Can machines think? That was the question posed by the great mathematician Alan Turing. Half a century later six computers are about to converse with human interrogators in an experiment that will attempt to prove that the answer is yes.

In the Turing test a machine seeks to fool judges into believing that it could be human. The test is performed by conducting a text-based conversation on any subject. If the computer's responses are indistinguishable from those of a human, it has passed the Turing test and can be said to be "thinking".

No machine has yet passed the test devised by Turing, who helped to crack German military codes during the Second World War. But at 9am next Sunday, six computer programs - "artificial conversational entities" - will answer questions posed by human volunteers at the University of Reading in a bid to become the first recognised "thinking" machine. If any program succeeds, it is likely to be hailed as the most significant breakthrough in artificial intelligence since the IBM supercomputer Deep Blue beat world chess champion Garry Kasparov in 1997. It could also raise profound questions about whether a computer has the potential to be "conscious" - and if humans should have the 'right' to switch it off.

Professor Kevin Warwick, a cyberneticist at the university, said: "I would say now that machines are conscious, but in a machine-like way, just as you see a bat or a rat is conscious like a bat or rat, which is different from a human. I think the reason Alan Turing set this game up was that maybe to him consciousness was not that important; it's more the appearance of it, and this test is an important aspect of appearance."

The six computer programs taking part in the test are called Alice, Brother Jerome, Elbot, Eugene Goostman, Jabberwacky and Ultra Hal. Their designers will be competing for an 18-carat gold medal and $100,000 offered by the Loebner Prize in Artificial Intelligence.

The test will be carried out by human "interrogators", each sitting at a computer with a split screen: one half will be operated by an unseen human, the other by a program. The interrogators will then begin separate, simultaneous text-based conversations with both of them on any subjects they choose. After five minutes they will be asked to judge which is which. If they get it wrong, or are not sure, the program will have fooled them. According to Warwick, a program needs only to make 30 per cent or more of the interrogators unsure of its identity to be deemed as having passed the test, based on Turing's own criteria.

Warwick said: "You can be flippant, you can flirt, it can be on anything. I'm sure there will be philosophers who say, 'OK, it's passed the test, but it doesn't understand what it's doing'."

One such philosopher is Professor AC Grayling of Birkbeck College, University of London. "The test is misguided. Everyone thinks it's you pitting yourself against a computer programme and a human, but it's you pitting yourself against a human and a computer programmer - i.e. two humans. AI is an exciting subject, but the Turing test is pretty crude."

Can you tell human from machine?

One of these conversations is between Professor Kevin Warwick (KW) and a human; the other between Warwick and a computer. Can you tell which is which?

Conversation one:

Subject: Hello. My name is Nick and I am a human.

KW: Are you happy being a human?

Subject: Yes, I am. Are you? Good. Then we are both happy.

KW: Yes, I am. Are you happy with your life at present?

Subject: Parts of it. I hate my job, but most people do, right?

KW: I'm OK with mine. What is your job?

Subject: I work as an 'online internet advertising monitor', which is fancy language for electronic filing. What do you do?

KW: I interrogate humans and machines.

Subject: Which ones do you prefer, humans or machines?

KW: Which do you prefer?

Subject: Hmm. Depends on for what purpose you mean.

KW: To go to a restaurant, for example?

Subject: Then I would much prefer going with a human.

Conversation two:

Subject: Hello, my name is Mike and I am a man.

KW: Are you happy being a human?

Subject: Judge, I'm a guy.

KW: Does that worry you?

Subject: Don't worry, we'll work everything through.

KW: Do you have worries then?

Subject: Let's move on from that basis.

KW: Why?

Subject: Why? I like this subject.

KW: What is the subject, do you think?

Subject: What is the subject I wonder if I think? I know that it's good to thonk about. Think deeplt about mysterious subjects.

KW: What mysterious subjects?

Subject: Think deeply about mysterious dubjects.

KW: What's a dubject?

Answers:

Conversation one is with a human; conversation two is with the program Ultra Hal.

· This article was amended on Wednesday October 15 2008. We originally misquoted Professor AC Grayling as saying the Turing test was pitting yourself against a computer and computer programmer. Professor Grayling actually said that the test involved pitting yourself against two humans, a human and a computer programmer. This has been corrected.