On Defining the Intelligence of Behaviour and Machines

Despite its merits the Turing test does not analyse intelligence in a practical way. The "intelligence" of psychologists is l itt le better but consideration of psychological and neurological ideal experiments suggests that intelligence is judged on the basis of the decision-making in the chain ' input-decideoutput'. We cannot separate any specific behaviour syndrome as 'intelligence'-display. Studying 'intellectual tasks' instead of 'intelligence' is l i t t le help since the criteria for identifying and assessing these are either anthropocentrically subjective or based on 'intelligence' itself. Intelligence is best seen as measuring the performance of the highest task selection and control mechanism in a machine. We cannot however escape the need to specify aims. 279 While the Turing test for supposedly intelligent machines has served a definite purpose for by setting an easily comprehended goal it has encouraged research in artificial intelligence the test does have many drawbacks. The two most serious of these are that it offers no information as to what we are to regard as reasonable human-like reactions, and that it does not offer any clue to a step-by-step approach to the creation of an artificially intelligent machine. Turing's proposal, it wil l be recalled, was that instead of vague talk about computers "thinking" or being "intelligent" we substitute discussion of the level of performance achieved by computers in one specific activity. The activity concerned is simply that of responding humanly to our interrogation. If a person is presented with two terminals, one linked to a computer and the other to a human respondent then the computer wi l l have "passed" the test if that person is unable to distinguish which terminal has which linkage. That the Turing test is not sufficiently closely defined is clear if we consider various devious or even "dishonest" ways of satisfying it. We might, for example, construct a machine which gave the human being who was interacting with it the impression that conversation would only be continued on subjects acceptable to the machine and which then steered the conversation in such a way that the initiative always remained with the quite trivially pre-programmed machine. We can all think of individuals who behave in just this way and we do not necessarily regard this behaviour as showing lack of intelligence; prima donna-like behaviour is likely to increase rather than diminish our conviction that we are dealing with a real human being. But do we want prima donna computers ? Many other tricks can be devised which will deceive a human observer into thinking that he is dealing with another human being, but insofar as these rely on quirks of human psychology we tend not to want to build them into A. I. machines. Clearly we have a more subtle definition of intelligence in mind and are not interested in such " t r iv ia l " ways of passing the test. The second drawback to Turing's way of setting the desiderata is that it does not provide us with any guidance for discerning the constituent skills which go to make up intelligent behaviour, and the way in which they have to be combined. When faced with the task of constructing a machine we have to 280 Session No. 6 Analysis of Human Behaviour begin somewhere and are bound to ask of any proposed definition of intelligence that it be analysable in such a way that we are presented with a succession of steps which would lead us towards our goal. In the case of the Turing test we are simply referred back to human intelligence and presented with the task of analysing that before we can even begin to plan the task of constructing the machine. These criticisms are not intended to detract from the positive aspects of Turing's suggestion: among these are (i) that it avoids any reference to particular mechanical devices or systems theoretic entities such as feed-back loops, and (ii) that it lays an emphasis on the relationship between intelligence and human-like behaviour. It is this latter relationship which I now wish to explore in more depth. To start the consideration of machine intelligence with a consideration of human intelligence is not to prejudge the issue in favour of the conclusion that machines cannot be intelligent. It is in fact no more objectionable than commencing an examination of how machines can be made to walk by trying to define exactly what we mean by 'walking' in the case of human beings and animals. If the attribution of "intelligence" to machines is to become anything more than a metaphor we must either invent a new and independent meaning for the word "intelligence" or develop (in Carnap's sense "explicate") the existing term so that it loses its anthromorphic connotation and acquires criteria of applicability which can be applied equally well to machines and men. It is this latter approach that I now wish to pursue. Whether this approach can be successful or not is in my view an open question, and is indeed a pragmatic question: although certain terms which are at present applicable only to human subjects could in principle be explicated or adapted so as to apply equally easily to non-human subjects we should find that the consequences of such adaptation were unacceptable in several cases e.g. "virtuous", "sinful", "vertebrate". We shall have to decide whether a definition of "intelligence" which is so adapted as to apply equally well to machines, does so much violence to our existing system of beliefs and necessary truths about intelligence that we would be better to abandon the search. But let us begin, and let us start by examining human intelligence itself. We may distinguish two types of truth about human intelligence. First there are the insights which we as speakers of English enjoy about what necessarily "goes with" intelligence; whether we call these insights necessary truths, rules of logical grammar, attributes of the deep structure of sentences employing the word 'intelligence' or its cognates, or ultimately entrenched truths, these are the insights which lead us to say that someone's utterance betrays unfamiliarity with the notion, rather than showing a deviant theoretical approach. Secondly, there are the empirical findings which we postulate to be related to what has been diagnosed as intelligence. It is the overriding tendency of the scientific approach to use such empirical findings and particularly the theoretical frameworks used to unify them, as a basis for adaptation of the preliminary definitions on which the f irst type of insight is based. This seems the best policy here, and I propose to review some (psychological) findings related to what has been informally described as intelligent behaviour. Psychologists are loath to use the term 'intelligence' except in the very specific context of I. Q. testing, and even in this field it is customary to disclaim any intention of testing general intelligence. The limitations of psychological tests are well known and it is probably enough to recall that I. Q. does not seem a very good parameter for inventiveness, theoretical insight or creativeness. The question is however a vexed one if only because I. Q. does to some extent correlate with ability to express oneself which may lead to more recognition of the abilities of the high I. Q. subjects and because the social and personal factors determining actual performance may lead even high I. Q. subjects to patently 'unintelligent' behaviour. The state of the art in I. Q. testing is therefore that although some progress has been made we st i l l recognise a difference between what is tested and that which we would wholeheartedly call 'intelligence' while, farther, the tests reveal capacities which may or may not be exercised in