By Duncan Geere, Wired UK

Are you human or a machine? Prove it, by passing the Turing Test – a test of the ability of a machine to exhibit intelligent behavior.

[partner id="wireduk"] In Alan Turing's 1950 paper, Computing Machinery and Intelligence, the mathematician posed the question: "Can machines think?" But almost immediately he dismissed that question as too "meaningless" to be worthy of discussion, and swapped it for the much-more specific: "Are there imaginable digital computers which would do well in the imitation game?"

Turing's original "imitation game" had nothing to do with artificial intelligence. It was a simple party game with three players – a man, a woman, and a judge of either sex. The judge sits in a room apart from the man and woman, and has to guess which is which from nothing but written communication.

The standard interpretation of the Turing Test today, however, replaces one of the participants with a machine which has to "imitate" intelligence. In this case, the judge has to decide which of the pair is the person, and which is the machine. The computer is successful, and passes the test, if – as Turing puts it – "the interrogator decide[s] wrongly as often when the game is played [with the computer] as he does when the game is played between a man and a woman".

There's a bit of debate over whether the computer and the person are both supposed to try to trick the interrogator into making an incorrect decision or not. In the original imitation game, one of the pair tries to trick the judge while the other does not, meaning that both will be pretending to be the same gender. The common interpretation of the Turing Test today, however, is one of imitation rather than trickery.

One aspect of the test that Turing never made clear is whether the judge should know whether there's a computer in play at all. Serious attempts at passing the test would almost certainly require a double-blind control, where the judge repeats the experiment multiple times – sometimes with a pair of humans, sometimes with the human and the computer, and sometimes with two computers.

While the Turing Test has been lauded for its simplicity and its ability to test across a wide range of intellectual tasks (natural language, reason, knowledge and learning can all be tested), it has also been criticized for a number of reasons. Firstly, the Turing Test doesn't directly test intelligence. Instead it merely tests how much a computer can behave like a human being.

That's an important distinction because some human behavior is unintelligent, and there are plenty of intelligent behaviors that humans don't do. If, for example, a computer solved a mathematical problem that humans don't have the intellectual capability to do, then it wouldn't make it unintelligent but it would make it fail the Turing Test.

A second issue is that simulated intelligence isn't the same thing as real intelligence. A machine that can pass the Turing Test could just be following a large list of mechanical rules. As such, the Turing Test doesn't test whether a machine can genuinely think. The counter-argument to that is that humans could well just be following a large list of mechanical rules, and then you're deep into philosophy of consciousness and intentionality.

Turing, for his part, anticipated this somewhat. He wrote in his original paper: "I do not wish to give the impression that I think there is no mystery about consciousness. There is, for instance, something of a paradox connected with any attempt to localize it. But I do not think these mysteries necessarily need to be solved before we can answer the question with which we are concerned in this paper."

Finally, there's the question of the judge. Because the test is by necessity subjective, a naive interrogator could fail to spot things that an expert would pick out. As a result, most competitions employ computer scientists, philosophers and journalists as judges. It's been pointed out that the tendency of people to ascribe human characteristics to inanimate objects (known as the anthropomorphic fallacy) means that a variety of statues, rocks and religious artifacts have passed the Turing Test consistently throughout history.

Turing believed that a machine capable of passing the test would eventually be developed. He predicted that by the year 2000, machines with approximately 120 megabytes of memory would be able to pass a five-minute test 30 percent of the time. Futurist Ray Kurzweil predicted in 1990 that a machine capable of passing the test would be developed around 2020, but he pushed that date back to 2029 in 2005. In fact, he bet Electronic Frontier Foundation co-founder Mitch Kapor $20,000 (£12.7k) that a computer would pass the Turing test by 2029, specifying the conditions in some detail.

On 23 June 2012, which would have been Turing's 100th birthday, Bletchley Park will host Turing100 – a one-day event during which the Turing Test will be examined in great detail, and more than 150 machines will be subjected to the test by 30 judges. A Turing Education Day, complete with talks from 10 speakers, will follow on 30 June. Tickets are £90 per person.

Image: albertogp123/Flickr

Source: Turing Week at* Wired.co.uk*