Brain Imaging, Averaging, and the Evidence of Mechanisms

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Brain Imaging, Averaging, and the Evidence of
Mechanisms

• Clark Glymour

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My Question

• Can we infer brain mechanisms producing cognitive
  activities from imaging data if, to enhance the
  signal, we average image signals over several
  subjects and times?
• But first a detour through
• Metaphilosophy
• Bayes Nets
• Genetics

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PART I
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Critical Prolegomena Against Philosophers on
Mechanism

• The Platonic Form for Philosophy Fill in the
  Blanks.
• The concept of X is to be understood as follows
• Necessarily, X if and only if
• ---- ---- .----

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The Extremal Version

• Christopher Peacocke
• Oxford philosophers know the Platonic Forms of
  cognitive concepts. The business of psychology
  should be to illustrate their analyses
  experimentally (Turing Colloquium)
• Colin McGinn
• Nothing is Philosophy unless it provides an
  analysis of a concept in Platonic Form. (Review
  of Annette Baier, New York Review of Books)

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The Contemporary Socratic Conversation

• Necessarily, X if and only if A B C
• Oh, and let me tell you about an example
  exothermic ion fusion
• Counterexample X A and B and C
• Necessarily, X if and only if A B D
• Oh, and let me tell you about another example
  endothermic plasmic membrane transport
• Counterexample X A and B and D from 18
  dimensional Kruskal space time
• Necessarily, X if and only if A B D
• We were talking about X not X
• Necessarily, X if and only if A and and B and D
  and (Obscurity)
• One can imagine something S that is A, B, D and
  (Obscurity) that is not an X
• No, one cannot S does not have (Obscurity)
• Etc.

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Example Analyses of Mechanism

• A mechanism underlying a behavior is a complex
  system which produces that behavior by of the
  interaction of a number of parts according to
  direct causal laws. (Glennan 1996, 52).

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Maybe there are no relevant laws

• A mechanism for a behavior is a complex
  system that produces that behavior by the
  interaction of a number of parts, where the
  interactions between parts can be characterized
  by direct, invariant, change-relating
  generalizations (Glennan 2002b, S344).

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What the Hell, cause and productive arent
obscure enough, lets throw in activities

• Mechanisms are entities and activities
  organized such that they are productive of
  regular changes from start or set-up to finish or
  termination conditions (Machamer, Darden, Craver
  2000, 3).

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And, change X to X in the counterexamples

• But not all effects are produced by reliable
  mechanisms. Satisfactory mechanistic
  explanations can sometimes be given for effects
  resulting from mechanisms whose operations are
  too irregular to enable us to reliably predict
  their future performance, or to systematically
  explain why they sometimes fail to produce the
  effects they produce on other occasions. For
  example, you can explain what gets a chain saw
  started even if its an old chain saw that starts
  infrequently and irregularly. (Bogen, my italics)

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Which are mechanisms?

• The particles of a gas and their motiona
  mechanism for temperature?
• Kids at recessa mechanism for yelling?
• A governor on a throttlea mechanism for
• limiting speed?
• Cruise controla mechanism for keeping speed from
  changing?
• A fusea mechanism for limiting current?
• Smilinga mechanism for producing smiles in
  others?
• The universea mechanism for expansion?
• A stone against a tirea mechanism for keeping
  the car from rolling?

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What causal processes or relations or arent
mechanisms?
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The Platonic Form

• Never led to any Important Discovery of Anything
  because
• Lots (ok, almost all) of fundamental concepts
  have no informative definition of the Platonic
  Form number, force, computable function, cause,
  explanation, etc.
• Vagueness and variation of usage
• Nothing interesting can be deduced from a
  conjunction of simple, often vague, predicate
  phrases

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Ad Hominem Why Does It Continue?

• Its what philosophers know how to do
• No encroachment, since no other discipline except
  philology wants to make such an activity its
  focus
• Makes work, because there are no answers as fine
  as philosophers insist on
• Esoterica divert attention to scientific details
  and away from the triviality of the theories
  (Compare art critcism)

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The Platonic Form

• Is at best a Prolegomena, a gloss, a
  specification of topic, for something more
  substantialwhich requires work

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Judah Pearl Why dont philosophers do any work?

• What sort of work?
• Abstractionbecause otherwise we only have
  examples, nothing general, and because thats
  philosophy
• Approximationbecause approximation is the soul
  of progress
• Formalizationenough so one knows what a
  consequence of the assumptions would be
• Proofof interesting consequences
• Applicationso one knows the consequences matter

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The Euclidean Alternative

• Explicit assumptions, not typically in
  definitional form
• Derivation of Consequences
• Application
• Good Examples Newton Frege Hilbert
  Kolmogorov Minkowski
• Bad examples Woodger, Carnap