: CIA-RDP96-00789R002200610001-0 Approved For Release 2000/08/08 300 The Journal of Parapsychology TABLE 7 IMPACT OF MODERATORS IN COMBINATION “Optimal” studies “Suboptimal” studies N studies 8 9 Combined z 6.14 —1.29 Studies with p < .05 87.5% 0.0% Mean ES .055 .005 SDes 045 -035 1115) = 2.61, p = 01 y = .559 vn These results are quite striking and suggest that future studies combining these moderators should yield especially reliable effects. SUMMARY AND CONCLUSIONS Our meta-analysis of forced-choice precognition experiments confirms the existence of a small but highly significant precognition effect. The effect appears to be replicable; significant outcomes are reported by 40 investigators using a variety of methodological par- adigms and subject populations. The precognition effect is statistically very robust: it remains highly significant despite elimination of studies with z scores in the upper and lower 10% of the z-score distribution and when a third of the remaining investigators—the major contributors of precog- nition studies—are eliminated. Estimates of the “filedrawer” problem and consideration of para- psychological publication practices indicate that the precognition ef- fect cannot plausibly be explained on the basis of selective publica- tion bias. Analyses of precognition effect sizes in relation to eight measures of research quality fail to support the hypothesis that the observed effect is driven to any appreciable extent by methodolog- ical flaws; indeed, several analyses indicate that methodologically su- perior studies yield stronger effects than methodologically weaker studies. Analyses of parapsychological alternatives to precognition, al- though limited to the subset of studies using random number tables, provide no support for the hypothesis that the effect results from A Meta-Analysis of Forced-Choice Precognition Experiments 301 ‘he operation of contemporaneous ESP and PK at the ume of ran- domization. Although the overall precognition effect size is small, this does iot imply that it has no practical consequences. It is, for example, of the same order of magnitude as effect sizes leading to the early ermination of several major medical research studies. In 1981, the National Heart, Lung, and Blood Institute discontinued its study of sropranolol because the results were so favorable to the propranolol reatment that it would be unethical to continue placebo treatment Kolata, 1981); the effect size was 0.04. More recently, The Steering committee of the Physicians’ Health Study Research Group (1988), n a widely publicized report, terminated its study of the effects of ispirin in the prevention of heart attacks for the same reason. The ispirin group suffered significantly fewer heart attacks than a pla- ‘ebo control group; the associated effect size was 0.03. ‘The most important outcome of the meta-analysis is the identi- ication of several moderating variables that appear to covary sys- ematically with precognition performance. The largest effects are ibserved in studies using subjects selected on the basis of prior test yerformance, who are tested individually, and who receive trial-by- rial feedback. The outcomes of studies combining these factors con- rast sharply with the null outcomes associated with the combination f group testing, unselected subjects, and no feedback of results. Be- ause the two groups of studies were conducted by a subset of the ame investigators, it is unlikely that the observed difference in per- ormance is due to experimenter effects. Indeed, these outcomes inderscore the importance of carefully examining differences in ubject populations, test setting, and so forth, before resorting to acile “explanations” based on psi-mediated experimenter effects or he “elusiveness of psi.” The identification of these moderating variables has important nplications for our understanding of the phenomena and provides clear direction for future research. The existence of moderating ariables indicates that the precognition effect is not merely an nexplained departure from a theoretical chance baseline, but ather is an effect that covaries with factors known to influence yore familiar aspects of human performance. It should now be pos- ble to exploit these moderating factors to increase the magnitude nd reliability of precognition effects in new studies. REFERENCES KERS, C. (1987). Parapsychology is science, but its findings are inconclusive. Behavioral and Brain Sciences, 10, 566-568. : CIA-RDP96-00789R002200610001-0 Approved For Release 2000/08/08