Visual Images

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Chapter 7

• Visual Images

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Answer the Following Questions

• How many windows are there on the front side of
  your house or apartment?
• When you enter your house, is the door knob on
  the right or the left?
• What is in the back seat of your car?
• On a regular clock, will the hands make a
  smaller angle at 320 or 725?
• Does George Bush wear glasses?

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Did you construct a mental image to help you
answer the questions?
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Did you construct a mental image to help you
answer the questions?
If you are like most people you did. This
illustrates the importance of visual imagery
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Early Research Suggesting the Importance of
Visual Imagery for Memory
Picture Superiority Effect Pictures tend to be
better remembered than their verbal labels.
Cup
Glass
vs.
Chair
Ball
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Early Research Suggesting the Importance of
Visual Imagery for Memory
Concreteness Effect Concrete words tend to be
better remembered than abstract words
Dog Lamp Tree Lake
Cause Fault Worth Phase
vs.
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Both findings invite the conclusion that visual
imagery enhances memory
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Paivios Dual Coding Hypothesis

• Two coding systems in long-term memory
• verbal code Specially adapted to handle
  linguistic stimuli
• non-verbal (visual) code Specially adapted to
  handle non-linguistic stimuli
• Coding systems are independent but interrelated.
• Dual coding (coding something both verbally and
  non-verbally) results in better memory.

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Availability of different codes
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Codes also differ with regard to their
organizational structure

• Verbal code -- sequential
• Non verbal code -- spatial

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A test of dual coding hypothesis
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Results
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Research on Mental Imagery
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Roger Shepards study of mental rotation

• Participant shown two drawings
• Participant instructed to indicate as quickly
  (and accurately) as possible if the two drawings
  were the same or if they were different.

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Roger Shepards study of mental rotation

• Participant shown two drawings
• Participant instructed to indicate as quickly
  (and accurately) as possible if the two drawings
  were the same or if they were different.

Same
Different
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Independent variable was the degrees of rotation
Same
Different
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Illustration of procedure
Indicate as quickly as you can whether a pair is
same or different
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Results
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Conclusion
Manipulating objects mentally is analogous to
manipulating them physically.
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Kosslyns study of mental travel
Participants committed this map to memory
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Kosslyns study of mental travel

• After committing the map to memory, participants
  were asked to focus on a particular location
  while visualizing the map.
• After a 5 sec delay, participants were given a
  second location on the map and were asked to scan
  the map for that new location.
• Participants indicated when they had moved to
  the new location by pushing a button.
• The time to travel from the first location to
  the second was recorded.

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Results
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Brooks study of visual interference
Participants asked to visualize a block letter
such as
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Brooks study of visual interference
Participant was instructed to mentally travel
around the figure starting from the asterisk and
going in the direction of the arrow
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Brooks study of visual interference
Each time the participant reached a corner, he or
she was to say yes if the corner was at the top
or bottom and no otherwise.
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Demonstration
Commit the following letter to memory
When I say go I want you to travel around the
letter in your mind. Each time you reach a
corner, indicate if the corner is at the top or
bottom by saying yes. Say no when the corner
is not at the top or bottom. Complete this task
as quickly as you can without making errors.
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Go!
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Now do it again with the following letter (note
new starting location and direction). This time
however, indicate your answer by pointing to a
Y (for yes) or a N (for no) on this page.
Each time you must point to a new Y or N.
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Go!
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Conclusion
The fact that it is more difficult to perform the
task when one must respond by pointing to letters
suggests that the visual processing involved in
looking (and pointing) at letters interferes with
ones ability to maintain a mental image. This
raises the possibility that mental imagery
involves some of the same brain structures as
those used in seeing.
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PET scan studies
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Basic methodology

• Radio active marker injected into blood stream.
• This allows one to monitor blood flow in the
  brain
• Those parts of the brain that are more active
  require more blood

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Sample PET scan
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Method

• Participant engages in one of following tasks
• mental arithmetic (count backward by 3s)
• memory scanning of auditory stimulus (saying
  every other word in a well known jingle)
• memory scanning of a visual stimulus (imagining a
  walk in ones neighborhood)
• PET scans recorded

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Critical finding
PET scan revealed increased blood flow to
posterior portions of brain, particularly the
visual cortex when the participant engaged in
memory scanning of a visual stimulus. These are
the same areas that typically show increased
blood flow during a visual-perceptual task
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Studies of cortical blindness
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Cortical blindness refers to visual impairment
that results from damage to the visual areas of
the cortex.
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Cortical blindness refers to visual impairment
that results from damage to the visual areas of
the cortex. Often the impairment can be quite
specific such as not being able to see color, not
being able to identify visually presented
objects, or not being able to locate objects in
the visual field
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Interesting Finding
These individuals display impairments in imagery
ability that seem to mirror their impairment in
visual ability.
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Examples
Patients who lack color vision cant answer such
questions as What color is a tangerine or What
color is cement.
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Examples
Patients who lack color vision cant answer such
questions as What color is a tangerine or What
color is cement.
Patients who cant recognize visually presented
objects cant draw them from memory (although
they can draw a detailed map of the locations of
objects).
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Conclusion
These studies reinforce the notion that the
construction of mental images involves the same
neurological structures that are involved in
visual perception.
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Is visual imagery necessarily visual?
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Is visual imagery necessarily visual?
Studies with the congenitally blind suggest that
visual imagery might not necessarily be visual.
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Findings

• The results of mental rotation experiments using
  tactilely presented stimuli produce the same
  results in people with congenital blindness
• The results of mental travel experiments using
  tactilely presented maps also produce the same
  results

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Does photographic memory exist?
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Can you pick out the real penny?
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What does this demonstration imply about
photographic memory?
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Reality Monitoring
Did it really happen or did I just imagine it?
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A paradigm for studying reality monitoring

• Participants presented pictures of familiar
  objects either 2, 5, or 8 times.
• Participants presented words of same familiar
  objects either 1, 5, or 8 times.
• When a word is presented, the participant is
  asked to construct a mental image of the word.
• Participants shown pictures and asked to judge
  how many times they saw each picture.

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Experimental Design
Number of times word is presented (Number of
image trails)
2
5
8
2
5
Number of times picture is presented
8
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Breakdown in Reality Monitoring
When imagined events become real a source of
false memories.
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Factors that contribute to false memories

• A long delay between the event and the attempt to
  remember
• Repeated suggestions that the event occurred
• Perceived authority of the source of suggestions
• Perceived plausibility of the event
• Mental rehearsal of the imagined event
• The use of mental imagery or guided rehearsal

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A representative study

• Participants (college students) were asked to
  recall early childhood events, one of which was
  false.
• Participants were assigned either to an imagery
  condition or a control condition
• Participants in the imagery condition were more
  likely to remember the false event.