Alan Turing and the Birth of Machine Intelligence

March 15, 2018
Sohrob Kazerounian
Distinguished AI Researcher
Alan Turing and the Birth of Machine Intelligence

To truly understand the history of AI, it is crucial to delve into the formalization of computation and its significance in determining what it means for something to compute. The catalyst for formalization can be traced back to a thought-provoking inquiry by mathematician David Hilbert in 1928.

This inquiry, known as the Entscheidungsproblem or decision problem, posed the question of whether it was feasible to create an algorithm that could determine the validity of any formal statement in first-order logic, providing a definitive "yes" or "no" response.

Alan Turing and the Formalization of Computation: Revealing the Genius Behind Modern Computing

Nearly a decade later, a brilliant mathematician by the name of Alan Turing shattered Hilbert's aspiration of discovering such an algorithm. In his seminal work from 1937, aptly titled "On Computable Numbers, With an Application to the Entscheidungsproblem," Turing laid the groundwork for the concept of computation. His pioneering paper unveiled a theoretical machine that would later become the blueprint for the sophisticated digital computers that exist today. It is worth noting that this significant contribution to the field was independent of a proof put forth by Alonzo Church the year before.

“We may compare a man in the process of computing a real number to a machine which is only capable of a finite number of conditions…”   – Alan Turing

The Birth of the Turing Machine (TM)

To define his automatic machine, known today as a Turing Machine (TM), Turing drew inspiration from the process undertaken by a computer, which in his sense of the word referred to a human who computes. Deconstructing the human procedure to its constituent elements, Turing wrote:

We suppose that the computation is carried out on a tape; but we avoid introducing the ‘state of mind’ by considering a more physical and definitive counterpart of it. It is always possible for the computer to break off from his work, to go away and forget all about it, and later to come back and go on with it.
If he does this he must leave a note of instructions (written in some standard form) explaining how the work is to be continued. This note is the counterpart of the ‘state of mind.’ We will suppose that the computer works in such a desultory manner that he never does more than one step at a sitting.

Components of a Turing Machine

Turing's "a-machine" was characterized by its utilization of an infinite tape for writing symbols, a read head for interpreting symbols from the tape, a register for keeping track of the machine's state, and a state table for guiding its next actions, such as symbol manipulation, tape movement, etc. Based solely on these components, Turing posited that any effectively calculable task could be computed by a Turing Machine (TM). Remarkably, he demonstrated the possibility of constructing a Universal Turing Machine (UTM) capable of simulating any other TM by providing it with a complete TM specification as input.

This UTM, essentially a stored-program computer, served as a significant inspiration for John von Neumann in devising the first modern digital computers, known today as the von Neumann architecture.

Empowered with a formalism that defined computing machines, Turing delved into the concept of machine intelligence. In his influential 1950 article "Computing Machinery and Intelligence," he introduced his renowned test of machine intelligence, now recognized as the Turing test. Contemplating the adequacy of employing ordinary definitions of "machine" and "intelligence," he began to explore the meaning of machine cognition in greater depth.

I propose to consider the question, "Can machines think?" This should begin with definitions of the meaning of the terms ‘machine’ and ‘think.’ The definitions might be framed so as to reflect so far as possible the normal use of the words, but this attitude is dangerous.
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. But this is absurd.

Turing's Test of Machine Intelligence

Turing proposed a test inspired by the imitation game. In this test, an interrogator's objective is to distinguish between two players, one female and the other hidden from sight. Both players attempt to deceive the interrogator through written answers.

In Turing's version, the male player is replaced by a machine striving to fool the interrogator into believing it is female. While the game's concept involved the interrogator identifying the hidden female player, the fundamental form of the Turing test revolves around differentiating a machine's performance from that of a human, whether in a game like chess or during open conversation.

Turing also established specific criteria for the machines considered in the test.

The question which we put in [Section 1] will not be quite definite until we have specified what we mean by the word ‘machine.’ We are the more ready to do so in view of the fact that the present interest in ‘thinking machines’ has been aroused by a particular kind of machine, usually called an ‘electronic computer’ or ‘digital computer.’ Following this suggestion, we only permit digital computers to take part in our game.

Turing's Personal Beliefs

Having restricted the types of machine to digital computers, and defining the measure by which they are be judged, Turing provides his own feelings on the original question, before responding to other objections to it:

It will simplify matters for the reader if I explain first my own beliefs in the matter. The original question ‘Can machines think?’ I believe to be too meaningless to deserve discussion. Nevertheless, 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.
I believe further that no useful purpose is served by concealing these beliefs. The popular view that scientists proceed inexorably from well-established fact to well-established fact, never being influenced by any improved conjecture, is quite mistaken.

Turing's Dismissal of the Question

Surprisingly, despite the extensive discussions and disagreements surrounding the Turing test, Turing himself disregarded its significance. While he acknowledged that, by the end of the 20th century, people might naturally use the term "thinking" to describe machines, he remained indifferent to this possibility. For Turing, whether a machine was labeled as "thinking" or "intelligent" held no relevance.

The only ascertainable measure was the machine's ability to mimic human behavior, gauged by its capacity to convincingly deceive an observer into believing it was truly human.

Despite the extensive commentary and disagreement surrounding the Turing test, Turing himself regarded the question as meaningless. While he acknowledged the possibility of "thinking" becoming a natural term applied to machines in the future, he remained relatively indifferent towards this prospect.

For Turing, the classification of a machine as "thinking" or "intelligent" held little significance. The crucial aspect was the machine's ability to mimic human behavior, ultimately determined by its success in deceiving observers into believing it was human.