Though London-born, he did his most significant work at the Massachusetts Institute of Technology in Cambridge, Massachusetts, and was among the organisers of the Dartmouth Conference of 1956 at Dartmouth College, New Hampshire. The first public meeting on artificial intelligence, it introduced the term into general use.

The idea of artificial intelligence, that a mechanical ''brain'' might some day be capable of ''learning'' from its experiences and evolving into a superior form, has been regarded by some as the Holy Grail of computer science, though in Hollywood it is more often portrayed as its nemesis. It was only with the invention of the programmable digital computer in the 1940s that it became practicable to postulate how such a machine might be designed, and the ways in which its intelligence could be assessed.

The Turing test is based on the premise that, if a machine can hold a conversation with a person (using a keyboard and screen) and the person is unable to tell whether he or she is conversing with a person or a machine, then the computer can be regarded as ''thinking''.

Alan Turing, who died in 1954, believed machines would be powerful enough to pass the test by 2000. Current predictions put that date at somewhere in the third decade of this century.

Computers are now powerful enough to fool some of the people some of the time, and have been able to beat humans at chess for several years. Their ability to do this is based upon speed and number-crunching ability: the computers of today are no more intelligent than Colossus, at Bletchley Park, the British code-breaking organisation in World War II.

Selfridge's early work in the field of pattern recognition was detailed in his 1959 paper Pandemonium: a Paradigm for Learning, a classic in the artificial intelligence field. Recognising that previous attempts to model human thought had been less than successful, he introduced ''Pandemonium'' as a learning model that was able to improve itself over time in its task of recognising dots and dashes of Morse code. The paper also introduced the notion of parallel processing, the machine being able to process more than one piece of information at the same time a concept fundamental to human thought patterns.

Pandemonium proposes specialised ''demons'' with single tasks, which assess the data in a manner that improves with time. Selfridge could demonstrate the distinguishing of dots and dashes in Morse code and recognise 10 hand-drawn characters. It is, in fact, an early description of a neural network. Pandemonium proved to be such a successful model of human pattern recognition that it has been adopted and adapted for use in cognitive psychology.

Some of Selfridge's ideas were summarised in The Computer as a Communications Device (1968), a paper by J.C.R. Licklider and Robert W.Taylor in the journal Science and Technology. Honouring Selfridge, the authors referred to an Oliver (online interactive vicarious expediter and responder) an early description of a computerised PA. Selfridge, a grandson of Harry Gordon Selfridge, the American founder of London's Selfridges department store, was educated at Malvern College, Worcestershire.

At the outbreak of World War II, the family emigrated to the US and Oliver went to Middlesex school in Concord, Massachusetts.

He graduated with a bachelor's degree in mathematics from MIT in 1945. After service in the navy, he returned there as a graduate student, and studied under the founder of the science of cybernetics, Norbert Wiener.

Much of Selfridge's career was spent at MIT's Lincoln laboratory where, as associate director of Project MAC in the 1960s, he worked on multi-access computing. He served on the advisory board of the US National Security Agency, where he chaired the data-processing panel. Along with scholarly papers and technical books, he wrote several books for children.

His marriages to his first wife, Allison, and second wife, Katherine, ended in divorce.

He is survived by his partner, Edwina Rissland, their daughter Olivia, his children from his first marriage, Peter, Mallory and Caroline, his sister, Jennifer, and six grandchildren. Andrew Spark