The Information (40 page)

They also managed to attract Alan Turing, who published his own manifesto with a provocative opening statement—“I propose to consider the question, ‘Can machines think?’ ”
^♦
—followed by a sly admission that he would do so without even trying to define the terms
machine
and
think
. His idea was to replace the question with a test called the Imitation Game, destined to become famous as the “Turing Test.” In its initial form the Imitation Game involves three people: a man, a woman, and an interrogator. The interrogator sits in a room apart and poses questions (ideally, Turing suggests, by way of a “teleprinter communicating between the two rooms”). The interrogator aims to determine which is the man and which is the woman. One of the two—say, the man—aims
to trick the interrogator, while the other aims to help reveal the truth. “The best strategy for her is probably to give truthful answers,” Turing suggests. “She can add such things as ‘I am the woman, don’t listen to him!’ but it will avail nothing as the man can make similar remarks.”

But what if the question is not which gender but which genus: human or machine?

It is understood that the essence of being human lies in one’s “intellectual capacities”; hence this game of disembodied messages transmitted blindly between rooms. “We do not wish to penalise the machine for its inability to shine in beauty competitions,” says Turing dryly, “nor to penalise a man for losing in a race against an aeroplane.” Nor, for that matter, for slowness in arithmetic. Turing offers up some imagined questions and answers:

Before proceeding further, however, he finds it necessary to explain just what sort of machine he has in mind. “The present interest in ‘thinking machines,’ ” he notes, “has been aroused by a particular kind of machine, usually called an ‘electronic computer’ or ‘digital computer.’ ”
^♦
These devices do the work of human computers, faster and more reliably. Turing spells out, as Shannon had not, the nature and properties of the digital computer. John von Neumann had done this, too, in constructing a successor machine to ENIAC. The digital computer comprises three parts: a “store of information,” corresponding to the human computer’s memory or paper; an “executive unit,” which carries out individual operations; and a “control,” which manages a list of instructions, making sure they are carried out in the right order. These instructions are encoded as numbers. They are sometimes called a “programme,” Turing explains, and constructing such a list may be called “programming.”

The idea is an old one, Turing says, and he cites Charles Babbage,
whom he identifies as Lucasian Professor of Mathematics at Cambridge from 1828 to 1839—once so famous, now almost forgotten. Turing explains that Babbage “had all the essential ideas” and “planned such a machine, called the Analytical Engine, but it was never completed.” It would have used wheels and cards—nothing to do with electricity. The existence (or nonexistence, but at least near existence) of Babbage’s engine allows Turing to rebut a superstition he senses forming in the zeitgeist of 1950. People seem to feel that the magic of digital computers is essentially electrical; meanwhile, the nervous system is also electrical. But Turing is at pains to think of computation in a universal way, which means in an abstract way. He knows it is not about electricity at all:

Turing’s famous computer was a machine made of logic: imaginary tape, arbitrary symbols. It had all the time in the world and unbounded memory, and it could do anything expressible in steps and operations. It could even judge the validity of a proof in the system of
Principia Mathematica
. “In the case that the formula is neither provable nor disprovable such a machine certainly does not behave in a very satisfactory manner, for it continues to work indefinitely without producing any result at all, but this cannot be regarded as very different from the reaction of the mathematicians.”
^♦
So Turing supposed it could play the Imitation Game.

He could not pretend to prove that, of course. He was mainly trying to change the terms of a debate he considered largely fatuous. He offered a few predictions for the half century to come: that computers would have a storage capacity of 10
⁹
bits (he imagined a few very large computers; he did not foresee our future of ubiquitous tiny computing devices with storage many magnitudes greater than that); and that they might
be programmed to play the Imitation Game well enough to fool some interrogators for at least a few minutes (true, as far as it goes).

He did not live to see how apt his prophecy was. In 1952 he was arrested for the crime of homosexuality, tried, convicted, stripped of his security clearance, and subjected by the British authorities to a humiliating, emasculating program of estrogen injections. In 1954 he took his own life.

Until years later, few knew of Turing’s crucial secret work for his country on the Enigma project at Bletchley Park. His ideas of thinking machines did attract attention, on both sides of the Atlantic. Some of the people who found the notion absurd or even frightening appealed to Shannon for his opinion; he stood squarely with Turing. “The idea of a machine thinking is by no means repugnant to all of us,” Shannon told one engineer. “In fact, I find the converse idea, that the human brain may itself be a machine which could be duplicated functionally with inanimate objects, quite attractive.” More useful, anyway, than “hypothecating intangible and unreachable ‘vital forces,’ ‘souls’ and the like.”
^♦

Computer scientists wanted to know what their machines could do. Psychologists wanted to know whether brains are computers—or perhaps whether brains are
merely
computers. At midcentury computer scientists were new; but so, in their way, were psychologists.

