Pseudomath about the Turing Test: Reply to Padin

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Stevan Harnad

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Oct 27, 1986, 12:23:31 PM10/27/86
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[Until the problem of follow-up articles to mod.ai through Usenet is
straightened out, I'm temporarily responding to mod.ai on net.ai.]

In mod.ai, in Message-ID: <861027072...@ucbvax.Berkeley.EDU>,
under the subject heading THE PSEUDOMATH OF THE TURING TEST,
PA...@FNALB.BITNET writes:

> DEFINE THE SET Q={question1,question2,...}. LETS NOTE THAT
> FOR EACH q IN Q, THERE IS AN INFINITE NUMBER OF RESPONSES (THE
> RESPONSES NEED NOT BE RELEVANT TO THE QUESTION, THEY JUST NEED TO BE
> RESPONSES). IN FACT, WE CAN DEFINE A SET R={EVERY POSSIBLE RESPONSE TO
> ANY QUESTION}, i.e., R={r1,r2,r3,...}.

Do pseudomath and you're likely to generate pseudoproblems. Nevertheless,
this way of formulating it does inadvertently illustrate quite clearly why
the symbolic version of the turing test is inadequate and the robotic version
is to be preferred. The symbolic version is equivalent to the proverbial
monkey's chances of typing Shakespeare by combinatorics. The robotic version
(pending the last word on basic continuity/discontinuity in microphysics) is
then no more or less of a combinatorial problem than Newtonian Mechanics.
[Concerning continuity/discreteness, join the ongoing discussion on the
A/D distinction that's just started up in net/mod.ai.]

> THE EXISTENCE OF ...A FUNCTION T THAT MAPS A QUESTION q TO A SET
> OF RESPONSES RR... FOR ALL QUESTIONS q IS EVIDENCE FOR THE PRESENCE
> OF MIND SINCE T CHOOSES, OUT OF AN INFINITE NUMBER OF RESPONSES,
> THOSE RESPONSES THAT ARE APPROPRIATE TO AN ENTITY WITH A MIND.

Pare off the pseudomath about "choosing among infinities" and you just
get a restatement of the basic intuition behind the turing test: That an
entity has a mind if it acts indistinguishably from an entity with a
mind.

> NOW A PROBLEM [arises]: WHO IS TO DECIDE WHICH SUBSET OF RESPONSES
> INDICATES THE EXISTENCE OF MIND? WHO WILL DECIDE WHICH SET IS
> APPROPRIATE TO INDICATE AN ENTITY OTHER THAN OURSELVES IS OUT THERE
> RESPONDING?

The same one who decides in ongoing, everyday "solutions" to the
other-minds problem. And on exactly the same basis:
indistinguishability of performance.

> [If] WE GET A RESPONSE WHICH APPEARS TO BE RANDOM, IT WOULD SEEM THAT
> THIS WOULD BE SUFFICIENT TO LABEL [the] RESPONDENT A MINDLESS ENTITY.
> HOWEVER, IT IS THE EXACT RESPONSE ONE WOULD EXPECT OF A SCHIZOPHRENIC.

When will this tired prima facie objection (about schizophrenia,
retardation, aphasia, coma, etc.) at last be laid to rest? Damaged
humans inherit the benefit of the doubt from what we know about their
biological origins AND about the success of their normal counterparts in
passing the turing test. Moreover, there is no problem in principle
with subhuman or nonhuman performance -- in practice we turing-test
animals too -- and this too is probably parasitic on our intuitions
about normal human beings (although the evolutionary order was
probably vice versa).

Also, schizophrenics don't just behave randomly; if a candidate just
behaved randomly it would not only justifiably flunk the turing test,
but it would not survive either. (I don't even know what behaving
purely randomly might mean; it seems to me the molecules would never
make it through embryogeny...) On the other hand, which of us doesn't
occasionally behave randomly, and some more often than other?. We can
hardly expect the turing test to provide us with the criteria for extreme
conditions such as brain death if even biologists have problems with that.

All these exotic variants are pseudoproblems and red herrings,
especially when we are nowhere in our progress in developing a system
that can give the normal version of the turing test a run for its money.

> NOW IF WE ARE TO USE OUR JUDGEMENT IN DETERMINING THE PRESENCE OF
> ANOTHER MIND, THEN WE MUST ACCEPT THE POSSIBILITY OF ERROR INHERENT
> IN THE HUMAN DECISION MAKING PROCESS. AT BEST,THEN, THE TURING TEST
> WILL BE ABLE TO GIVE US ONLY A HINT AT THE PRESENCE OF ANOTHER MIND;
> A LEVEL OF PROBABILITY.

What else is new? Even the theories of theoretical physics are only
true with high probability. There is no mathematical proof that our
inferences are entailed with necessity by the data. This is called
"underdetermination" and "inductive risk," and it is endemic to all
empirical inquiry.

But besides that, the turing test has even a second layer of
underdermination that verges on indeterminacy. I have argued that it
has two components: One is the formal theorist's task of developing a
device that can generate all of our performance capacities, i.e.,one
that can pass the Total Turing Test. So far, with only "performance
capacity" having been mentioned, the level of underdetermination is
that of ordinary science (it may have missed some future performance
capacity, or it may fail tomorrow, or it may just happen to accomplish
the same performance in a radically different way, just as the
universe may happen to differ from our best physical theory).

The second component of the turing test, however, is informal, intuitive
and open-ended, and it's the one we usually have in mind when we speak of
the turing test: Will a normal human being be able to tell the candidate
apart from someone with a mind? The argument is that
turing-indistinguishability of (total) performance is the only basis
for making that judgment in any case.

Fallible? Of course that kind of judgment is fallible. Certainly no less
fallible than ordinary scientific inference; and (I argue) no more fallible
than our judgments about other minds. What more can one ask? Apart from the
necessary truths of mathematics, the only other candidate for a nonprobabilistic
certainty is our direct ("incorrigible") awareness of our OWN minds (although
even there the details seem a bit murky...).


Stevan Harnad
{allegra, bellcore, seismo, packard} !princeton!mind!harnad
harnad%mi...@princeton.csnet
(609)-921-7771

and...@ubc-cs.uucp

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Oct 29, 1986, 1:31:18 PM10/29/86
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This endless discussion about the Turing Test makes the
"eliminative materialist" viewpoint very appealing: by the
time we have achieved something that most people today would
call intelligent, we will have done it through disposing of
concepts such as "intelligence", "consciousness", etc.

Perhaps the reason we're having so much trouble defining
a workable Turing Test is that we're essentially trying to
fit a square peg into a round hole, belabouring some point
which has less relevance than we realize. I wonder what old
Alan himself would say about the whole mess.

--Jamie.
...!seismo!ubc-vision!ubc-cs!andrews
"At the sound of the falling tree... it's 9:30"

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