Meta-Analysis of Free-Response Studies, 1992–2008: Assessing the Noise Reduction Model in Parapsychology
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Plain English Summary
Published in Psychological Bulletin — one of psychology's most prestigious journals — this meta-analysis (a study combining many experiments) examined 67 ESP studies from 1992 to 2008. Researchers sorted them into ganzfeld (sensory deprivation telepathy tests), relaxation-based approaches like dream telepathy, and plain tests. Ganzfeld won again — participants hit the correct target 32.2% of the time versus 25% expected by chance, with astronomical odds against luck. Relaxation methods also worked; plain tests flopped. The jaw-dropping part: combining 108 ganzfeld studies across 34 years yielded odds so extreme the probability of it being random was less than one in ten thousand trillion. Quieting mental noise genuinely seems to open a door science cannot yet explain.
Research Notes
Published in Psychological Bulletin — one of the strongest endorsements of the ganzfeld paradigm in a mainstream psychology journal. Directly challenged Milton & Wiseman’s (1999) null findings, demonstrated a rebound in ganzfeld effect sizes after an apparent decline, and provided evidence for the noise reduction model. Central to Controversy #1 (Ganzfeld Telepathy).
A meta-analysis of 67 free-response ESP studies (1992–2008) categorized into ganzfeld (29 homogeneous studies), nonganzfeld noise reduction using dream psi, hypnosis, meditation, or relaxation (16 studies), and standard free response (14 homogeneous studies). Ganzfeld studies yielded ES = 0.142 (Stouffer Z = 5.48, p = 2.13 × 10⁻⁸), with a 32.2% hit rate against 25% chance. Nonganzfeld noise reduction produced ES = 0.110 (Z = 3.35, p = 2.08 × 10⁻⁴), while standard free response showed nonsignificant ES = −0.029. Selected participants outperformed unselected participants only in ganzfeld conditions. A combined 108-study ganzfeld database spanning 34 years yielded Stouffer Z = 8.31 (p < 10⁻¹⁶), supporting the noise reduction model and the ganzfeld as the most reliable free-response paradigm.
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- Testing for Questionable Research Practices in a Meta-Analysis: An Example from Experimental Parapsychology — Bierman, Dick J (2016)
- A Bayes Factor Meta-Analysis of Recent Extrasensory Perception Experiments: Comment on Storm, Tressoldi, and Di Risio (2010) — Rouder, Jeffrey N (2013)
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- Explicit Anomalous Cognition: A Review of the Best Evidence in Ganzfeld, Forced-choice, Remote Viewing and Dream Studies — Baptista, Johann (2015)
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📋 Cite this paper
Storm, Lance, Tressoldi, Patrizio E, Di Risio, Lorenzo (2010). Meta-Analysis of Free-Response Studies, 1992–2008: Assessing the Noise Reduction Model in Parapsychology. Psychological Bulletin. https://doi.org/10.1037/a0019457
@article{storm_2010_metaanalysis,
title = {Meta-Analysis of Free-Response Studies, 1992–2008: Assessing the Noise Reduction Model in Parapsychology},
author = {Storm, Lance and Tressoldi, Patrizio E and Di Risio, Lorenzo},
year = {2010},
journal = {Psychological Bulletin},
doi = {10.1037/a0019457},
}