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Why is PSI so elusive? A review and proposed model
Journal of Parapsychology, The, Sept, 2001 by J.E. Kennedy
The common pattern throughout the history of psychical research has been for the replication rates for each new technique to decline, particularly as more experimenters become involved (Beloff, 1994; Pratt, 1978). For example, a meta-analysis of 30 more recent ganzfeld studies found nonsignificant results overall, with 6 (20%) significant at the .05 level with a one-tailed test and none significant at the .01 level (based on Table 1 in Milton & Wiseman, 1999). Many of these studies had larger sample sizes than the first ganzfeld studies. With the addition of a subsequent significant study, the meta-analysis reaches overall statistical significance, but the replication rate and effect sizes remain significantly lower than for the initial studies (Milton, 1999; replication rate comparison by the present author). Even for lines of research that do not show declines, there is no evidence that research is progressing toward increased occurrence of psi. For example, a meta-analysis of 309 precognition studies found no change in the effect size over a 50-year period (Honorton & Ferrari, 1989).
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As the replication rates in the previous paragraphs indicate, there is no evidence that the ganzfeld procedure increases the occurrence of psi. Direct evaluation cannot be done because very few ganzfeld studies have included a control group. However, a meta-analysis of 78 free-response studies that did not use an altered-state induction procedure found that the effect size was not significantly less than the effect size for the early ganzfeld studies (Milton, 1997). Studies that directly compared altered states with normal states are also inconclusive. With regard to hypnosis, Stanford and Stein (1994) concluded that the findings "make it difficult to draw substantive conclusions from the current database" (p. 235). Experimenter effects may dominate both hypnosis (Schmiedler, 1994, p. 114; Stanford & Stein, 1994) and ganzfeld (Milton, 1999) research.
The traditional strategy of looking for psi-conducive conditions has not been able to advance parapsychology beyond debates about the existence of psi. Factors such as motivation and expectation have little quantified supporting evidence and little predictive value. A review of studies of expectancy and psi concluded that "the data do not clearly support the hypothesis that high expectancy is psi-conducive, and, indeed, there is some indication that low expectancy may be so" (George, 1984, p. 203). Thus, studies of expectancy have exhibited the same type of inconsistent, elusive results as other lines of psi research.
Conclusion
The discussions and hypotheses about psi-conducive psychological conditions basically remain in the domain of lab lore rather than useful, predictive science. This approach has been extensively investigated and, with the possible exception of experimenter effects, does not appear to be addressing the major factors causing the elusive nature of psi.
HYPOTHESIS 4. PSI OCCURS FREQUENTLY WITHOUT BEING NOTICED
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