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.
Research Notes
A landmark Bayesian critique of the ganzfeld meta-analytic evidence. Notable for demonstrating that even skeptics must engage with substantial statistical support for psi while showing how randomization quality and study selection critically affect the evidence base. Speaks to the ganzfeld telepathy controversy and the broader meta-analytic methods debate.
Reassessing Storm, Tressoldi, and Di Risio's (2010) meta-analysis of 67 free-response ESP experiments using Bayes factors, the full dataset yields evidence of approximately 6 billion to 1 in favor of psi. However, studies using manual randomization show significantly higher hit rates than computer-randomized studies (BF ≈ 6,350 to 1 for the difference), suggesting procedural flaws rather than genuine psi. Excluding manually randomized studies and including omitted null conditions reduces the evidence to approximately 32–328 to 1 depending on model assumptions. The residual evidence is argued to be unpersuasive given the absence of any plausible mechanism and likely additional unreported null results.
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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},
}