chips, or be made of brain cells, beer cans, water
pipes, or anything else at all, as long as it carries
out the same operations. This gives rise to the
idea of the Universal Turing Machine, a machine
that can, in principle, imitate any other Turing
machine. The ‘in principle’ is needed because the
machine may require an unlimited memory store
and unlimited time in which to do its calculations.
Even so, modern computers can be thought of as
universal Turing machines, since many different
‘virtual machines’, such as word processors, web
browsers, or spreadsheets, can be run on the
same physical machine; even PowerPoint has
been shown to be able to simulate any Turing
machine.
Even the slow and cumbersome early comput-
ers inspired comparisons with the human mind.
During the Second World War, the Cambridge
psychologist Kenneth Craik began to develop
the idea that the human mind translates aspects
of the external world into internal representa-
tions and that perception, thought, and other
mental processes consist of manipulating these
representations according to definite rules, as a
machine might do. He died in a car crash at the
age of 31, but these ideas became one of the
dominant paradigms in psychology for the rest
of the century, giving rise to the idea that what
we are conscious of is these internal representa-
tions or mental models – in other words, that the
contents of consciousness are mental representations.
Although computers rapidly became faster, smaller, and more flexible, initial
attempts to create AI depended on a human programmer writing programs that
told the machine what to do using algorithms that processed information accord-
ing to explicitly encoded rules. This is now referred to – usually by its critics – as
GOFAI (pronounced ‘goofy’), or ‘Good Old-Fashioned AI’.
One problem for GOFAI is that human users treat the processed information as
symbolising things in the world, but these symbols are not grounded in the real
world for the computer itself. So for example, a computer might calculate the
stresses and strains on a bridge, but it would not know or care anything about
bridges; it might just as well be computing stock-market fluctuations or the
spread of a deadly virus. Similarly, it might print out plausible replies to typed
questions without having a clue about what it was doing. Because such machines
merely manipulate symbols according to formal rules, this traditional approach is
also called rule-and-symbol AI.
PRoFILe 12.1
Alan Turing (1912–1954)
Born in London and educated at
Cambridge, Alan Turing was an
extraordinarily brilliant mathe-
matician. He is often called the
father of both computer science
and artificial intelligence, partly
because of his famous work
on computable numbers which
led to the idea of the Universal Turing Machine. He also
created the Turing Test, which pits a machine against a
person as a way of finding out whether the machine can
think. Thirty years after the Second World War, Turing
was revealed as the master code-breaker who had broken
the famous Enigma cipher. He also created the first func-
tioning programmed computer, the Colossus, to read the
highest-level German secret codes. He was homosexual,
and was eventually arrested and tried for what was then
illegal behaviour, and forced to take female hormones.
He died in June 1954 of cyanide poisoning, probably by
suicide. He was granted a posthumous Royal pardon in
2013.