The Turing Test - 1950

Turing's prophecy that computers would one day think

Turing's 1950 paper in Mind, Computing Machinery and Intelligence, has become one of the most cited in philosophical literature, and heads the list in David Chalmers' bibliography of the philosophy of Artificial Intelligence.

This paper is now available online.

Turing's claim

Turing held that computers would in time be programmed to acquire abilities rivalling human intelligence.

As part of his argument Turing put forward the idea of an 'imitation game', in which a human being and a computer would be interrogated under conditions where the interrogator would not know which was which, the communication being entirely by textual messages. Turing argued that if the interrogator could not distinguish them by questioning, then it would be unreasonable not to call the computer intelligent.

Turing's 'imitation game' is now usually called 'the Turing test' for intelligence.

Turing's 1950 paper has given rise to a large literature, surveyed by:

The central role of computability

The most fundamental statement of Turing's thought in this paper is that the operations of the brain must be computable. The famous Test is secondary. Furthermore, the main point of his paper was to put forward constructive arguments for how machine intelligence should be achieved.

Turing himself argued in this paper that the question of uncomputability in mathematics was not in fact relevant. However the philosopher Michael Polanyi, at Manchester in 1950, disputed Turing's view. In 1961 the Oxford philosopher J. R. Lucas published a paper on the significance of Gödel's theorem which also argued to the contrary. Turing's view was defended by I. J. Good, and then later much elaborated by Douglas Hoftstadter in his 1979 book Gödel, Escher, Bach.

In 1989, Roger Penrose published The Emperor's New Mind which took a completely fresh view of Gödel's theorem, connecting uncomputability with the unknown laws governing quantum physics. His work Shadows of the Mind followed in 1994. A good entry point into this argument is the on-line paper Beyond the Doubting of a Shadow, Penrose's response to criticisms of Shadows of the Mind.



My own summary

My 58-page text on Alan Turing as a philosopher of Mind appeared in 1997. This is Turing, no. 3 of a series The Great Philosophers published by Phoenix (London) and Routledge (New York). This includes substantial extracts from Turing's 1950 paper.

In Alan Turing: the Enigma, I discussed Turing's paper in the light of what seemed to me to be Turing's own doubts about AI --- doubts centred on the serious problem of where to draw a line between thinking and living. The new text has other things to say about the development of Turing's thought, stimulated by Roger Penrose's discussion of computability and consciousness.

More details, extracts, translations, and reviews.
Amazon.com page.

I have written another text for a forthcoming book on the Turing test: this is available on-line as

Alan Turing and the Turing Test.




My cat could think (I think)
but she couldn't pass the test

Other arguments

But there are many other discussions of the role of consciousness and the validity of the 'imitation' argument. Amongst these are:


Wider cultural criticism

Turing's vivid imagery has stimulated many people from beyond the fields of computer science and philosophy.

Arthur C. Clarke was influenced by it, I think, in creating HAL for 2001.

The witty and irreverent style of his paper leaves a vivid picture of Alan Turing's own intelligence, not filtered through academic prose, but as if talking with Cambridge friends.

Or, perhaps, anticipating the techie, Trekky style of net-talk, cocking a snook at the Shakespeare-brandishing culture of official Literature.

You can almost see the : - ) and ; - ) in his symbols.

It is not at all like a stereotyped picture of a mathematician thinking about computers.

A good sense of humour is essential to the computer's replies in Turing's sample conversations.

There is also a definitely camp humour in Turing's paper, reflecting his gay identity, and this has led to...

    		Alan Turing in the bottom row...
    Alan Turing in 1951
    ...of a 1951 group photograph of an
    inter-disciplinary cybernetics meeting...

    acting the cross-legged boy he was at 14...

    Alan Turing in 1926
    ...at Sherborne School in 1926,
    disgracing himself in English.

    A pink herring

    Turing started his paper by describing a game in which a man and a woman compete under these remote-terminal conditions to convince an interrogator that they are the woman.

    This confuses the point Turing wanted to assert, that a computer showing intelligence under these conditions must really be intelligent. After all, the man-woman game, if won by the man, certainly doesn't prove the man is really a woman.

    What he claimed was that with intelligence, as opposed to sex, imitation is as good as the real thing. Turing stressed that the setting of the Turing test, with communication only by symbols, gives a way of separating intelligence from other human characteristics. His irrelevant gender game distracts attention from this point.

    Another problem with this bad analogy is that it has led people into thinking that the Turing test means a computer taking the part of a man who is pretending to be a woman.

    See this psychoanalytic view.

    An unkind textual cut

    A paper in Tekhnema, 3, 37-58, (1996) by the French philosopher Jean Lassègue is a critique of Turing's work by a (post)modern textual scholar. I am all in favour of considering Turing's thought in the context of his life; I have stressed that Turing himself, in his 1950 paper, found it hard to draw the line between thought and life. I agree that nothing in life is irrelevant to the question of AI, and that Turing's choice of the imitation game scenario and other images, must reflect aspects of his personality and personal history.

    However, Lassègue's assertion is much stronger than this: it is that the imitation game 'should be considered as an unconscious and mythical autobiography and not as a philosophical introduction to the main issues of AI.' To support this assertion, he has subjected Turing's texts from childhood letters onwards to literary analysis, drawing far-fetched psychological conclusions from very slight verbal allusions. He has read my work with enormous attention to detail, and given it much praise and prominence for which I am grateful, but unfortunately I cannot agree with his extrapolations.

    To mention one example, where I can definitely make a point of fact, Lassègue has misread a sentence on my page 77. Turing did not suggest in 1933 that his being circumcised 'greatly determined' his being gay. (Circumcision plays a prominent role in Lassègue's theory of the imitation game.)

    On the other hand there is doubt that Turing's very wide-ranging ideas and provocative images have powerful resonances today when computers have come to dominate the means of communication.
    This dramatic production by Jean Peyret, ranging over many issues in science and sexuality, is an example of an artistic response. Turing's democratic and open approach to 'testing' intelligence is one that everyone is invited to share in and respond to.
    Sexuality has been transformed between 1950 and 2000 ... and the computer is playing a part in the process. The Internet is the most erotic medium there has ever been.

    Turing's iconoclastic images have certainly given encouragement to feminist writers...

    ...who want to see technology breaking out of traditional male preserves...
    ...something I agree with very much. Alan Turing was at a great disadvantage in the macho-man engineering world at Manchester, as illustrated on this Scrapbook page.

    Also I agree that to write about Turing's life with any degree of depth and honesty, it is necessary to express an imaginative response which goes beyond quoting and recording. In my book I did this by including poems by Walt Whitman and other allusive references.

    ...I say the Form complete is worthier far,
    The Female equally with the Male I sing...
    The novel The Unwelding that I am writing will show more of my own response to the Turing story. Drama and fiction certainly can express issues which science finds very hard to handle.

    Here is another theatre company with a response to Alan Turing's ideas and images: Reckless Sleepers.

    The Turing story will never be exhausted; there will always be new responses in new words and images. My complaint is only when these are put in terms of definite assertions about Alan Turing for which there is no evidence.