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1 History

The test was inspired by a party game known as the "Imitation Game", in which a man and a woman go into separate rooms, and guests try to tell them apart by writing a series of questions and reading the typewritten answers sent back. In this game, both the man and the woman aim to convince the guests that they are the woman.

Turing originally proposed the test in order to replace the emotionally charged and for him meaningless question "Can machines think?" with a more well-defined one.

One interesting part of his proposed test was that the answers in conversation would have to be delivered at controlled intervals and rates. He believed this necessary to prevent the observer drawing a conclusion based on the fact the computer potentially would answer so much faster than the human operator, especially on mathematical questions.

2 Objections and replies

Turing himself suggested several objections which could be made the test. Below are some of the objections and replies from the article in which Turing first proposed the test.

1. Theological Objection: This states that thinking is a function of man's immortal soul and therefore a machine could not think. Turing replies by saying that he sees no reason why it would not be possible for God to grant a computer a soul if he so wished.
2. Mathematical Objections: This objection uses mathematical theorems, such as Gödel's incompleteness theorem, to show that there are limits to what questions a computer system based on logic can answer. Turing suggests that humans are too often wrong themselves and pleased at the fallability of a machine.
3. Argument From Consciousness: This argument, suggested by Professor Jefferson Lister states, "not until a machine can write a sonnet or compose a concerto because of thoughts and emotions felt, and not by the chance fall of symbols, could we agree that machine equals brain". Turing replies by saying that we have no way of knowing that any individual other than ourselves experiences emotions, and that therefore we should accept the test.
4. Lady Lovelace Objection: One of the most famous objections, it states that computers are incapable of originality. Turing replies that computers could still surprise humans, in particular where the consequences of different facts are not immediately recognizable.
5. Informality of Behaviour:This argument states that any system governed by laws will be predictable and therefore not truly intelligent. Turing replies by stating that this is confusing laws of behaviour with general rules of conduct.
6. Extra-sensory perception: Turing seems to suggest that there is evidence for extra-sensory perception. However he feels that conditions could be created in which this would not affect the test and so may be disregarded.

3 Discussion of relevance

It has been argued that the Turing test can not serve as a valid definition of machine intelligence or "machine thinking" for at least three reasons:

1. A machine passing the Turing test may be able to simulate human conversational behavior, but this may be much weaker than true intelligence. The machine might just follow some cleverly devised rules. (A common rebuttal in the AI community has been to ask: how do we know humans don't just follow some cleverly devised rules?) Two famous examples of this line of argument against the turing test are Jon Searles' Chinese room argument and Ned Blocks' Blockhead argument.
2. A machine may very well be intelligent without being able to chat like a human.
3. Many humans that we'd probably want to consider intelligent might fail this test (e.g. the young or the illiterate). (On the other hand, the intelligence of fellow humans is almost always tested exclusively based on their utterances.)

Another potential problem, related to the first objection above, is that even if the Turing test is a good operational definition of intelligence, it may not indicate that the machine has consciousness, or that it has intentionality. Perhaps intelligence and consciousness, for example, are such that neither one necessarily implies the other. In that case, the Turing test might fail to capture one of the key differences between intelligent machines and intelligent people. Of course, machines passing the test would most likely vehemently disagree.