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Table 2
Study 302: Proportion of Sessions in which Each Video Clip was Ranked First when it was a Target
and when it was a Decoy
Video Clip
Relative
Frequency
as Target
Ranked First
when
Target
Ranked First
when
Decoy
Difference
Fisher’s
Exact
P
Tidal Wave
.28
.57
.11
+.46
.032
(7/25)
(4/7)
(2/18)
Snakes
.12
.67
.05
+.62
.029
(3/25)
(2/3)
(1/22)
High-Speed Sex
.16
.25
.05
+.20
.300
(4/25)
(1/4)
(1/21)
Bugs Bunny
.44
.82
.36
+.46
.027
(11/25)
(9/11)
(5/14)
Means
.58
.14
+.44
-
sions. If there were such an effect, then studies with fewer
sessions
would show
larger
effect
sizes
because
they
would end before a decline could set in. To check this pos-
sibility, we computed point-biserial correlations between
hits (=
1) or misses (= 0) and the session number within
each of the
studies.
All of the correlations hovered
around zero; six were positive, four were negative, and the
overall mean was +.03, indicating that hits were actually
slightly more likely to occur in later sessions of a study
than in earlier' ones.
An inspection of Table 1 reveals that the negative corre-
lation
derives primarily from the two studies with the
largest effect sizes: the 20 sessions with the Juilliard stu-
dents and the 7 sessions of Study 201, the study specifi-
cally designed to retest the most promising participants
from the previous studies. Accordingly, we believe that
the larger effect sizes of these two studies—and hence the
significant negative correlation between number of ses-
sions and effect size—reflects a genuinely higher psi abil-
ity of participants in these two small but highly selected
samples.
Study 302. All of the studies except Study 302 randomly
sampled from a pool of 160 static and dynamic targets.
Study 302 sampled from
a
single, dynamic target
set
which contained one video clip that had been correctly
identified
several times in the previous ten studies—
a
scene of a tidal wave from the movie Clash ofthe Titans—
and one clip that had never been correctly identified—
a
high-speed sex scene from Clockwork Orange. The set also
contained a scene of crawling snakes from a TV documen-
tary and a scene from a Bugs Bunny cartoon.
The experimental design called for this study to con-
tinue until each of the clips had served as the target 15
times. Unfortunately, the premature termination of this
study at 25 sessions left an imbalance in the frequency
with which each clip had served as the target. This means
that the chance expectation of .25 used as the baseline for
evaluating the results in the other studies cannot be ap-
plied to this study. More importantly,
it means that the
high hit rate observed (64%) could well be inflated by re-
sponse biases.
To illustrate, water imagery is frequently reported by
receivers in ganzfeld sessions whereas sexual imagery is
rarely reported.
(It is reasonable
to suppose that some
participants might be reluctant both to report sexual im-
agery and to give the highest rating to the sex-related
clip.) If a video clip containing popular imagery (like wa-
ter) happens to appear as a target more frequently than a
clip containing unpopular imagery (like sex), a high
hit
rate might simply reflect the coincidence of those frequen-
cies of occurrence with participants’ response biases. And,
as the first column of Table 2 reveals, the tidal wave clip
did in fact appear more frequently as the target than did
the sex clip. TTie Bugs Bunny clip was even more frequent,
appearing as the target in 11 of the 25 (44%) sessions.
We can assess the damage in two ways. First, we can
ask for each of the four clips whether it was selected as
the target
(i.e., ranked in
first place) significantly more
frequently when it was the target than when it was one of
the three control clips (decoys). This comparison, which
controls
for the baseline popularity of the themes and
images
within
each
clip,
is shown
in
the
remaining
columns of Table 2.
As can be seen, each of the four clips was selected as the
target relatively more frequently when it was the target
than when it was a decoy, a difference that is significant
for three of the four clips. On average, a clip was identified
as the target 58% of the time when
it was the target
compared with only 14% of the time when it was a decoy.
In other words, there is an effect over and above that pro-
duced by response bias.
Next, we can calculate a conservative estimate of that
remaining effect by imagining a hypothetical
set of in-
formed receivers who were able to maximally exploit the
unequal target frequencies to achieve the highest possible
hit rate. Their optimal (non-psi) strategy would be to iden-
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tify the most frequent clip (Bugs Bunny) as the target in
eveiy session, thereby achieving a hit rate of 44%. This
figure thus represents the hit rate expected if response bi-
ases were malting their maximum possible contribution to
the hit rate—a worst case baseline for evaluating any re-
maining psi effect. When the observed hit rate of 64% is
compared with a hypothetical hit rate of 44%, the effect
size (h ) is .40. As shown in Table
1, this is equivalent to a
four-alternative
hit rate of (coincidentally) 44% or a n
value of .70 and is statistically significant
(
z
= 2.02, p =
.022 ).
