James Randi, magician and scientific skeptic, has compared those who believe in the paranormal to “unsinkable rubber ducks”: after a particular claim has been thoroughly debunked, the ducks submerge, only to resurface again a little later to put forward similar claims.
In light of this analogy, it comes as no surprise that Bem and colleagues have produced a new paper claiming that people can look into the future. The paper is titled “Feeling the Future: A Meta-Analysis of 90 Experiments on the Anomalous Anticipation of Random Future Events” and it is authored by Bem, Tressoldi, Rabeyron, and Duggan.
Several of my colleagues have browsed Bem's meta-analysis and have asked for my opinion. Surely, they say, the statistical evidence is overwhelming, regardless of whether you compute a p-value or a Bayes factor. Have you not changed your opinion? This is a legitimate question, one which I will try and answer below by showing you my review of an earlier version of the Bem et al. manuscript.
I agree with the proponents of precognition on one crucial point: their work is important and should not be ignored. In my opinion, the work on precognition shows in dramatic fashion that our current methods for quantifying empirical knowledge are insufficiently strict. If Bem and colleagues can use a meta-analysis to demonstrate the presence of precognition, what should we conclude from a meta-analysis on other, more plausible phenomena?
Disclaimer: the authors have revised their manuscript since I reviewed it, and they are likely to revise their manuscript again in the future. However, my main worries call into question the validity of the enterprise as a whole.
To keep this blog post self-contained, I have added annotations in italics to provide context for those who have not read the Bem et al. manuscript in detail.
My review of Bem, Tressoldi, Rabeyron, and DugganRead more...