Imagery

1
Imagery

• Visual perception allows us to inspect, reach
  for, manipulate objects and navigate around them.
• Visual imagery is analogous to perception in that
  it can be used to represent and process
  information about objects, in the mind.
• There is a connection, but they are not the same.
  
• Mental tasks, thinking, are undertaken in
  Imagery. (see the R test)

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Imagery

• Necker Cube

• Cooper Shepherd 1973

Which of these figures are correct?
3
Ancient history

• The earliest written languages were in the form
  of pictorial symbols.
• Many philosophers from Aristotle through
  Descartes and Locke assumed that picture-like
  images were an essential part of human thought
  .Thagard
• Greek orators used imagery-based mnemonic devices
  to help them remember the sequence of events when
  reciting long oral traditions. Anderson
• Plato likened memory representations to
  impressions on a wax tablet thereby becoming one
  of the first to distinguish between the
  representations and the medium in which they
  occur. Pylyshyn, 1981

4
More recently

• 1880s Sir Francis Galton provided the first
  psychological documentation that individuals vary
  greatly in the vividness of their visual imagery.
• 1889-1913 Psychologists focused on the study of
  Imagery, but their techniques were so flawed that
  by
• 1920 with the rise of Behaviorism, the
  experimental study of the mind fell into abeyance.

5
1960s

• Interest in mental imagery was revived when Alan
  Paivio 1986 started a program of study of the
  facilitating effects of imagery-related variables
  on the performance of memory.
• He formulated a dual-coding theory about the
  representation of knowledge in memory a verbal
  system specialised for processing verbal
  materials,logogens, and a non-verbal one, for
  objects and events, with imagens.

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The study of Imagery.

• Mental images are subjective thus developing a
  cognitive understanding of Imagery has been
  fraught with difficulties.
• There are visual, auditory, motor, gustatory,
  olfactory images. This discussion is confined to
  visual images.
• Researchers have been forced to develop
  experimental procedures that allow them to make
  inferences from behavior and neuro-physical
  states.

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Some questions to be answered in a Theory of
Imagery

• How are mental representations processed and
  transformed?
• What is the structure/nature of mental images?
  Are they pictorial or not?
• What is the relationship between imagery and
  perception?
• How do we account for individual differences in
  imagery ability?

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The pictorialists, many of whom are
neuro-scientists

• Believe that picture-like displays are generated
  on the surface of the visual cortex during
  imaging.
• Have taken a Bottom-up approach to research on
  Imagery.
• Research in different paradigms to understand
  mental organization and investigate manipulation
  of representations.

9
Martha Farah et al 1992 in studies on brain
damaged patients found that

• A person who developed tunnel vision after
  unilateral occipital lobocectomy also developed
  tunnel imagery.
• One patient who had disassociation of recognition
  abilities and spatial relations could not
  identify a known object, but could manipulate it
  another could identify, but not process spatial
  relationships.
• Eduardo Bisiach et al found that patients with
  unilateral visual neglect also suffered from
  comparable neglect in imagery.

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Shepherd and Podogorny Anderson

• They reported that perceptual and imaging
  versions of the same task yielded the same
  pattern of results.
• Their studies included an exercise about whether
  a presented dot fell on a target block letter.

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Tversky 1991

• People can transform an initial image by gradual
  means by letting it fade then bringing up the
  transformed image.
• Or they may blink and start again as this
  requires less effort.
• Imagery is likely to be used in fact retrieval if
  the fact is about a visual property that a person
  has seen and it has not been considered
  frequently in the past.

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Holly and Taylor studies

• Subjects given route or survey text descriptions,
  with landmarks, of an area, were asked
  verification questions.
• There was no significant difference between
  responses for route and survey subjects.
• When these subjects were asked to draw a map,
  they remembered the landmarks in order of mention
  in the text.
• Findings were that subjects appeared to mentally
  move through a sort of 3-D model of space which
  has no perspective. These findings differ from
  the classic work on imagery which is
  perception-like and from a particular point of
  view.

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Spatial Frameworks Tversky, 1991

• Studies done where the subject images himself at
  the top of an escalator and is given information
  about spaces around him. It was found that rather
  than turning around, people construct spatial
  frameworks (scaffolding) - with most rapid access
  to information in front and up and down, then on
  left and right.

14
Kosslyns 1994 theory has gained general
acceptance.

• Visual images are depictive representations that
  can be manipulated, interpreted and
  re-interpreted so that people can extract novel
  information about object properties.

15
Kosslyn parts of the brain used in visual
perception are also involved in visual mental
imagery.

• Using Positron Emission Tomography (PET) it was
  demonstrated that the primary visual cortex is
  activated when people image objects with their
  eyes closed.
• The pathway from the primary visual cortex to
• the parietal lobe (upper back part) processes
  object properties such as shape, color and
  texture.
• the temporal lobe (back part) processes spatial
  properties needed for manipulation or navigation
  such as size location and orientation of objects.

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Kosslyn cont.

• Imagery is high level visual perception- it
  incorporates the use of knowledge about objects
  and events and top-down hypothesis-testing
  mechanisms to recognize objects under varying
  conditions.

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Percepts and images are patterns of activity in
a visual buffer, a topographically-mapped area in
the primary visual cortex. Kosslyn

• My Sketch

Image inspection carried out with processes used
to encode and interpret perceptions
The visual buffer is in the primary visual
cortex. The pattern of activity is transient.
Visual buffer

Associative memory stores visual images. Must be
re-activated continuously to maintain images
Attentional subsystems-draw images in buffer
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Logies model of visuo-spatial working memory
Central executive Where conscious images are
generated and manipulated
Spatial info in temporary storage
Visual info in temporary storage

Visual info in long term memory
Spatial info in long term memory
The inner scribe who manipulates the storage
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Images are epiphenomenal.Pylyshyn 1970 to
the present

• Reasoning with mental images involves the same
  form of representations and the same processes as
  that of reasoning in general.
• However, the content or subject matter of
  thoughts experienced as images includes
  information about how the things would look.
• Images, though real, are epiphenomenal and do not
  serve any useful function.

20
John Anderson late 1970s

• Neither theoretical structures nor processes can
  be firmly anchored by behavioral data alone, thus
  any depictive theory can be reformulated as a
  propositional one.
• (propositional statement in language or symbols)

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Bibliography

• Kosslyn, S.M. 1981. The medium and the message in
  mental imagery a theory. Psychological Review
  88. 46-66.
• Thagard, Paul. 2000. Mind. Introduction to
  Cognitive Science. 3ed. MIT Press.
• Tversky, B. 1991. Spatial mental models. In G.H.
  Bower (ed) The Psychology of Learning and
  Motivation 27. N.Y. Academic Press. 109-145
• Bechtel, W and George Graham (eds) 1998. A
  Companion to Cognitive Science. Mass., Blackwell
  Publishers