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Meta-analysis of Forced-Choice Precognition Experiments
Influence of Moderating Variables In Combination
The above analyses examine the impact of each moderating variable in
isolation.
In this final set of analyses, we explore their joint influence on
precognition performance. For this purpose, we identify two subgroups of
studies. One subgroup is characterized by the use of selected subjects tested
individually with trial-by-trial feedback. We refer to this as the Optimal
group (N - 8 studies). The second group is characterized by the use of
unselected subjects tested in groups with no feedback. We refer to this as
the Suboptimal group (N = 9 studies).
The Optimal studies are contributed by 4 independent investigators and
the Suboptimal studies are contributed by 2 of same 4 investigators. All of
the Optimal studies involve short precognitive time intervals (interval 1)
while the Suboptimal studies involve longer intervals (intervals 5 and 6). All
of the Optimal studies and 5 of the 9 Suboptimal
studies use RNG
methodology. The two groups do not differ significantly in average sample
size. The mean study quality for the Optimal group is significantly higher
than that of the Suboptimal studies (Optimal mean =
6.63, sd =
0.92;
Suboptimal mean = 3.44, sd =
0.53;
t =
8.63, 10 dfy p =
3.3 x 10"6
,
2-tailed).
The combined impact of the moderating variables appears to be quite
strong: 7 of the 8 Optimal studies (87.5%) are independently significant at
the 5%
level, while none of the Suboptimal studies are
statistically
significant. All four investigators contributing studies to the Optimal group
have significant outcomes. The meanz-score for the Optimal group is 2.17
(sd = 0.55) and for the Suboptimal group the mean z
is -0.37 (sd =
1.05).
The difference
is highly significant
(t =
6.13, \2df,p = 2x 10'5
). The
Optimal studies are also significantly less variable (F(7,8) = 3.67, p = .046).
In terms of effect
sizes, the Optimal group
is 9 times larger than the
Suboptimal group (mean ES = 0.055, sd = 0.045 for the Optimal studies,
and 0.006, sd = 0.033) for the Suboptimal studies; this difference is also
significant^ =2.60,15df,p
=.01).
These findings suggest that future studies combining these moderators
should yield especially promising outcomes.
Psychophysical Research Laboratories
Approved For Release 2000/08/08
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Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2
Meta-analysis of Forced-Choice Precognition Experiments
DISCUSSION
Our meta-analysis of forced-choice precognition experiments confirms
the existence of a small but statistically highly significant precognition effect.
Most importantly, the effect appears to be replicable;
significant
confirmations are reported by two dozen investigators using a variety of
methodological paradigms and subject populations.
Estimates of the “filedrawer” problem and consideration of
parapsychological publication practices indicate that the precognition effect
cannot be plausibly explained on the basis of selective publication bias.
Analyses ofprecognitive 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 methodological
artifacts; indeed, several of the
analyses indicate that methodologically superior studies yield stronger
effects than methodologically weaker studies.
Analyses of parapsychological alternatives to precognition, although
limited to the subset of studies using random number tables, provide no
support for the hypothesis that the effect results from the operation of
contemporaneous ESP and PK at the time of randomization.
The most important outcome of the meta-analysis is the identification of
several moderating variables that appear to covary systematically with
precognition performance. The largest effects are observed in studies using
subjects selected on the basis of prior test performance, who are tested
individually, and receive trial-by-trial feedback. The outcomes of studies
combining these factors contrast sharply with the null outcomes associated
with the combination of group testing, unselected subjects, and no feedback
of results. The identification of these moderating variables has important
implications for our understanding of the phenomena and provides a clear
direction for future research.
The existence of moderating variables
indicates that the precognition effect is not merely an unexplained departure
from a theoretical chance baseline, but is rather an effect that covaries with
factors known to influence more familiar aspects of human performance.
It
should now be possible to exploit these moderating factors to increase the
magnitude and reliability of precognition effects in new studies.
Psychophysical Research Laboratories
Approved For Release 2000/08/08
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Approved For Release 2000/08/08
: CIA-RDP96-00789R002200410001-2
Meta-analysis of Forced-Choice Precognition Experiments
While the overall precognition effect size is small, this does not imply that
it has no practical consequences.
It is, for example, of the same order of
magnitude as effect sizes leading to the early termination of several major
medical research studies.
In 1981, the National Heart, Lung, and Blood
Institute discontinued its study of propranolol because the results were so
favorable to the propranolol treatment that it would be unethical to continue
placebo treatment (Kolata, 1981); the effect size is 0.04. More recently, The
Steering Committee of the Physicians’ Health Study Research Group
(1988), in a widely publicized report, terminated its study of the effects of
aspirin in the prevention of heart attacks for the same reason. The aspirin
group suffered 45% fewer heart heart attacks than a placebo control group;
the associated effect size is 0.03.
The search for mechanisms underlying the phenomenon would be
advanced considerably if it were possible to compare the magnitude of the
precognition effect with the effect sizes in “real-time” ESP studies involving
similar testing methods. Tart (1983) claims a robust and highly significant
difference favoring “real-time” ESP in a small subset of forced-choice
precognition and “real-time” ESP studies. However, his analysis is limited
to 85 statistically significant studies (53 studies of “real-time” ESP and 32
precognition studies).
Confirmation of this finding through comparative
analysis of all retrievable “real-time” and precognition studies would have
great value in efforts to model the phenomena and, also, for developing
more effective research methods.
Furthermore, although it is frequently
claimed that ESP is independent of distance, we believe the evidence usually
put forward in support of this claim is very weak and that a more satisfactory
conclusion can only be reached through assessment of all of the evidence.
For these reasons, we recommend that priority be given to a comprehensive
meta-analysis of “real-time” ESP studies.
Psychophysical Research Laboratories
Approved For Release 2000/08/08
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