Every few years, parapsychologists announce the breakthrough they have all been waiting for - proof that psychic phenomena really exist. And then, over the next few years, they find they cannot reproduce the results.
The situation has been thus since Victorian scientists first tried to inject science into the seance room. There are always those - usually physicists and psychologists - who have wanted to use scientific methods to investigate psychic phenomena, the human ability to communicate with somebody else or their environment using channels not accepted by orthodox science, such as clairvoyance, telepathy, precognition and psychokinesis.
Since Darwin took away the idea that man was created by God, there has been a certain appeal to the notion that there is something inexplicable about human consciousness that has kept us centre-stage. It is a contradictory stance - the desire to retain the mystery yet seek its explanation through science. Nevertheless, in this century some scientists have found success with extremely complex parapsychology experiments carried out under controlled conditions. But, again, problems have arisen in attempts to reproduce the phenomena in more than one laboratory.
As well as scientific exploration, there has always been the popular fascination with parapsychology, encouraged by a media that knows stories about psychic phenomena attract an audience.
The challenge for traditional science is to demonstrate that the world is, in fact, a far more complex and interesting place than we could have ever imagined and to encourage in people a sense of wonder about science rather than the paranormal.
Science cannot prove something does not exist: it can only ask if there is enough evidence to show that it does exist. There is always just enough evidence to convince the people who want to believe, but not enough to convince the sceptics. It is an ambiguous database that is brilliantly borderline. I wonder what would happen to the field if someone proved telepathy was the product of some weird electromagnetic wave and we could fully understand its mechanism. Perhaps the field would disappear overnight because the mystery would have gone.
Richard Wiseman is a reader in psychology at the University of Hertfordshire.
Interview by Steve Farrar