Does the ganzfeld produce replicable evidence for telepathy?
Quick Summary
The ganzfeld protocol β in which a "receiver" in sensory deprivation attempts to identify a target being viewed by a remote "sender" β is the single most debated experimental paradigm in parapsychology.
The central question is whether the hit rate (typically reported around 32% against a 25% chance baseline) reflects genuine anomalous information transfer or persistent methodological and statistical artifacts.
Current Consensus
The ganzfeld remains one of parapsychology's most-replicated paradigms, but the debate turns on study inclusion criteria and quality thresholds. Pro-psi meta-analyses (Storm 2010, 2020) find a robust effect across 108 studies spanning 1992-2018 with no decline over 44 years (ES~0.13 for ganzfeld); critical meta-analyses (Milton & Wiseman 1999) argue the effect vanishes when stricter quality filters are applied, and Rouder et al. (2013) attribute much of the effect to manually randomized studies. The impasse reflects deeper disagreements about what counts as an adequate control in this domain. New work using neuroimaging (Moulton & Kosslyn 2008) has generally not supported the effect, while behavioral ganzfeld studies continue to produce above-chance hit rates, particularly with selected participants. The 2024 Tressoldi & Storm registered-report meta-analysis adds pre-registered rigor to the pro-psi position.
Evidence Breakdown
Based on 28 papersSupporting Evidence
Does Psi Exist? Replicable Evidence for an Anomalous Process of Information Transfer
Bem & Honorton (1994) -- Autoganzfeld experiments yield 32% hit rate (z=2.89, p=.002, 329 sessions) with automated computer-controlled protocols; reviews 28 prior ganzfeld studies (composite z=6.60...
Meta-Analysis of Free-Response Studies, 1992β2008: Assessing the Noise Reduction Model in Parapsychology
Storm, Tressoldi & Di Risio (2010) -- Meta-analysis of free-response studies (1992-2008) finds significant cumulative effect
Meta-Analysis of Free-Response Studies 2009-2018: Assessing the Noise-Reduction Model Ten Years On
Storm & Tressoldi (2020) -- 10-year update meta-analysis (2009-2018): 43 new studies combined with 1992-2008 databases yield k=108 total; ganzfeld (k=38) ES=0.133, 95% CI [0.071, 0.194], Stouffer Z...
Extrasensory Perception and Quantum Models of Cognition
Tressoldi, Storm & Radin (2010) -- Narrative review synthesizing all six ganzfeld meta-analyses (108 studies, 4,196 trials): overall hit rate 31.5% vs. 25% chance, Ο = 0.58 (95% CI .56β.60, z = 9.9...
Does Psi Exist? Comments on Milton and Wiseman's (1999) Meta-Analysis of Ganzfeld Research
Storm & Ertel (2001) -- Rebuttal to Milton & Wiseman (1999); unified 79 ganzfeld/autoganzfeld studies yielding ES = 0.138, Z = 5.66, p = 7.78 Γ 10β»βΉ; 31% hit rate vs. 25% MCE; significant bidirecti...
Updating the Ganzfeld Database: A Victim of Its Own Success?
Bem, Palmer & Broughton (2001) -- Meta-analysis of 40 post-1987 ganzfeld studies: 10 new studies yield 36.7% hit rate (Z=3.97, p=3.5Γ10β»β΅); all 40 combined yield 30.1% (Z=2.59, p=.0048). Three inde...
On the Correspondence Between Dream Content and Target Material Under Laboratory Conditions: A Meta-Analysis of Dream-ESP Studies, 1966-2016
Storm et al. (2017) -- Meta-analysis of 50 dream-ESP studies (1966-2016) yields ES=0.20, Stouffer Z=5.32, p=5.19Γ10^-8; both Maimonides and non-MDL studies significant
Psychology and Anomalous Observations: The Question of ESP in Dreams
Child (1985) -- Independent reanalysis of Maimonides dream ESP data in *American Psychologist*: hits exceeded misses on 15 of 15 segments (sign test p < .0001); combined p < .000002 for outside jud...
The Einstein-Podolsky-Rosen Paradox in the Brain: The Transferred Potential
Grinberg-Zylberbaum et al. (1994) -- Foundational 'transferred potential' study: 7 pairs meditated together then separated into Faraday chambers 14.5 m apart; ~25% of pairs showed transferred poten...
Evidence of Correlated Functional Magnetic Resonance Imaging Signals Between Distant Human Brains
Standish et al. (2003) -- First fMRI demonstration of distant brain correlations: receiver in Faraday-shielded MRI scanner showed significant BOLD activation (P < .001) in visual cortex areas 18-19...
Electroencephalographic Evidence of Correlated Event-Related Signals Between the Brains of Spatially and Sensory Isolated Human Subjects
Standish et al. (2004) -- Largest EEG correlation study (N=60, 30 pairs): 5 of 60 subjects (8.3%) showed significant brain activation (p<0.01) during partner's flicker condition; Stouffer z=-3.28 (...
