The Mind Machine has been travelling the UK since March 1999, gathering data to see if people really can put mind over matter.

The Mind Machine works by asking people to try and influence the toss of a coin, seen on a computer screen. In a logical world, people would correctly predict the result of the toss 50% of the time.

But if mind power can influence the computer into giving the result a person wants, then they would be right more than 50% of the time. Some small scale experiments suggest that people who claim to be psychic can do this.

But the Mind Machine's inventor, psychologist Dr Richard Wiseman from Hertfordshire University, says: "Some people argue that if this sort of ability does actually exist, it will be very small.

Tower of psychic power: the Mind Machine

"So the only way to find out if it is there is to get lots and lots of people guessing. We hope to have 250,000 people by the end of the 1999."

The Mind Machine programme works through a touch-sensitive screen. It first asks people to answer four quick questions, including whether they are male or female and a sceptic or believer.

Everyone is then given four attempts to psychically influence a computerised coin toss. For each attempt, people are first asked to call either heads or tails. The computer then uses a pseudo-random number generator to decide the outcome of the toss.

Dr Wiseman says that 16,500 people have tried the mind machine so far. He told BBC News Online: "We are not looking at any of the results until next year. If we did and saw a strong trend one way or the other, we might be tempted to stop the test."

"So far we have had more men than women and more believers than sceptics, so at the BA Festival of Science we are on the lookout for female sceptics."

In the UK about 55% of people believe in some kind of psychic ability.