What is Cognitive Science?

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What is Cognitive Science?
Zenon Pylyshyn, Rutgers Center for Cognitive
Science

• Whats in the mind that we may know it?

http//ruccs.rutgers.edu/faculty/pylyshyn.html
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Cognitive science is a delicate mixture of the
obvious and the incredible

• Granny was almost right
• Behavior really is governed by what we know and
  what we want (together with the mechanisms for
  representing and for drawing inferences from
  these)

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Its emic, not etic properties that
matterKenneth Pike

• What determines our behavior is not how the world
  is, but how we represent it
• As Chomsky pointed out in his review of Skinner,
  if we describe behavior in relation to the
  objective properties of the world, we would have
  to conclude that behavior is essentially
  stimulus-independent
• Every behavioral regularity (other than physical
  ones like falling) is cognitively penetrable

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Its emic states that matter!
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The central role of representation presents some
serious problems for a natural science

• What representations are about is what matters
• But how can the fact that a belief is about some
  particular thing have an observable consequence?
• e.g. How can the presence of holy grail in a
  belief determine behavior when the holy grail
  does not exist?
• In a natural science if X causes Y then X must
  exist and be causally connected to Y!
• Its even worse than that even when X exists, it
  is not Xs physical properties that are relevant!
  
• e.g., the North Star navigation

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This dilemma is sometimes referred to as
Brentanos problem or the problem of
intentionality

• What determines what we do is what our mental
  states are about, but aboutness is not a category
  of natural science.
• That is why Brentano concluded that psychology
  was beyond the grasp of natural science.

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There are other properties that are special to
cognitively determined behavior

• The Semantic determinants of most cognitive
  behavior. To capture regularities in
  cognitively-caused behavior we must use semantic
  terms terms referring to what things mean.
  Same-meaning stimuli are equivalent for many
  generalizations of cognitive science.
• The Cognitive Penetrability of most cognitive
  processes. Almost any regularity can be
  systematically altered in a quasi-rational way by
  imparting new information.

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Properties that are special about cognition

• The productivity and systematicity of systems of
  mental representation. Systems of mental
  representation are structured so that if they are
  capable of representing certain situations then
  they are also capable of representing an
  unbounded number of other related situations.
  This leads to the requirements that
  representations be compositional, and that they
  have constituent structure.
• The critical role of "Cognitive Capacity".
  Because of an organism's ecological or social
  niche, only a small fraction of its behavioral
  repertoire is ever actually observed. Nonetheless
  an adequate cognitive theory must account for the
  behavioral repertoire that is compatible with the
  organism's structure, which we call its cognitive
  capacity.

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Is it hopeless to think we can have a natural
science of cognition?

• Along comes The computational theory of mind
• the only straw afloat

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The major historical milestones

• Brentanos recognition of the problem of
  intentionality
• The formalist movement in the foundations of
  mathematics Hilbert, Goedel, Russell
  Whitehead, Turing, Church,
• Representational/Computational theory of mind
  Newell Simon, Chomsky, Fodor

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How to make a purely mechanical system reason
about things it does not understand or know
about? The discovery of symbolic logic.
(1) Married(John, Mary) or Married(John, Susan)
and the equation or statement, (2)
notMarried(John, Susan). from these two
statements you can conclude, (3) Married(John,
Mary) But notice that (3) follows from (1) and
(2) regardless of what is in the parts of the
equation not occupied by the terms or or not so
that you could write down the equations without
mentioning marriage or John or Mary or, for that
matter, anything having to do with the world.
Try replacing these expressions with the
meaningless letters P and Q. The inference still
holds (1') P or Q (2') not Q
therefore, (3') P
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Intelligent systems behave the way they do
because of what the represent

• But in order to function under physical
  principles, the representations must be encoded
  in physical properties
• How to encode knowledge in physical properties is
  by first encoding it in symbolic form (Proof
  Theory tells us how) and then instantiating those
  symbolic codes physically (computer science tells
  us how)

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Cognitive Science and the Tri-Level Hypothesis

• Intelligent systems are organized at three (or
  more) distinct levels
• The physical or biological level
• The symbolic or syntactic level
• The knowledge or semantic level
• This means that different regularities may
  require appeal to different levels

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Calculator example

• Why is the calculators printing faint and
  irregular? Why are parts of numbers missing in
  the LED display?
• Why does it take longer to multiply large numbers
  than small ones, whereas it takes the same length
  of time to add large numbers as small numbers?
• Why does it take longer to calculate
  trigonometrical functions than sums?
• Why is it especially fast at calculating the
  logarithm of 1?
• Why is it that when one of the keys (labeled ?)
  is pressed after a number is entered, the
  calculator prints what appears to be the square
  root of that number? Will it always do so?
• When the answer to an arithmetic problem is too
  long to fit in the display window, why are some
  of the digits left off?

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Does intentionality (and the trilevel hypothesis)
only apply to high-level processes such as
reasoning?

• Examples from vision.

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Does intentionality (and the trilevel hypothesis)
only apply to high-level processes such as
reasoning?

• Examples from color vision.

Red light and yellow light mix to produce orange
light This remains true for any way of getting
red light and yellow light e.g. yellow may be
light of 580 nanometer wavelength, or it may be a
mixture of light of 530 nm and 650 nm
wavelengths. So long as one light looks yellow
and the other looks red the law will hold.
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Does intentionality (and the trilevel hypothesis)
only apply to high-level processes such as
reasoning?

• Examples from language.

John gave the book to Fred because he finished
it John gave the book to Fred because he wanted it

• The city council refused to give the workers a
  permit for a demonstration because they feared
  violence
• The city council refused to give the workers a
  permit for a demonstration because they were
  communists

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Methodological asideOn the difference between
explanations that appeal to mental architecture
and those that appeal to tacit knowledge

• Suppose we observe some robust behavioral
  regularity. What does it tell us about the
  nature of the mind or about its intrinsic
  properties?

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An illustrative example Mystery Code Box
What does this behavior pattern tell us about the
nature of the box?
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The Moral Regularities in behavior may be due
to either

• The inherent nature of the system (to its
  structure), or
• The nature of what the system represents (what it
  knows).

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Where it matters

• Application of the architecture vs knowledge
  distinction to understanding what goes on when we
  reason using mental images

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Examples of behavior regularities attributable to
tacit knowledge

• Colour mixing, conservation of volume
• The effect of image size ?
• Scanning mental images ?

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Color mixing example
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Conservation of volume example
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Our studies of mental scanning
(Pylyshyn Bannon. See Pylyshyn, 1981)
There is even reason to doubt that one can
imagine scanning continuously (Pylyshyn Cohen,
1998)
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If cognition is at a different level of
organization than the physical level, how can we
ever tell what it is?

• We are limited only by the imagination of the
  experimenter, e.g.,
• Relative complexity evidence (RT, error rates)
• Intermediate state evidence
• Eye tracking
• Stage analysis (additive factors method)
• Event Related Potentials (EEG)
• fMRI
• clinical observations of brain damage
• Psychophysical methods (SDT)
• Etc

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Example of one methodology Sternberg memory
search paradigm
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Of course we cant always be sure we have the
right method or instrument
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If all else fails there is always parsimony and
generality(they worked well in physics and
linguistics!)