Thursday 2/1

Thursday 2/1

The Turing Test

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Today we revisited the two threads--one philosophical leading to machine functionalism; the other mathematical leading to computationalism, whereby thought itself is merely the matter of the rule-governed manipulation of strings of 'symbols'--and discussed how they neatly mesh to make the optimistic case for 1) the possibility of Artificial Intelligence and 2) the possibility of understanding the Mind in light of Dretske's Dictum.

Of course, the notion that intelligence can ultimately be boiled down to mechanical or computational processes raises two crucial questions:

What is intelligence?

and,

What is mechanism?

We began today with the puzzle of intelligence.

In his unusually accessible essay “Computing Machinery and Intelligence”, Turing suggests that the question of whether a machine is intelligent is hopelessly ill-formed and perhaps unanswerable in that form. After all, there are many things we mean by 'intelligent', and it is not clear what all of them have to do with one another. Turing proposed that we replace the question of machine intelligence with an imitation game in which an interlocutor interrogates a machine and a person by teletype (today: chatroom) to determine which is which. This is a strictly behavioral test. If the machine can fool the interlocutor better than average number of times, then the machine is behaviorally indistinguishable from a person insofar as 'verbal' behavior is concerned.

Turing's biography, you may recall, is both fascinating and historically eventful, including as it does Bletchley Park, World War II, the German U-Boat "wolf-packs", and the Naval Enigma Cypher machine.

Andrew Hodges' "Alan Turing: The Enigma" is an excellent source for more material on this important bit of history.

To be sure, Turing's importance only begins with his contributions towards cracking naval enigma. For on the one hand he helped us grapple with the thorny question of intelligence, while on the other hand he, more than anyone, provided the theoretical foundation upon which the modern computer is built.

Turing's key insight on the puzzle of intelligence, which we will have many opportunities to critically examine, can be simply put as the proposition that

The perfect imitation of intelligence is intelligence.

Or, at least, it is enough to satisfy any questions about 'intelligence' we could meaningfully ask.

It bears noting that psychometrics, the study of the measure of psychological phenomena, has thus far born out his suspician: We really have no idea what intelligence is.

Suppose, though, that we reject Turing's dismissal of the intelligence question. If we think that the question of intelligence is meaningful apart from the Turing Test, then we must ask about the relationship between a machine's passing the test and whether the machine is intelligent.

It would be a mistake to argue that passing the Turing Test is both necessary and sufficient for intelligence. That is, it would be a mistake to assert that

1. X passes the Turing Test if, and only if, X is intelligent.

(1) is clearly false. Consider that (1) expresses the conjunction of two propositions:

2. If X passes the Turing Test, then X is intelligent. (The Turing Test is a sufficient condition on, or suffices for, intelligence.)

3. If X is intelligent, then X passes the Turing Test. (The Turing Test is a necessary condition on, or necessary for, intelligence.)

(3), though, is false. If the question of intelligence is at all meaningful, one can be intelligent without passing the Turing Test. There are lots of reasons why an intelligent being might lose the Turing Test. Inability to type would be one reason; speaking another language would be another.

The interesting question, from our standpoint, is whether passing the Turing Test is a sufficient condition on intelligence--i.e., is (2) true?

There are roughly two skeptical responses to the assertion (2) that passing the Turing Test suffices for intelligence: The Turing Test is too strong a condition on intelligence, or the Turing Test is too weak a condition on intelligence.

The Turing Test is Too Strong (aka The Problem of False Negatives).

First, one might argue, as researchers in computer science and robotics sometimes do, that the Turing Test is simply too strong a condition on intelligence because intelligence is not always expressed verbally. Witness the Mars rovers Spirit and Opportunity. The rovers would fail the Turing Test miserably, yet it can be argued that they have behavioral capacities on a par with insect-level intelligence. Intelligence has evolved, and so too with our machines. It may be a very long time before we can create machines that can reliably pass the Turing Test, yet we should not for that reason refuse to see the fantastically complicated and sophisticated behavioral repertoire of their predecessors as anything but intelligence.

In short, this objection holds that the Turing Test is too strong in the sense that it ignores as intelligent many things that should rightfully be considered intelligent. Perhaps dog and dolphin-lovers will concur.

The Turing Test is Too Weak (aka The Problem of False Positives).

A much more common objection to the Turing Test is that it is simply too weak. According to this objection, the Turing Test could in principle result in false positives: things that pass the test but ought not be considered intelligent. The most common source of these objections has been the philosophical community, and many of these bear careful scrutiny, as we shall see.

Whether the Turing Test is too strong, too weak, or, as an android Goldilocks might wish, just right, it is clear that Turing has done much to help us sharpen the debate over the possibility of artificial intelligence.

Here are some useful links for further reading about Alan Turing and the Turing Test: