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like a duck

posted 29 Feb 2012, 13:33 by John Brown   [ updated 18 Apr 2012, 22:09 ]
Much has been written about the now famous Turing Test (Turing 1950). In one sense Turing's challenge was provocative in pitting the capabilities of an inanimate machine against the only readily agreed example of intelligence (a human). On the other hand, Turing also avoided considerable controversy by merely asking that the machine imitate human intelligence rather than display genuine intelligence. In this seminal paper, Turing did not attempt to provide an explicit definition of intelligence, but he may have pointed to the only sensible definition none-the-less.

Turing proposed an 'imitation game' in which a human interrogator must determine the gender of two unseen respondents, a man and a woman. The interrogator may pose any number of questions to the respondents but must rely entirely on typewritten responses. The objective of the male respondent is to cause the interrogator to err while that of the female respondent is to assist the interrogator. Turing then asks what will happen when a machine takes the part of the male respondent 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? 

Turing chose to use the thinking ability of a human interrogator to discriminate a successful imitation of thinking. This is a curiously circular approach, where thinking is being employed to recognize thinking. 

From the perspective of natural selection, it is tremendously important for an agent (an organism that can act on the environment) to be able to rapidly identify another agent in the environment. A nearby agent immediately presents four important alternatives, the famous four F's; to fight, feed, flee or procreate. These four are simply make or break issues as far as the gene's replication success is concerned. The presence of another agent in the environment introduces an entirely different level of cognitive challenge. A piece of fruit or a cliff are passive aspects of the environment where time for decision and action is plentiful. Two agents meeting in the environment are under severe time pressure to select between the four alternatives and act accordingly. Pascal Boyer describes humans as having hyper-active agent detection (Boyer 2001). Brain's have evolved particular excellence in identifying and evaluating other agents. Turing's choice would appear to be well justified in this light.

Turing required that the interrogator and respondents employ human language as the medium of the intelligence contest (rather than say pattern matching or mathematics).

Human language skills are striking in contrast to other species and provide important insight into the human brain. Sydney Lamb investigates the nature of human language with a keen recognition for it's dependence on the brain structures involved (Lamb 1999). Spoken language developed thousands of years before written texts and children learn to speak prior to learning to read and write. Hence, speech is more important than writing to learn about the brain, and it is clear that brains do not store and process the symbols that have later been introduced to write with. There are many common structures and mechanisms across the diversity of human language. Lamb concludes that the linguistic system in human brains is not a single system but an interconnected group of different systems.

While human language was the Turing's medium of choice, the contest itself was deception.

Again from the perspective of natural selection, Dawkins explains that some animals cause other animals to perform actions which are against their best interests (Dawkins 1997, 1999) and that these manipulations result in a arms race of adaptation and counter-adaptation. For example, cuckoo birds routinely place eggs into the nest of robins to obtain free child care, an in doing so have set off an arms race of mimicry and detection between the two species. Dawkins goes so far as to say that "...most animal signals are best seen as neither informative or deceptive, but rather as manipulative." Inanimate objects can only be moved by brute force but other animals can be manipulated by more subtle and efficient means. According to Darwin, manipulation is the intent, and language the medium. Again Turing's choice would appear well founded.

Turing's challenge focuses directly on two of the most highly evolved aspects of human intelligence; language and deception. It is a keen test indeed.

When I see a bird that walks like a duck and swims like a duck 
and quacks like a duck, I call that bird a duck.”  
James Whitcomb Riley.

Were a machine to pass the Turing Test, then people may or may not accept that the machine can think. However, evolution has clearly favored those that have given agents the benefit of the doubt, and acted accordingly. This, in fact, was the whole point.


Boyer,P. (2001), Religion Explained: The Evolutionary Origins of Religious Thought. Basic Books 
Dawkins, R. (1987), The Selfish Gene. Oxford University Press. 
Dawkins,R. (1999), The Extended Phenotype. Oxford University Press. 
Lamb,S.M (1999), Pathways of the Brain: The Neurocognitive Basis of Language. John Benjamins Publishing Co.
Turing, A.M. (1950) Computing Machinery and Intelligence. Mind 49: 433-460.