The concept of precognition cannot be dismissed out of hand, experts say.
Experts deny ESP despite evidence
People who claim to see the future have always been regarded with suspicion. And not without cause: all too often "seers" have been revealed to be at best misguided, if not charlatans or just plain mad.
But the opprobrium they face pales beside that endured by scientists brave - or foolish - enough to take the idea of "precognition" seriously.
One of this very rare breed is Dr Daryl Bem, emeritus professor of psychology at Cornell University in the United States. For decades he has combined a distinguished career in conventional research with a parallel role as arguably the most respected scientist prepared to investigate precognition.
Over the years, he has performed many experiments to investigate whether ordinary people can see into the future. And by the standards of conventional science, what he has amassed constitutes compelling evidence that they can.
So why has this not made headlines around the world, and sparked research into how we can all hone our abilities to see the future? The reason is that Dr Bem has met the same fate as that of every other researcher into precognition: his results have been ignored, decried or dismissed as showing nothing more than the existence of ESP: "Error Some Place".
But now he is making headlines, having sparked a storm of controversy by having evidence for precognition accepted by a leading academic journal, the Journal of Personality and Social Psychology, based on experiments involving more than 1,000 people.
Until now, most studies have been twists on a simple theme: predicting the outcome of a coin toss. Random guessing will produce a hit rate of just 50 per cent, while the existence of precognition should boost that somewhat.
If performed, say, 100 times, calling correctly 60 times would represent what scientists call a "statistically significant" hit rate - implying that the chances of doing so well by fluke alone are pretty low.
But that is not the same as saying that precognition must therefore exist, and sceptics have not stinted in offering a host of alternative explanations, ranging from faulty coins to cheating.
Dr Bem has put huge effort into eliminating these other explanations. But what makes his work stand out is that he has gone beyond merely trying to show whether precognition exists. Instead, he has looked at whether the phenomenon has features commonly seen in conventional mental abilities.
For example, it is well-known that stronger stimuli typically produce a stronger response in humans. So Dr Bem got people to guess which of two computer screens was about to show an image. Random guessing would produce a 50:50 hit rate - and that was what the experiment found when the image was of something innocuous, like a wedding. But when he used more shocking images taken from the internet, the hit rate went up. Not by much - it was around 53 per cent - but statistically significant.
Dr Bem has gone further, checking out other characteristics of precognition, such as whether it allows "habituation", in which people respond less strongly to images they have already seen. Taken together, the results suggest precognition does have the features expected of a real mental ability. The overall effect is not huge, but the chances that his results are fluke alone are just one in 100 billion.
So precognition is real; case closed - or at least, it would be if the effect under study were, say, the effectiveness of a new cancer drug.
But for many scientists, precognition is so wacky that they are prepared to give it a much rougher ride than any life-saving therapy. Even before Dr Bem's results appeared, sceptics were lining up to denounce them as crazy. One scientist told TheNew York Times that if any of the results were true "we would have to rethink everything about the nature of the universe".
Some more thoughtful sceptics are insisting the results confirm long-held suspicions about flaws in how scientific evidence is assessed. They are calling for the use of techniques that take account of the inherent plausibility of whatever is being investigated. In the case of precognition, many would deem the inherent plausibility so low that Dr Bem's findings would not come close to making the case.
Other critics have pointed out that the findings have already failed the ultimate test of any genuine effect: replication. Which is true: some scientists have failed to confirm Dr Bem's findings, but others have succeeded.
Just suppose, however, that the sceptics are wrong and precognition really does exist. Would it demand a "rethink of everything"? Not at all; in fact, it would be right in line with one of the cornerstones of our present understanding of the universe: quantum theory. Experiments in the early 1980s showed that our common-sense perceptions of how the universe work are unreliable, and that it is just possible that the past and the future can be temporarily switched round.
At least one Nobel Prize-winning quantum physicist, Prof Sir Tony Leggett of the University of Illinois, believes this means we cannot dismiss the idea of precognition out of hand.
Whether Dr Bem has brought us to the brink of a major discovery remains to be seen. What is clear is that we will never know for sure unless many more scientists show as much courage as Dr Bem and join the quest to find out.
Robert Matthews is Visiting Reader in Science at Aston University, Birmingham, England.