Updating the Ganzfeld Database: A Victim of Its Own Success?
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Plain English Summary
Here's a detective story about telepathy research. The ganzfeld procedure (where a 'receiver' relaxes in sensory isolation while a 'sender' transmits mental images) had shown promising results, but a 1999 meta-analysis declared the effect had vanished. Bem, Palmer, and Broughton fired back, arguing the disappearance was an illusion from lumping good and sloppy studies together. They found 10 overlooked studies that alone hit 36.7% success (chance is 25%). The key move: independent raters scored how closely each study followed the standard recipe. Studies sticking to protocol succeeded at about 31%. Studies that deviated? A flat 24% -- basically chance. The practical takeaway: when a promising experiment stops 'working,' maybe the question isn't whether the effect is real, but whether people are running it correctly.
Research Notes
Direct response to Milton and Wiseman's (1999) null meta-analysis. Introduces protocol adherence as key moderator variable explaining apparent replication failures. Important methodological lesson: heterogeneity in meta-analyses can obscure real effects. The 10 new studies were located by examining six major parapsychology publication outlets; many were completed but unpublished before Milton-Wiseman cutoff. Raters achieved good inter-rater reliability (Cronbach's alpha=.78) despite limited prior ganzfeld familiarity. Extends hyman_honorton_1986_joint_communique by providing quantitative resolution to the controversy.
Meta-analysis of 40 ganzfeld studies published after Bem and Honorton (1994), including 30 from Milton and Wiseman (1999) plus 10 new studies. The 10 new studies yield hit rate of 36.7% (Z=3.97, p=3.5×10⁻⁵); all 40 combined yield 30.1% (Z=2.59, p=.0048). Three independent raters rated each study's adherence to standard ganzfeld protocol. Standardness ratings significantly correlated with effect size (r=.31, p=.024). Standard replications (n=29) achieved 31.2% hit rate (ES=.096, Z=3.49, p=.0002), within confidence intervals of earlier studies. Non-standard replications (n=9) achieved only 24.0% (ES=−.10, Z=−1.30, ns). Concludes that ganzfeld studies adhering to standard protocol continue to replicate with effect sizes comparable to previous studies.
Related Papers
Cites
- Does Psi Exist? Replicable Evidence for an Anomalous Process of Information Transfer — Bem, Daryl J (1994)
- Does Psi Exist? Lack of Replication of an Anomalous Process of Information Transfer — Milton, Julie (1999)
- "Future Telling": A Meta-Analysis of Forced-Choice Precognition Experiments, 1935-1987 — Honorton, Charles (1989)
- Does Psi Exist? Comments on Milton and Wiseman's (1999) Meta-Analysis of Ganzfeld Research — Storm, Lance (2001)
Critiqued By
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📋 Cite this paper
Bem, Daryl J, Palmer, John, Broughton, Richard S (2001). Updating the Ganzfeld Database: A Victim of Its Own Success?. Journal of Parapsychology.
@article{bem_palmer_broughton_2001_updating_ganzfeld,
title = {Updating the Ganzfeld Database: A Victim of Its Own Success?},
author = {Bem, Daryl J and Palmer, John and Broughton, Richard S},
year = {2001},
journal = {Journal of Parapsychology},
}