when
  objects are shown in rapidly changing positions
• strobe light on dance floor has the opposite
  effect freezes movement

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Perceptual Learning (continued)

• Muller-Lyer illusion

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Perceptual Learning (continued)

• Size-distance invariance the strict
  relationship between the distance an object lies
  from the eyes and the size of its image

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Motives and PerceptionMay I Have YourAttention!

• Pages 234 236
• Selective attention giving priority to a
  particular incoming sensory message
• Divided attention when you divide your mental
  effort among tasks, each of which requires more
  or less attention (limited capacity for storing
  thinking about info)

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Motives and Perception

• ATTENTION IS ALSO FREQUENTLY RELATED TO contrast
  OR change IN STIMULATION

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Motives and Perception

• Inattentional blindness failure to perceive a
  stimulus that is in plain view, but not the focus
  of attention
• Habituation a decrease in perceptual response
  to a repeated stimulus
• EX dripping faucet vs. ticking clock

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Motives and Perception

• Orientation response (OR) prepares us to
  receive information from a stimulus
• EX
• Pupils enlarge, brain-wave patterns shift,
  breathing stops briefly, blood flow to head
  increases, we turn toward stimulus, etc.

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Motives and Perception

• Boiled Frog Syndrome not being able to notice
  gradual changes in stimuli

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Perceptual ExpectanciesOn Your Mark, Get Set

• Bottom-up processing analyze info starting at
  the bottom with small sensory units (features)
  and build upward to a complete perception
• Top-down processing preexisting knowledge is
  used to rapidly organize features into a
  meaningful whole

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Perceptual Expectancies
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Perceptual Expectancies

• Perceptual expectancy (or set) a readiness to
  perceive in a particular manner, induced by
  strong expectations
• (past experience, motives, context, etc.)
• perceptual sets often lead us to see what we
  expect to see
• Perceptual category classes, types, groups

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Psychology in ActionPerception and Objectivity
Believing is Seeing

• (pages 239 242)
• Perceptual reconstruction
• Eyewitness
• Weapon focus
• Reality Testing
• Perceptual Awareness
• Attention

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A Step BeyondExtrasensory Perception Do You
Believe in Magic?

• (pages 243 246)
• ESP
• Parapsychology
• Psi Phenomena
• Clairvoyance
• Telepathy
• Precognition
• Psychokinesis
• Coincidence

• Zener Cards
• Fraud
• Skepticism
• Statistics and Chance
• Research Methods
• Replicate
• Ganzfield
• Stage ESP