A Bayes Factor Meta-Analysis of Recent Extrasensory Perception Experiments: Comment on Storm, Tressoldi, and Di Risio (2010)
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Plain English Summary
This paper revisits 67 telepathy experiments — "ganzfeld" studies where someone tries to mentally send images to a receiver. Using Bayes factors (a way of weighing evidence for vs. against a claim), the raw numbers are staggering: about 6 billion to 1 favoring psychic phenomena. But studies using manual randomization got much better results than computer-randomized ones — a red flag, since sloppy randomization lets patterns leak through. Strip those out and add back overlooked negative results, and the evidence drops to 32-328 to 1. The authors say that's unconvincing with no explanation for how ESP would work. A great example of how experimental details make extraordinary evidence balloon or deflate.
Abstract
Psi phenomena, such as mental telepathy, precognition, and clairvoyance, have garnered much recent attention. We reassess the evidence for psi effects from Storm, Tressoldi, and Di Risio's (2010) meta-analysis. Our analysis differs from Storm et al.'s in that we rely on Bayes factors, a Bayesian approach for stating the evidence from data for competing theoretical positions. In contrast to more conventional analyses, inference by Bayes factors allows the analyst to state evidence for the no-psi-effect null as well as for a psi-effect alternative. We find that the evidence from Storm et al.'s presented data set favors the existence of psi by a factor of about 6 billion to 1, which is noteworthy even for a skeptical reader. Much of this effect, however, may reflect difficulties in randomization: Studies with computerized randomization have smaller psi effects than those with manual randomization. When the manually randomized studies are excluded and omitted studies included, the Bayes factor evidence is at most 330 to 1, a greatly attenuated value. We argue that this value is unpersuasive in the context of psi because there is no plausible mechanism and because there are almost certainly omitted replication failures.
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Cites
- Feeling the Future: Experimental Evidence for Anomalous Retroactive Influences on Cognition and Affect — Bem, Daryl J (2011)
- Meta-Analysis That Conceals More Than It Reveals: Comment on Storm et al. (2010) — Hyman, Ray (2010)
- A Joint Communiqué: The Psi Ganzfeld Controversy — Hyman, Ray (1986)
- Why Psychologists Must Change the Way They Analyze Their Data: The Case of Psi — Wagenmakers, Eric-Jan (2011)
- Extraordinary Claims Require Extraordinary Evidence: The Case of Non-Local Perception, A Classical and Bayesian Review of Evidences — Tressoldi, Patrizio E (2011)
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📋 Cite this paper
Rouder, Jeffrey N, Morey, Richard D, Province, Jordan M (2013). A Bayes Factor Meta-Analysis of Recent Extrasensory Perception Experiments: Comment on Storm, Tressoldi, and Di Risio (2010). Psychological Bulletin. https://doi.org/10.1037/a0029008
@article{rouder_2013_bayes_factor_esp,
title = {A Bayes Factor Meta-Analysis of Recent Extrasensory Perception Experiments: Comment on Storm, Tressoldi, and Di Risio (2010)},
author = {Rouder, Jeffrey N and Morey, Richard D and Province, Jordan M},
year = {2013},
journal = {Psychological Bulletin},
doi = {10.1037/a0029008},
}