Bem’s experiments suggested that college students could accurately predict random events, like whether a computer will flash a photograph on the left or right side of its screen. However scientists and skeptics soon questioned Bem’s study and methodology. Bem stood by his findings and invited other researchers to repeat his studies.
Replication is of course the hallmark of valid scientific research—if the findings are true and accurate, they should be able to be repeated by others. Otherwise the results may simply be due to normal and expected statistical variations and errors. If other experimenters cannot get the same result using the same techniques, it’s usually a sign that the original study was flawed in one or more ways.
Last year a group of British researchers tried and failed to replicate Bem’s experiments. A team of researchers including Professor Chris French, Stuart Ritchie and Professor Richard Wiseman collaborated to accurately replicate Bem’s final experiment, and found no evidence for precognition. Their results were published in the online journal PLoS ONE.
Now a second group of scientists has also replicated Bem’s experiments, and once again found no evidence for ESP. In an article forthcoming in The Journal of Personality and Social Psychology, researchers Jeff Galak, Robyn LeBoeuf, Leif D. Nelson, and Joseph P. Simmons, the authors explained their procedure: “Across seven experiments (N = 3,289) we replicate the procedure of Experiments 8 and 9 from Bem (2011), which had originally demonstrated retroactive facilitation of recall. We failed to replicate that finding. We further conduct a meta-analysis of all replication attempts of these experiments and find that the average effect size (d = .04) is no different from zero.” In other words there was no evidence at all for ESP. The paper, “Correcting the Past: Failures to Replicate Psi,” is available on the web page of the Social Science Research Network.
Anomalous Results And Replication
So far it’s not looking good for scientific evidence of psychic powers. There are many examples of anomalous studies and experiments that—if true—promise to revolutionize the world but turn out to be wrong. In March 1989 two chemists at the University of Utah, Stanley Pons and Martin Fleischmann, announced that they had discovered a technique for creating cold fusion, a potentially limitless source of free energy. Pons and Fleischmann insisted that their research was valid, though in the past quarter-century no one has reproduced their findings; Fleischmann died last month never having been vindicated.
Last year worldwide headlines crowed that a new experiment may have found particles moving faster than light, disproving a fundamental physics premise posited by Albert Einstein. Follow-up studies and experiments failed to replicate the original results.
As the authors of the new study conclude, “[Philosopher of science Karl] Popper defined a scientifically true effect as that ‘which can be regularly reproduced by anyone who carries out the appropriate experiment in the way prescribed’... Though decades have passed, that is still the operational definition of scientific truth. An effect is not an effect unless it is replicable, and a science is not a science unless it conducts (and values) attempted replications. No matter the outcome, it is indisputably admirable for Bem to encourage and facilitate the independent replication of his experiments. It is, by definition, what any scientist should do.”
Of course, the two studies so far do not completely invalidate Bem’s findings; there is no fixed number of failed replications that proves that an original experiment was fatally flawed. However with each study it becomes more and more likely that the claimed scientific evidence for psychic powers was never real.
There is no shame in proposing a wrong hypothesis or offering evidence of an effect that turns out not to be true; in fact it is exactly that self-correcting mechanism that makes science so robust and fruitful. No experiment is perfect, and there is always a margin of error. The problem is not in making mistakes, but in refusing to acknowledge those mistakes.
Read more at Discovery News
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