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AI and the future: the Turing Machine

29 Sep 2023 6 minute read
Alan Turing. by avaragado is licensed under CC BY-ND 2.0.

Martyn Rhys Vaughan

This week we move on to one of the greatest minds of the Twentieth Century, namely Alan Turing.

Turing was a genuine polymath, solving problems in biology as well as pure mathematics and basically creating the discipline of Computer Science.

The great German mathematician, David Hilbert, had in 1928 formulated what came to be known as “The Decision Problem”, which became better known as “The Halting Problem.” This sought to establish whether there were objective criteria for deciding whether a mathematical problem was capable of being solved.

The answer came in a paper from Turing in 1936. It is not necessary to go into details of Turing’s solution, which are extremely abstract, but he envisaged a theoretical machine, now known as a “Turing Machine”, that could both read and alter symbols on an infinitely long tape. The tape is made up of cells, each of which contains a symbol.

The machine operates on a series of rules which completely describe what the machine does, based on its current state and what the cell it is reading contains. Depending on what it finds, the machine can either, after a finite number of operations on the tape, reach a final state in which it either outputs an answer and stops, or, it become trapped in an infinite loop.

This is equivalent to the question “Given a set of axioms is there a mechanical process that can always discover whether a given statement is true?”

One of the many interesting things about the Turing Machine is that it can model any existing computer in the real world. A specialised form of the machine, known as a Universal Turing Machine, can precisely do that.

The American John von Neumann (another polymath) built on the new discipline of computing science to propose the real-world architecture which was the foundation of all computers that followed. These two men therefore created the modern computer, which has gone on to be used to develop Artificial Intelligence.

Machine intelligence

Turing was also interested in the philosophical issue of intelligence, specifically, machine intelligence. “Computing Machinery and Intelligence” is a seminal paper written by him on the topic of artificial intelligence. The paper, published in 1950 in the magazine “Mind’, was the first to introduce his concept of what is now known as “The Turing Test”.

Turing’s paper considers the question “Can machines think?” Turing says that since the words “think” and “machine” cannot be clearly defined we should replace them with concepts that can be so defined. To do this one must first find a simple and unambiguous idea to replace the word “think”, second,  it must be defined which “machines” are being considered, and then it will be possible to ask a new question, related to the first. These ideas are utilised in the “Turing Test”.

Rather than trying to determine if a machine is thinking, Turing suggested that it should be determined if the machine can win a game, called the “Imitation Game”. The original Imitation Game is a simple party game involving three players. Player A is a man, player B is a woman and player C (who plays the role of the interrogator) can be of either sex.

In the Imitation Game, player C is unable to see either player A or player B (and knows them only as X and Y), and can communicate with them only through written notes or any other form that does not give away any details about their gender.

By asking questions of player A and player B, player C tries to determine which of the two is the man and which is the woman. Player A’s role is to trick the interrogator into making the wrong decision, while player B attempts to assist the interrogator in making the right one.

Turing proposed a variation of this game, involving a computer: ‘”What will happen when a machine takes the part of A 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?”

So the modified game becomes one that involves three participants in isolated rooms: a computer (which is being tested), a human, and a (human) judge. The human judge can converse with both the human and the computer by typing into a terminal.

Both the computer and human try to convince the judge that they are the human. If the judge cannot consistently tell which is which, then the computer wins the game.

This test can be boiled down to: “If a hidden computer can convince a human by a series of questions and answers that it is human, then it can be said to think.”

The Turing Test has been attempted many times, with varied results. But over time, computers have become ever more successful, and is has been claimed that ChatGPT has passed the Turing Test.

Turing’s own views can be illustrated by a few quotes:

On the Turing Test:  “We can only see a short distance ahead, but we can see plenty there that needs to be done. I believe that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted.”

On the future of computing machines: “It seems probable that once the machine thinking method had started, it would not take long to outstrip our feeble powers… They would be able to converse with each other to sharpen their wits. At some stage therefore, we should have to expect the machines to take control.”

Thus Turing was unambiguous in his view that the future of thought lies with the machine.

Martyn is the author of six SciFi books published by Cambria Publishing. These can be viewed HERE or as Kindle eBooks on Amazon.

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