In 1935 Turing described an abstract computing machine consisting of a limitless memory and a scanner that moves back and forth through the memory, symbol by symbol, reading what it finds and writing further symbols. This is Turing’s stored-program concept, and implicit in it is the possibility of the machine operating on, and so modifying or improving, its own program. Turing’s conception is now known simply as the universal Turing machine.
“What we want is a machine that can learn from experience, and the possibility of letting the machine alter its own instructions provides the mechanism for this.”
In 1948 he introduced many of the central concepts of AI in a report entitled “Intelligent Machinery.”
One of Turing’s original ideas was to train a network of artificial neurons to perform specific tasks which was later accomplished by Belmont Farley and Wesley Clark of MIT. They ran the first artificial neural network, although limited by computer memory to no more than 128 neurons. The main concept was to understand how the human brain works at the neural level and, in particular, how people learn and remember.
“What we thought we were doing (and I think we succeeded fairly well) was treating the brain as a Turing machine.”
Turing illustrated his ideas on machine intelligence by reference to chess—a useful source of challenging and clearly defined problems against which proposed methods for problem solving could be tested.
Although Turing experimented with designing chess programs, he had to content himself with theory in the absence of a computer to run his chess program. Later, in 1997, Deep Blue, a chess computer built by IBM, beat the reigning world champion, Garry Kasparov, in a six-game match.
While Turing’s prediction that computers would one day play very good chess came true, his expectation that chess programming would contribute to the understanding of how human beings think did not.
In 1950 Turing sidestepped the traditional debate concerning the definition of intelligence, introducing a practical test for computer intelligence that is now known simply as the Turing test.
The Turing test involves three participants: a computer, a human interrogator, and a human foil. The interrogator attempts to determine, by asking questions of the other two participants, which is the computer. All communication is via keyboard and display screen.
The interrogator may ask questions as penetrating and wide-ranging as he or she likes, and the computer is permitted to do everything possible to force a wrong identification.
A number of different people play the roles of interrogator and foil, and, if a sufficient proportion of the interrogators are unable to distinguish the computer from the human being, then (according to proponents of Turing’s test) the computer is considered an intelligent, thinking entity.
However, no AI program has come close to passing an undiluted Turing test.
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