Perceptual Symbol Systems

1
Perceptual Symbol Systems

• Joey Bokor
• Patrick Yaner

2
Grounding Cognition in Perception

• Claim Cognition is inherently perceptual
• A common representational system underlies
  perception and cognition
• From Aristotle to Locke to Kant, theorists over
  the last 2000 years have viewed cognition as
  imagistic in nature

3
Grounding Cognition in Perception

• Image-based theories disappeared as behaviorists
  and language philosophers began to shy away from
  mental states
• Recently, cognitive scientists have been working
  with representational schemes that are inherently
  nonperceptual, or amodal

4
Problems with amodal systems

• Little direct empirical evidence that amodal
  systems exist
• Failure to provide a satisfactory account of the
  transduction process that maps perceptual states
  into amodal symbols
• Also the converse, the symbol grounding problem
• Too powerful able to explain any finding
  post-hoc, but often without much illumination

5
Perceptual States

• Arise in sensory-motor systems
• Two components
• Unconscious neural representation of physical
  input
• Optional conscious experience

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Perceptual Symbols

• The structure of a perceptual symbol corresponds
  (at least somewhat) to the perceptual state that
  produced it
• Note this does not claim that a perceptual
  symbol corresponds to the physical world

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Perceptual Symbols Are Not

• Like physical pictures
• Mental images
• Any other form of conscious subjective experience
• The record of the entire brain state that
  underlies a perception

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Perceptual Symbols Are

• Partial records of the neural states that
  underlie perception
• Dynamic, not discrete
• Not necessarily representative of specific
  individuals
• Potentially indeterminate

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Systems of Perceptual Symbols

• Related perceptual symbols combine to form
  simulators that allow the cognitive system to
  construct specific simulations of an entity or
  event in its absence

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Simulators

• Composed of frames and the simulations that the
  frame produces
• The figure shows a partial frame for car and
  illustrates how the frame changes dynamically

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Simulations

• Simulations are always partial and sketchy, never
  complete
• Simulations are likely to be biased and distorted
  in various ways, rarely, if ever veridical
• A simulator goes beyond a simple empirical
  collection of sense impressions. It is both
  rational and empirical, reflecting intertwined
  genetic and experiential histories.

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Simulators

• Two levels of structure
• A deep set of generating mechanisms (typically
  unconscious)
• These produce an infinite set of surface images
  (typically conscious)

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Concepts and Simulators

• A concept is equivalent to a simulator
• If we have an appropriate simulator of something,
  then it can be said that we understand the
  concept
• Thus the primary goal of human learning is to
  establish simulators

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Summary

• Perceptual states arise in the sensory-motor
  system
• A subset of the state is extracted by selective
  attention and stored in long-term memory
• This perceptual memory can function as a symbol
  entering into symbol manipulation
• Collections of the perceptual symbols comprise
  our conceptual representations

15
Problems with PSS

• Adams Campbell
• Three criticisms
• Significantly incomplete description of a
  simulator
• No demonstration that the activated neural
  connections are constitutive of the relevant
  concepts. Empirical evidence suggests activation
  while thinking of a concept, however what proof
  is there that the activations that form a
  Perceptual Symbol and are not simply a byproduct
  of thinking
• Failure to account for abstraction truth, anger
  etc.

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Problems with PSS

• Brewer
• the ontological status of perceptual symbols is
  unclear and this form of representation doesnt
  account for all forms of human knowledge
• abstract constructs such as entropy, democracy
  and abstract
• (non model) scientific theories such as evolution
  and quantum mechanics
• gist recall in abstract schemes
• logical words such as but, therefore and because
• language form
• the underlying argument structure of his own
  article

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Problems with PSS

• Dennet Viger
• Sort-of Symbols
• What kind of things are thoughts, and how do you
  make em out of brainstuff?
• Similarly what does it mean to think in
  perceptual symbols
• Paper provides the specs but not yet a model for
  PSS

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References

• Barsalou, L. W. (1999). Perceptual Symbol
  Systems. Behavioral and Brain Sciences 22
  507-569.
• Barsalou, L. W. (1999). Perceptions of
  Perceptual Symbols. Authors response to Open
  Peer Commentary, in Behavioral and Brain Sciences
  22 637-660.
• Adams, Fred and Campbell, Kenneth (1999).
  Modality and abstract concepts. Commentary on
  L.W. Barsalou, Perceptual Symbol Systems in
  Behavioral and Brain Sciences 22 610.
• Brewer, William F. (1999). Perceptual symbols
  The power and limitations of a theory of dynamic
  imagery and structured frames. Commentary on
  L.W. Barsalou, Perceptual Symbol Systems in
  Behavioral and Brain Sciences 22 611-612.
• Dennet, Daniel C. and Viger, Christopher D.
  Sort-of Symbols? Commentary on L.W. Barsalou,
  Perceptual Symbol Systems in Behavioral and Brain
  Sciences 22 613.