Artificial intelligence and neural networks - The Computing Universe: A Journey through a Revolution - page 265

as he does when the game is played between a man and a woman? These
questions replace our original, “Can machines think?” 3

The Turing Test is often taken as an operational definition of intelligence. In
its modern form, it reads, “A computer passes the test if a human interrogator,
after posing some written questions, cannot tell whether the written responses
come from a person or from a computer.” 4 To pass the test, computers will need
to complete the following tasks: to understand natural language; reason about
the information expressed by words and sentences; and learn from experience.
In 1950, Turing was cautiously optimistic:

I believe that in about fifty years' time it will be possible, to programme
computers, with a storage capacity of about 10 9 , to make them play the
imitation game so well that an average interrogator will not have more than
70 per cent chance of making the right identification after five minutes of
questioning. 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. 5

Turing also gave a famous example of the type of conversation that he imagined
it would be possible to have with a “sonnet-writing” machine in the future. It
would be difficult to learn whether the machine has really understood some-
thing or whether, as he says, it has just “learnt it parrot fashion”: 6

Interrogator: In the first line of your sonnet which reads “Shall I compare
thee to a summer's day”, would not “a spring day” do as well or better?
Witness: It wouldn't scan.
Interrogator: How about “a winter's day”? That would scan all right.
Witness: Yes, but nobody wants to be compared to a winter's day.
Interrogator: Would you say that Mr. Pickwick reminded you of

Christmas?
Witness: In a way.
Interrogator: Yet Christmas is a winter's day, and I do not think Mr.
Pickwick would mind the comparison.
Witness: I don't think you are serious. By a winter's day one means a
typical winter's day, rather than a special one like Christmas. 7

If a computer were capable of such a sophisticated dialog, requiring knowledge
both of literature and Mr. Pickwick as well as of the significance of Christmas,
it would be hard to make a distinction between “real” and artificial thinking.
At present, we still seem to be far from this goal. ELIZA, one of the earliest
“chatbot” programs, simulated an interview with psychotherapist and could be
superficially very convincing (see the short summary of ELIZA at the end of this
chapter, for an example). Its author, Joseph Weizenbaum, chose the psycho-
therapy model precisely because it would not require a significant knowledge
base. ELIZA imitated client-centered therapy, a form of psychotherapy that
tries to increase the patient's insight and self-understanding by restating the
patient's feelings and thoughts.