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OCR for page 81
POSTSCRIPT
OCR for page 82
i
Postscript
We have been asked to respond to a letter from the committee
raising questions about the presence and consequences of
methodological flaws in the ganzfeld studies discussed by Honorton
(1985), Hyman (1985), Hyman and Honorton (1986), Rosenthal (1986),
and by the present authors of this paper. Our response is in two
parts. In part 1, we examine the likely effects of flaws on the
meta-analytic results of the ganzfeld studies. In part 2, we examine
the results of a series of new studies designed to address the flaws
discussed by Hyman and Honorton in their individual and joint papers.
Flaw Effects
The committee has called our attention to possible flaws in the
randomization procedure employed by Sargent and his colleagues. In
its letter it noted that Honorton agreed with Hyman about the
assignment of these randomization flaws to the Sargent study.
However, Honorton states in two letters that this agreement was not
reached (personal communications of November 25, 1987, and January
15, 1988). Apparently, experts on the ganzfeld research disagree on
whether the Sargent studies' randomization procedures are flawed
given all the evidence available to both, evidence which is
summarized in papers by Blackmore (1987), Harley and Matthews (1987),
and Sargent (1987).
For purposes of this postscript and the following data analyses,
we are going to assume that Hyman is correct in his assignment of
randomization flaws and all other flaws he assigned in his 1985
paper. The heart of the matter is the relationship of flaws to
..t'
research results and that is what our analyses are designed to
investigate. In a 1986 manuscript, Hyman suggested that the
relationship of flaws to study outcomes should
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2
be examined in a multivari ate manner . According ly, that is the nature
of our analyses in our first pass effort to examine the likelihood that
methodological flaws are driving the results of the ganzfeld studies to
an appre ciable degree .
Canonical analysis. The most general of the multi~rariate procedures
examines the maximum relationship that can be found between two sets of
variables, for example, a set of predictor Variables and a set of outcome
variables. In our analysis the predictor variables were Hyman's (1985)
flaw variables of documentation (DOC), feedback (FB), randomization (R),
security (SEC), single target (ST), and statistical analysis (STAT), all
coded as O if adequate or 1 if not adequately done or not adequately specified.
lye outcome variables were the significance level Z and the effect size
Cohen's _. Me adjusted canonical correlation was only .46, a magnitude
that for two-predicted-from-six could have arisen under the null hypothesis
54 times out of 100 (F(12,40) = 0.91). Interestingly, three of the six
flaw variables correlated positively with the flaw canonical variable and
with the outcome canonical variable (DOC, FB, R) but three correlated
negatively (SEC, ST, STAT).
thus, the canonical analysis gives no
support to the hypothesis that the research results are a significant
faction of the set of flaw variables.
Regression analysis. Separate analyses were also done for each of
the outcome variables Z and h. The battery of predictor variables
correlated only .44 with Cohen's h (F(6,21) = 0.84, p = .56) and .57
with Z (F(6,21) = 1.65, p = .183. For neither of ache outcome variables
did any of the six predictors account for a significant proportion of
variance either in zero-order form or after partialing. Since there were
two methods of pa~ialing employed, a total of 36 (3 methods x 6 predictors
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3
l
x 2 outcome variables) it's were computed, none of which reached the .05
i,
level. Regression analyses, therefore, gave no more support than did the
canonical analysis to the hypothesis that ganzfeld research results are
a significant function of the set of flaw variate les .
New Evi dence
Hyman (1985) and Honorton (1985) were agreed tHyman and Honorton, 1986)
that new studies were needed that would take account of the flaws they had
found in their critiques of earlier research. Since our present paper was
completed we have learned of a series of 10 new studies conducted by
Honorton, one of the four investigators singled out by the Committee on
Techniques for the Enhancement of Human Performance as among the best in the
country (Druckman and Swets, 1988, p. 223.
Ibe series of 10 ganzfeld studies yielded a combined Z of 2. 79, ~ = .0026
and amean h of .23. This effect size, based on 10 studies, is only slightly
smaller than the mean effect size of Sargent's nine studies (h = .30) and
is very close to the mean effect size of the remaining 19 studies (h = . 26;
see Table 4a). For the original 28 studies plus the 10 new ones from
Honorton's lab, the combined _ is now 7.10 and the mean effect size is now
an h of .27. knitting Sargent's nine studies changes matters very little--
_ is now 5.74 and h = .25. In short, the new evidence based on studies
designed to meet earlier methodological objections is very consistent with
the earlier evidence and makes the null hypothesis still more implausible.
Conclus ion
Our analysis of the effects of flaws on study outcome lends no support
to the hypothesis that ganzfeld research results are a significant function
of the set of flaw variables. In addition, a series of 10 new studies designed
to control for earlier presumed flaws yielded results quite consistent with
the original set of 28 studies.
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4
References
Blacicmore, S. (1987) . A report of a visit to Carl Sargent's laboratory.
Journal of the Society for Psychical Research, 54, 186-198.
. .
Druckman, D., ~ Swets, J. A. (Eds . ) (1988) .
Issues, theories, and techniques.
Press .
Harley, T., ~ Matthews, G. (1987).
science: A reply to Blackmore.
Research, _, 199 -207
.
Enhancing human performance.
Washington, D . C .: National Academy
Cheating, psi, and the appliance of
Journal of the Society for Psychical
Hyman, R. (19863. To conclude or not to conclude: A reply to the
commentators. Unpublished manuscript, University of Oregon.
Hyman, R., ~ Honorton, C. (19863.
A j Dint communique:
controversy. Jou~-~al of Parapsychology, 50, 351-364.
-
Rosenthal, R. ( 1986) .
replication:
315 -336 .
the psi ganzfeld
Meta-analytic procedures and the nature of
The ganzfeld debate.
Journal of Parapsychology, 50,
.
Sargent, C. (1987). Sceptical fairytales from Bristol. Journal of the
Society for Psychi Cal Re search, 54, 208-218 .
. .
Representative terms from entire chapter:
outcome variables
