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From: dave@cogsci.indiana.edu (David Chalmers)
Newsgroups: comp.ai
Subject: Re: Value of turing test?
Message-ID: <55171@iuvax.cs.indiana.edu>
Date: 24 Aug 90 03:55:14 GMT
References: <14942@csli.Stanford.EDU> <1353@thor.wright.EDU>
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Reply-To: dave@cogsci.indiana.edu (David Chalmers)
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In article <1353@thor.wright.EDU> vdasigi@thor.wright.edu writes:

> "Turing's test can never hope to provide a NECESSARY condition for
> intelligence, but only a SUFFICIENT one."
>
>I believe I quoted him correctly, because I had written it down as
>soon as I saw it. I may have copied it incorrectly, because it appears
>to me that the quote makes more sense if the words NECESSARY and SUFFICIENT
>were interchanged. Comments?

I don't recall the quote in question, but quoted version seems more plausible
than the reverse.  You can argue about the sufficiency clause until the
cows come home -- whether there are operational criteria for intelligence,
and so on -- and this is what tends to be concentrated on.  Indeed,
Turing in his original article says that the important claim is the sufficiency
claim.

Any claim about necessity of TT-passing ability is very dubious, for the simple
reason given by Turing in his 1950 article.

  "May not machines carry out something which ought to be described as thinking
   but which is very different from what a man does?  This objection is a very
   strong one, but at least we can say that nevertheless, if a machine can be
   constructed to play the imitation game satisfactorily, we need not be
   troubled by the objection."

The point is that the TT doesn't test for *intelligence* per se, but for
*human-like intelligence*.  This point was extended in an interesting 
recent article in _Mind_ by R.M. French.  He argues that *no* machine
could pass the Turing Test, unless it had experienced the world exactly as we
had.  The outline of the argument is that no matter how you restrict the class
of questions on the TT, a sufficently assiduous Tester will be able to uncover
differences between a human and an artificial machine by a technique
of "subcognitive probing".  The different subcognitive substrate of such a
machine will manifest itself in non-humanlike answers to certain questions.
Of course, such failure to pass the TT doesn't imply lack of intelligence.

A.M. Turing, "Computing Machinery and Intelligence", Mind, 59:433-460, 1950.

R.M. French, "Subcognition and the Limits of the Turing Test", Mind, 99:53-66,
1990.

--
Dave Chalmers     (dave@cogsci.indiana.edu)      
Concepts and Cognition, Indiana University.

"It is not the least charm of a theory that it is refutable."