A leading expert in artificial intelligence has predicted that it is only a matter of time before computers will be able to interact on a personal level and talk problems over just like another human.

"In 40 years' time you'll be used to using conscious computers and you wouldn't buy one unless it was conscious," said Professor Igor Aleksander, head of neural systems engineering at Imperial College London.

Addressing the British Association Festival of Science at Cardiff University, he continued: ""It would probably use language and be quite responsive to vision, so you could show it things you're describing.

"The big change is that a conscious computer might answer a problem by saying, `I see what you mean, but I think we should do X, Y or Z'.

"It could conceivably disagree and argue with you. When a computer starts using the word I in that context then we'll know that it's fully conscious."

"At the moment you can buy a piece of software for £25 that enables you to talk to a computer. It doesn't understand anything, but one day it will," he said.

Neural network

How are you today computer?

Professor Aleksander says he has already demonstrated a degree of computer consciousness using a machine called Magnus modelled on the neural network of the human brain.

The aim of the research is to give a computer an understanding of its surroundings, with experimentation is focused in the recall of sensory experience.

For example, the computer is shown a kitchen table and asked to identify if there is a spoon present, and if so, how many.

Magnus has shown that to some extent it can feel the quality of things, such as "redness" or "ballness" when visualising a red ball.

Computing with emotion

The prospect of conscious machines is a mainstay of many science fiction films. Perhaps the most well-known is HAL, the homicidal computer in the film 2001 A Space Odyssey.

Professor Aleksander said the ethical problem of "killing" a conscious computer by switching it off would not arise. The machine would not feel threatened by such action.

"A conscious computer would be so different from a conscious living thing," said the professor.