An Introduction to Turing's Imitation Game

The Turing test, as outlined in Computing Machinery and Intelligence (1950) was originally to be played by a man and a woman; the aim of the interrogator would be to see if he or she could tell which was the man and which was the woman. Turing developed this argument and applied it to machines:

‘‘‘What will happen when a machine takes the part of A (the man) in this game?’’ Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman? These questions replace our original, ‘‘Can machines think?’’’ (Turing, 1950, p.434)

The imitation game, as Turing envisioned it, should be played as followed:

‘It is played with three people, a man (A), a woman (B), and an interrogator (C) who may be of either sex. The interrogator stays in a room apart from the other two. The object of the game for the interrogator is to determine which of the other two is the man and which is the woman. He knows them by labels X and Y, and at the end of the game he says either ‘‘X is A and Y is B’’ or ‘’X is B and Y is A.’’’ (Turing, 1950, p.433 & 434)

The interrogator may ask X and Y any questions he or she desires, preferably written and via a computer monitor so as not to give any clues away. Therefore, it is on the basis of this information only, that the interrogator can make his or her decision about whether A or B is the machine.

The Purpose of the Turing Test

Theoretically, if the interrogator cannot tell the difference between the computer and the person in this way, then the intelligence of the machine must match that of the person. Turing predicted that in fifty years:

‘It will be possible to programme computers…to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning.’ (Turing, 1950, p.442)

Can Computers Think?

Turing maintained that his imitation game was an acceptable alternative to asking whether or not computers could think. This is because he always maintained that the question ‘Can computers think?’ was not worthy of discussion.

There are several reasons for this. The first is that Turing thought that this question was too ambiguous. (Turing, 1950, p.443) The second reason, which is closely related to the first, is because:

‘If the meaning of the words ‘‘machine’’ and ‘‘think’’ are to be found by examining how they are commonly used it is difficult to escape the conclusion that the meaning and the answer to the question, ‘‘Can machines think?’’ is to be sought in a statistical survey such as a Gallup poll.’ (Turing, 1950, p.443)

Turing refused to answer the question ‘Can computers think?’ because he did not wish to define the words ‘computer’ or ‘machine’ or ‘think’ in the usual sense. Turing aimed to specifically break down the traditional definitions and notions of these words.

Hodges, in his biography of Turing believed that:

‘To avoid philosophical discussion about what ‘mind’ or ‘thought’ or ‘free will’ were supposed to be, he (Turing) favoured the idea of judging a machine’s mental capacity simply by comparing its performance with that of a human being.’ (Hodges, 1985, p.266)

By doing this, all philosophical debate would be neatly side-stepped and the original question answered in a simple, but effective manner. Simply; if a machine communicates like a human, has the knowledge of a human and the intellect of a human then it must be human, at least in all the ways that count.

References:

Hodges, A., 1985, ‘The Enigma of Alan Turing,’ London: Unwin Paperbacks

Turing, A., 1950, ‘Computing Machinery and Intelligence,’ Mind, Vol. LIX, No.236

Alan Turing

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