Rg. Stanford et Ag. Stein, A METAANALYSIS OF ESP STUDIES CONTRASTING HYPNOSIS AND A COMPARISON CONDITION, Journal of parapsychology, 58(3), 1994, pp. 235-269
This meta-analysis examined 25 ESP studies from 12 chief investigators
. No potential moderator variable correlated significantly with ESP ef
fect size (pi) under either hypnosis or the comparison condition. Ther
e was cumulative ESP-test significance for hypnosis, but this signific
ance may be inflated by nonindependence of study outcomes within chief
investigator. For both experimental conditions, chief investigator wa
s associated with significant heterogeneity of outcomes. In ESP analys
es based on chief investigator, neither the contrast, nor either of th
e experimental conditions, showed significance. The sum of scored flaw
s per study did not correlate significantly with outcomes, but the mea
n number of such flaws was substantial. For the same-subjects studies
suitable for analysis, testing order interacted significantly with the
experimental manipulation. The hypnosis-comparison contrast was signi
ficant only when the comparison condition preceded hypnosis. This sign
ificance was due, substantially, to psi-missing in the comparison cond
ition. These and other findings make it difficult to draw substantive
conclusions from the current database.