title: Meta-analysis of free-response studies, 1992-2008: assessing the noise reduction model in parapsychology.
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.
authors.affiliation: School of Psychology, University of Adelaide, Adelaide, Australia. lance.storm@adelaide.edu.au
authors.forename: Lance
authors.initials: L
authors.lastname: Storm
authors.forename: Patrizio E
authors.initials: PE
authors.lastname: Tressoldi
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Di Risio
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D004325:Dreams / Q000523:psychology; D006801:Humans; D006990:Hypnosis / Q000379:methods; D019122:Meditation / Q000379:methods / Q000523:psychology; D015201:Meta-Analysis as Topic; D008960:Models, Psychological; D010268:Parapsychology / Q000379:methods*; D010775:Photic Stimulation / Q000379:methods; D012063:Relaxation / Q000523:psychology; D015203:Reproducibility of Results; D012107:Research Design; D013688:Telepathy