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Type: Journal article
Title: Meta-analysis of free-response studies, 1992-2008: assessing the noise reduction model in parapsychology
Author: Storm, L.
Tressoldi, P.
Di Risio, L.
Citation: Psychological Bulletin, 2010; 136(4):471-485
Publisher: Amer Psychological Assoc
Issue Date: 2010
ISSN: 0033-2909
Statement of
Lance Storm, Patrizio E. Tressoldi and Lorenzo Di Risio
Abstract: We report the results of meta-analyses on 3 types of free-response study: (a) ganzfeld (a technique that enhances a communication anomaly referred to as "psi"); (b) nonganzfeld noise reduction using alleged psi-enhancing techniques such as dream psi, meditation, relaxation, or hypnosis; and (c) standard free response (nonganzfeld, no noise reduction). For the period 1997-2008, a homogeneous data set of 29 ganzfeld studies yielded a mean effect size of 0.142 (Stouffer Z = 5.48, p = 2.13 x 10(-8)). A homogeneous nonganzfeld noise reduction data set of 16 studies yielded a mean effect size of 0.110 (Stouffer Z = 3.35, p = 2.08 x 10(-4)), and a homogeneous data set of 14 standard free-response studies produced a weak negative mean effect size of -0.029 (Stouffer Z = -2.29, p = .989). The mean effect size value of the ganzfeld database was significantly higher than the mean effect size of the standard free-response database but was not higher than the effect size of the nonganzfeld noise reduction database [corrected].We also found that selected participants (believers in the paranormal, meditators, etc.) had a performance advantage over unselected participants, but only if they were in the ganzfeld condition.
Keywords: ESP; free response; ganzfeld; meta-analysis; psi; noise reduction model; parapsychology
Rights: © 2010 American Psychological Association
RMID: 0020100319
DOI: 10.1037/a0019457
Appears in Collections:Psychology publications

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