Feeling the Future: A Meta-Analysis of 90 Experiments on the Anomalous Anticipation of Random Future Events
Patrizio E. Tressoldi
Università di Padova
University of Nantes
Nottingham Trent University
April 11, 2014
In 2011, the Journal of Personality and Social Psychology published a report of nine experiments purporting to demonstrate that an individual’s cognitive and affective responses can be influenced by randomly selected stimulus events that do not occur until after his or her responses have already been made and recorded, a generalized variant of the phenomenon traditionally denoted by the term precognition (Bem, 2011). To encourage replications, all materials needed to conduct them were made available on request. We here report a meta-analysis of 90 experiments from 33 laboratories in 14 countries which yielded an overall effect greater than 6 sigma, z = 6.40, p = 1.2 × 10^-10 with an effect size (Hedges’ g) of 0.09. A Bayesian analysis yielded a Bayes Factor of 1.4 × 10^9, greatly exceeding the criterion value of 100 for “decisive evidence” in support of the experimental hypothesis (Jeffries, 1961). When Bem’s own experiments are excluded from the analysis, the combined effect size for replications by other investigators is 0.06, z = 4.16, p = 1.1 × 10^-5, and the BF value is 3,853, again exceeding the criterion for “decisive evidence.” The number of potentially unretrieved experiments required to reduce the overall effect size of the complete database to a trivial value of 0.01, estimated with Orwin’s fail-safe N, is 544, and six of seven additional statistical tests support the conclusion that the database is not significantly compromised by selection bias, or “p-hacking”—the selective suppression of findings or statistical analyses that failed to yield statistical significance. P-curve analysis, a recently introduced statistical technique (Simonsohn et al., 2014b), estimates the true effect size of our database to be 0.20, virtually identical to the mean effect size of Bem’s original experiments (0.22) and the closely related “presentiment” experiments (0.21). We discuss the controversial status of precognition and other anomalous effects collectively known as psi.
Number of Pages in PDF File: 53
Keywords: precognition, psi, ESP, retrocausation, retro-priming, parapsychology
Date posted: April 12, 2014 ; Last revised: August 4, 2015
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