A quantitative digest of the ESP-Nexus structured study database for Ganzfeld ESP: 32 studies spanning 1978–2024, with every figure traceable to its source. ESP-Nexus reports what the studies found and takes no position on whether the effects are genuine.
The ganzfeld database spans studies from 1980 to 2024, with meta-analytic pooled estimates showing a consistent pattern of small-to-moderate positive effects across most analyses. Effect sizes range from near-zero, such as Milton's (1999) z_over_sqrt_n of 0.013 across 30 studies, to more substantial values like Honorton's (1990) Cohen's h of 0.29 across 39 studies and Harris's (2024) Cohen's h of 0.27 across 38 studies. Several meta-analyses report statistically notable aggregate z-scores, including Storm (2010) at z 8.13 across 102 studies and Pooley (2023) at z 5.81 across 41 studies. Tressoldi's registered reports, however, yielded considerably smaller estimates of 0.088 (Hedges' g, 2021) and 0.074 (z_over_sqrt_n, 2024).
Heterogeneity complicates interpretation substantially. At least two pooled analyses show I² at or above 50%, and five results fall null or below chance, including Milton's (1999) analyses yielding near-zero effects. Individual study outcomes vary considerably, from Westerlund (2006) at p = .383 to Morris (2001) reporting a hit rate of 0.40. This spread suggests the evidence base is not uniform, and the sources of between-study variability, whether procedural, population-based, or related to methodological quality, remain unresolved in the literature.
Pooled meta-analytic effects
- Tressoldi (2024), F1000Research: ES 0.074 (z_over_sqrt_n) (k = 78)
- Harris (2024), Journal of Anomalous Experience and Cognition (JAEX): ES 0.27 (cohens_h) (k = 38)
- Pooley (2023), Journal of Anomalous Experience and Cognition: z 5.81 (k = 41)
- Tressoldi (2021), F1000Research: ES 0.088 (hedges_g) (k = 113)
- Williams (2011), Journal of Scientific Exploration: z 6.36 (k = 59)
- Storm (2010), Psychological Bulletin: ES 0.142 (z_over_sqrt_n) (k = 29)
- Tressoldi (2010), NeuroQuantology: z 2.04 (k = 30)
- Storm (2001), Psychological Bulletin: ES 0.138 (z_over_sqrt_n) (k = 79)
- Milton (1999), Psychological Bulletin: ES 0.013 (z_over_sqrt_n) (k = 30)
- Milton (1999), The Journal of Parapsychology: ES 0.038 (z_over_sqrt_n) (k = 39)
- Milton (1997), The Journal of Parapsychology: z 3.37 (k = 42)
- Honorton (1990), Research in Parapsychology (RIP) conference proceedings: ES 0.29 (cohens_h) (k = 39)
The evidence
| Paper | Reported finding | Effect / significance | Basis |
|---|---|---|---|
| Tressoldi et al. (2024), F1000Research [source] | Overall pooled ES – frequentist random-effects. | ES 0.074, p = 9 × 10−4 | 78 studies |
| Lieb et al. (2024), Zeitschrift fuer Anomalistik / Journal of Anomalistics [source] | H1a confirmatory receiver direct-hit rate. | ES 0.12, z = 0.83, p = .199, hit rate 0.3125 | N = 48 trials; 48 participants |
| Harris et al. (2024), Journal of Anomalous Experience and Cognition (JAEX) [source] | 28 original + 10 new studies combined. | ES 0.27, z = 7.1 | 38 studies |
| Lieb et al. (2024), Journal of Anomalistics / Zeitschrift für Anomalistik [source] | H1a: Receiver hit rate across all 48 trials. | ES 0.12, z = 0.83, p = .199, hit rate 0.3125 | N = 48 trials; 96 participants |
| Pooley et al. (2023), Journal of Anomalous Experience and Cognition [source] | Descriptive overall hit rate across all 41 studies. | z = 5.81, p < .001, hit rate 0.32 | 41 studies; N = 1624 trials; 1496 participants |
| Tressoldi et al. (2021), F1000Research [source] | Overall effect size – Frequentist random-effects. | ES 0.088, p = 1.7 × 10−5 | 113 studies |
| Watt et al. (2020), Journal of Parapsychology [source] | H1 – Precognition direct-hit rate. | ES 0.25, z = 1.94, p = .03, hit rate 0.37 | N = 60 trials; 60 participants |
| Williams (2011), Journal of Scientific Exploration [source] | 59-study post-communique collection – combined hit rate. | z = 7.37, p = 8.6 × 10−14, hit rate 0.31 | 59 studies; N = 2832 sessions |
| Storm et al. (2010), Psychological Bulletin [source] | Category 1 – homogeneous 29-study set. | ES 0.142, z = 5.48, p = 2.1 × 10−8, hit rate 0.322 | 29 studies; N = 1498 trials |
| Tressoldi et al. (2010), NeuroQuantology [source] ⚠ relayed figures | Figures are Milton and Wiseman (1999) — as relayed/re-derived in this paper, not its own experiment. Milton & Wiseman meta-analysis. | z = 2.04, p = .041 | 30 studies |
| Pütz et al. (2008), Zeitschrift für Anomalistik / Journal of Anomalistics [source] | Correct target identification hit rate, single trials. | p = .039, hit rate 0.325 | N = 120 trials; 80 participants |
| Lau (2004) | Six long ganzfeld studies – final cumulative meta-analytic hit rate. | hit rate 0.3 | 6 studies; N = 120 trials |
| Stevens (2004), Journal of Parapsychology [source] | ESP success by target rank – total. | ES 0.49, p = .33, hit rate 0.24 | N = 100 trials |
| Storm et al. (2001), Psychological Bulletin [source] | Unified Old + New Ganzfeld Database – grand pooled effect. | ES 0.138, z = 5.66, p = 7.8 × 10−9, hit rate 0.31 | 79 studies |
| Milton et al. (1999), Psychological Bulletin | Main effect – 30 new ganzfeld studies. | ES 0.013, z = 0.7, p = .24 | 30 studies; N = 1198 trials |
| Milton (1999), The Journal of Parapsychology [source] | Updated recent-ganzfeld cumulation 1987-March 1999. | ES 0.038, z = 2.28, p = .011 | 39 studies; N = 1460 trials |
| Utts (1999), Journal of Scientific Exploration | Combined ganzfeld + remote viewing. | hit rate 0.34 | N = 2097 sessions |
| Symmons et al. (1997), Proceedings of the 40th Annual Convention of the Parapsychological Association [source] | Overall direct hits – subjects' own ratings. | ES 0.36, z = 2.506, p < .01, hit rate 0.412 | N = 51 trials; 51 participants |
| Dalton (1997), Proceedings of the 40th Annual Convention of the Parapsychological Association [source] | Overall study direct-hit rate. | ES 0.46, hit rate 0.47 | N = 128 trials; 128 participants |
| Milton (1997), The Journal of Parapsychology [source] | Ganzfeld studies – Sums of ranks, Stouffer z. | z = 3.37, p = 3.7 × 10−4 | 42 studies |
What is unsettled
- Reported directions disagree across studies (some positive, some null or below-chance).
- High between-study heterogeneity (I² ≥ 50%) in 2 pooled result(s).
- 4 result(s) report a null or below-chance (negative) effect.
Source: ESP-Nexus structured study database, 32 studies. 33 born-digital figures; OCR-derived figures awaiting source-verification are excluded from this digest. Effect sizes are shown only where a standardized metric is recorded.