Psychology at midcentury had grown moribund. Of all the sciences, it always had the most difficulty in saying what exactly it studied. Originally its object was the soul, as opposed to the body (somatology) and the blood (hematology). “
Psychologie
is a doctrine which searches out man’s
Soul, and the effects of it; this is the part without which a man cannot consist,”
^♦
wrote James de Back in the seventeenth century. Almost by definition, though, the soul was ineffable—hardly a thing to be known. Complicating matters further was the entanglement (in psychology as in no other field) of the observer with the observed. In 1854, when it was still more likely to be called “mental philosophy,” David Brewster lamented that no other department of knowledge had made so little progress as “the science of mind, if it can be called a science.”
^♦

The passing speculators were still looking mainly inward, and the limits of introspection were apparent. Looking for rigor, verifiability, and perhaps even mathematicization, students of the mind veered in radically different directions by the turn of the twentieth century. Sigmund Freud’s path was only one. In the United States, William James constructed a discipline of psychology almost single-handed—professor of the first university courses, author of the first comprehensive textbook—and when he was done, he threw up his hands. His own
Principles of Psychology
, he wrote, was “a loathsome, distended, tumefied, bloated, dropsical mass, testifying to but two facts:
1st
, that there is no such thing as a
science
of psychology, and
2nd
, that WJ is an incapable.”
^♦

In Russia, a new strain of psychology began with a physiologist, Ivan Petrovich Pavlov, known for his Nobel Prize–winning study of digestion, who scorned the word
psychology
and all its associated terminology. James, in his better moods, considered psychology the science of mental life, but for Pavlov there was no mind, only behavior. Mental states, thoughts, emotions, goals, and purpose—all these were intangible, subjective, and out of reach. They bore the taint of religion and superstition. What James had identified as central topics—“the stream of thought,”
“the consciousness of self,” the perception of time and space, imagination, reasoning, and will—had no place in Pavlov’s laboratory. All a scientist could observe was behavior, and this, at least, could be recorded and measured. The behaviorists, particularly John B. Watson in the United States and then, most famously, B. F. Skinner, made a science based on stimulus and response: food pellets, bells, electric shocks; salivation, lever pressing, maze running. Watson said that the whole purpose of psychology was to predict what responses would follow a given stimulus and what stimuli could produce a given behavior. Between stimulus and response lay a black box, known to be composed of sense organs, neural pathways, and motor functions, but fundamentally off limits. In effect, the behaviorists were saying yet again that the soul is ineffable. For a half century, their research program thrived because it produced results about conditioning reflexes and controlling behavior.

Behaviorists said, as the psychologist George Miller put it afterward: “You talk about memory; you talk about anticipation; you talk about your feelings; you talk about all these mentalistic things. That’s moonshine. Show me one, point to one.”
^♦
They could teach pigeons to play ping-pong and rats to run mazes. But by midcentury, frustration had set in. The behaviorists’ purity had become a dogma; their refusal to consider mental states became a cage, and psychologists still wanted to understand what the mind was.

Information theory gave them a way in. Scientists analyzed the processing of information and built machines to do it. The machines had memory. They simulated learning and goal seeking. A behaviorist running a rat through a maze would discuss the association between stimulus and response but would refuse to speculate in any way about the
mind
of the rat; now engineers were building mental models of rats out of a few electrical relays. They were not just prying open the black box; they were making their own. Signals were being transmitted, encoded, stored, and retrieved. Internal models of the external world were created and updated. Psychologists took note. From information theory and cybernetics, they received a set of useful metaphors and even a productive
conceptual framework. Shannon’s rat could be seen not only as a very crude model of the brain but also as a theory of behavior. Suddenly psychologists were free to talk about plans, algorithms, syntactic rules. They could investigate not just how living creatures react to the outside world but how they represent it to themselves.

Shannon’s formulation of information theory seemed to invite researchers to look in a direction that he himself had not intended. He had declared, “The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point.” A psychologist could hardly fail to consider the case where the source of the message is the outside world and the receiver is the mind.

Ears and eyes were to be understood as message channels, so why not test and measure them like microphones and cameras? “New concepts of the nature and measure of information,” wrote Homer Jacobson, a chemist at Hunter College in New York, “have made it possible to specify quantitatively the informational capacity of the human ear,”
^♦
and he proceeded to do so. Then he did the same for the eye, arriving at an estimate four hundred times greater, in bits per second. Many more subtle kinds of experiments were suddenly fair game, some of them directly suggested by Shannon’s work on noise and redundancy. A group in 1951 tested the likelihood that listeners would hear a word correctly when they knew it was one of just a few alternatives, as opposed to many alternatives.
^♦
It seemed obvious but had never been done. Experimenters explored the effect of trying to understand two conversations at once. They began considering how much information an ensemble of items contained—digits or letters or words—and how much could be understood or remembered. In standard experiments, with speech and buzzers and key pressing and foot tapping, the language of stimulus and response began to give way to transmission and reception of information.

For a brief period, researchers discussed the transition explicitly; later it became invisible. Donald Broadbent, an English experimental psychologist exploring issues of attention and short-term memory, wrote of one
experiment in 1958: “The difference between a description of the results in terms of stimulus and response, and a description in information theory terms, becomes most marked.… One could no doubt develop an adequate description of the results in S-R terms … but such a description is clumsy compared to the information theory description.”
^♦
Broadbent founded an applied psychology division at Cambridge University, and a flood of research followed, there and elsewhere, in the general realm of how people handle information: effects of noise on performance; selective attention and filtering of perception; short-term and long-term memory; pattern recognition; problem solving. And where did logic belong? To psychology or to computer science? Surely not just to philosophy.