Philosophy and Cogsci

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Philosophy and Cogsci

• The Turing Test
• Joe Lau

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Alan Turing (1912-1954)

• Famous British mathematician / logician
• Mathematical theory of computation.
• Helped cracked the German U-boat Enigma code in
  WWII.
• A homosexual, arrested in 1952.
• Committed suicide.

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More information

• More on Turings life
• Turings biographer Andrew Hodges
  http//www.turing.com/turing/Turing.html
• Computation theory
• Book Boolos and Jeffreys Computability and
  Logic
• Article in Stanford Encyclopaedia of Philosophy
  (web)

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Topic

• 1950 paper in Mind Computing Machinery and
  Intelligence
• Introduced computers to philosophy
• Argued for the plausibility of thinking machines
• Proposed Turing test often cited as criterion
  of success for AI.

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Turings Proposal

• The question Can machines think? is too vague.
• What are machines?
• What is thinking?
• Replace by
• Can computers pass the imitation game?

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The Imitation Game

• Judge talks to a man and woman through teletype
  and has to decide which is which.
• Turing What if the man is replaced by a
  computer?
• Passing the test the judge cannot do better
  than guessing.

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What is the test for?

• What is the purpose?
• One proposal provides a (behavioral) definition
  of thinking
• Probably not
• Turing thought that the question of whether
  machines can think is too meaningless to deserve
  discussion.

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A bad definition anyway

• Definition X ABC
• In a correct definition, ABC are the necessary
  and sufficient conditions for X.
• Passing the test is neither necessary nor
  sufficient for thinking.

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Passing not necessary

• Things that think, but which fail the test
• Systems that can think but cannot communicate
  with a language, or too shy or paranoid to do so.
• The judge might be a computer expert who can
  detect subtle hints.

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Turing on clever judges

• Turing recognized an objection similar to the
  last point.
• He said that "we need not be troubled" as long as
  there are machines that can pass the test.
• So he did concede that passing the test is not
  necessary for being able to think.

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Also not sufficient

• Things that cannot think, but pass the test
• Blockhead a stupid machine that stores all
  possible conversations within some limited
  duration.
• Blockhead is logically possible, but not
  practically possible.

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Blockhead

• Ned Block The Mind as the Software of the Brain

All possible opening lines from the judge
All possible replies
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Proposal

• The test is a practical sufficiency test for
  intelligent thinking.
• Often taken as a practical goal for AI.
• Allows for thinking computers that fail the test.

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Other issues

• Problems with judges
• Who can be a judge? What if a computer passes the
  test because of a stupid judge?

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Real tests

• The Loeber Prize