Event-Related Electroencephalographic Correlations Between Isolated Human Subjects
Radin (2004) -- Extends Grinberg-Zylberbaum's transferred-potential paradigm: 13 pairs had EEGs recorded while the sender was stimulated by receiver's live video image; receiver in double steel-wal...
Replicable Functional Magnetic Resonance Imaging Evidence of Correlated Brain Signals Between Physically and Sensory Isolated Subjects
Richards et al. (2005) -- fMRI and EEG study of one pre-selected pair: subject DW showed significant BOLD activation in visual cortex BA 17/18/19 correlated with isolated partner's flickering stimu...
Mental Connection at Distance: Useful for Solving Difficult Tasks?
Tressoldi et al. (2011) -- Forced-choice telepathy without sensory deprivation: Exp1 (N=40) Chinese ideogram identification with distant helper yielded 10.3% above MCE (ES=0.44, BF10=23.8); Exp2 (N...
Extraordinary Claims Require Extraordinary Evidence: The Case of Non-Local Perception, a Classical and Bayesian Review of Evidences
Tressoldi (2011) -- Bayesian meta-analysis of ganzfeld database yields BF=18.8 million in favor of H1, arguing this meets "extraordinary evidence" standard
Meta-Analysis of Free-Response ESP Studies Without Altered States of Consciousness
Milton (1997) -- Meta-analysis of 78 non-ganzfeld free-response ESP studies (1964β1992): mean ES = 0.16, Stouffer Z = 5.72, p < 5.4 Γ 10β»βΉ across 2,682 trials; file-drawer of 866 null studies neede...
Replication and Meta-Analysis in Parapsychology
Utts (1991) -- Survey of four psi meta-analyses in *Statistical Science* concludes autoganzfeld hit rate of 34.4% (p=0.00005, h=0.20) constitutes an anomalous effect needing explanation; includes c...
A Joint CommuniquΓ©: The Psi Ganzfeld Controversy
Hyman & Honorton (1986) -- Joint communiquΓ© by the leading skeptic and leading proponent replacing a planned exchange. Both authors agree the ganzfeld database shows "an overall significant effect ...
Explicit Anomalous Cognition: A Review of the Best Evidence in Ganzfeld, Forced-choice, Remote Viewing and Dream Studies
Baptista, Derakhshani & Tressoldi (2014) -- Comprehensive review of ganzfeld evidence including new analyses of Storm et al. (2010) database; selected participants produce 40.1% hit rate vs. 27.3% ...
Stage 2 Registered Report: Anomalous Perception in a Ganzfeld Condition - A Meta-Analysis of More Than 40 Years Investigation
Tressoldi & Storm (2024) -- Stage 2 Registered Report meta-analysis of 78 ganzfeld studies (113 effect sizes, 1974-2020): overall ES = 0.08 (95% CI [0.04, 0.12]; BFββ = 89.5); passes 4 publication ...
Critical Evidence
Does Psi Exist? Lack of Replication of an Anomalous Process of Information Transfer
Milton & Wiseman (1999) -- Meta-analysis of post-1987 ganzfeld studies finds no significant effect, suggesting earlier results were driven by methodological flaws
Anomaly or Artifact? Comments on Bem and Honorton
Hyman (1994) -- Reanalysis of autoganzfeld data finds hit rate strongly correlated with target occurrence frequency (Spearman r = .83, p = .013) and a significant target-occurrence Γ experimenter-p...
Evaluation of a Program on Anomalous Mental Phenomena
Hyman (1996) -- Commissioned evaluation of SRI/SAIC program argues autoganzfeld data show key inconsistencies: static targets yielded zero effect size despite comprising the bulk of the original ga...
Meta-Analysis That Conceals More Than It Reveals: Comment on Storm et al. (2010)
Hyman (2010) -- Commentary on Storm et al.'s ganzfeld meta-analysis demonstrating that apparent consistency is manufactured by outlier removal, combining heterogeneous databases, and confusing fail...
Why Most Published Research Findings Are False
Ioannidis (2005) -- The mathematical framework explaining why small-sample ganzfeld studies (typically n < 50 per lab) with small effects (~32% hit rate vs 25% chance) are likely false positives; i...
Using Neuroimaging to Resolve the Psi Debate
Moulton & Kosslyn (2008) -- Harvard fMRI study with 16 sender-receiver pairs (including twins, couples): behavioral guessing at exact chance (50.0%, 3,687 trials), no significant brain activation d...
Testing for Questionable Research Practices in a Meta-Analysis: An Example from Experimental Parapsychology
Bierman, Spottiswoode & Bijl (2016) -- Monte Carlo simulation of seven QRPs applied to 78 post-1985 ganzfeld studies: with realistic QRP prevalence rates, simulations account for ~60% of the report...
A Bayes Factor Meta-Analysis of Recent Extrasensory Perception Experiments: Comment on Storm, Tressoldi, and Di Risio (2010)
Rouder, Morey & Province (2013) -- Bayesian reanalysis of Storm et al.'s (2010) 67 free-response studies: full dataset yields BFββ β 6 billion, but manually randomized studies show significantly hi...