Dynamic versus static targets. The success of Study 302
raises the question of whether dynamic targets are,
in
general, more effective than static targets. This possibility
was also suggested by the earlier meta-analysis, which
found that studies using multiple-image
targets
( View
Master
stereoscopic
slide
reels)
obtained
significantly
higher hit rates than did studies using single-image tar-
gets. By adding motion and sound, the video clips might
be thought of as high-tech versions of the View Master
reels.
The ten autoganzfeld studies that randomly sampled
from both dynamic and static target pools yielded an even
split of 165 sessions with each target type. As predicted,
sessions using dynamic targets yielded significantly more
hits than did sessions using static targets (37% vs. 27%),
Fisher’s exact p < .04.
Sender / receiver
pairing.
The
earlier
meta-analysis
found that studies in which participants were free to bring
in
friends
to
serve
as
senders
produced
significantly
higher hit rates than studies that used only laboratory-as-
signed senders. As noted, however, there is no record of
how many of the participants in the former studies actu-
ally did bring in friends.
Whatever the case, sender/receiver pairing was not a
significant
correlate
of
psi
performance
in
the
auto-
ganzfeld studies: The 198 sessions in which the sender
and receiver were
friends did not yield a
significantly
higher proportion of hits than did the 132
sessions
in
which they were not (34% vs. 29%), Fisher’s exact p = .34.
Correlations
between
receiver
characteristics and psi
performance. Most of the autoganzfeld participants were
strong believers in psi: On a 7-point scale, where “1” indi-
cates strong dieibelief and “7” indicates strong belief in psi,
the mean was 6.2 (SD = 1.03); only two participants rated
their belief in psi below the midpoint of the scale. In addi-
tion, 88% of the
participants reported personal
experi-
ences suggestive of psi and 80% had some training in
meditation or other techniques involving internal focus of
attention.
All of these appear to be important variables. The corre-
lation between belief in psi and psi performance is one of
the most consistent findings in the parapsychological
lit-
erature (Palmer, 1978). And within the autoganzfeld stud-
ies, successful performance of novice (first-time) partici-
pants is significantly predicted by reported personal
psi
experiences, involvement with meditation or other mental
disciplines, and high scores on the Feeling and Perception
factors of the Myers-Briggs Type Inventory (Honorton,
1992; Honorton & Schechter, 1987). This recipe for success
has
now
been
independently
replicated
in
another
laboratory (Broughton, Kanthamani, & Khilji, 1990).
The personality trait of extraversion is also associated
with better psi performance. A meta-analysis of 60 inde-
pendent studies with nearly 3,000
subjects revealed a
small but reliable positive correlation between extraver-
sion and psi performance—especially in studies that used
free-response
methods
of
the
kind
employed
in
the
ganzfeld experiments (Honorton, Ferrari, & Bern,
1992).
Across 14 free-response studies by 4 independent investi-
gators, the correlation for 612 subjects was .20 (z = 4.82, p
= 1.5x 10“6
). This correlation was replicated in the auto-
ganzfeld studies, where extraversion scores were available
for 221 of the 241 subjects: r = .18, t (219) = 2.67, p = .004,
one-tailed.
And finally, there is the strong psi performance of the
Juilliard students, discussed above, which
is consistent
with
other
studies
in
the
parapsychological
literature
BUggesting a relationship between successful psi perfor-
mance and creativity or artistic ability.
Discussion
Earlier in this article we quoted from the abstract of the
Hyman-Honorton communique “We agree that the final
verdict awaits the outcome of future experiments
con-
ducted by a broader range of investigators and according
to more stringent standards” (1986, p. 351).
We believe that the “stringent standards” requirement
has been met by the autoganzfeld studies. The results are
statistically significant and consistent with those in the
earlier database. The mean effect size is quite respectable
when compared with other controversial research areas of
human performance (Harris &
Rosenthal, 1988a). And,
there
are
reliable
relationships between
successful
psi
,
performance and conceptually relevant experimental and
subject variables—relationships that also replicate previ-
ous findings. Hyman has
also commented on the
auto-
ganzfeld studies:
Honorton’s experiments have produced intriguing results.
If...independent
laboratories
can
produce
simil ar
results
with the same relationships and with the same attention to
rigorous
methodology,
then
parapsychology may
indeed
have finally captured its elusive quarry.
( 1991, p. 392)
Issues of Replication
As Hyman’s comment implies, the autoganzfeld studies
by themselves cannot satisfy the requirement that repli-
cations be conducted by a “broader range of investigators.”
Accordingly, we hope the findings reported here
will be
sufficiently provocative to prompt others to try replicating
the psi ganzfeld effect.
We believe it is essential, however, that future studies
comply with the methodological, statistical, and reporting
standards set forth in the joint communique and achieved
by the autoganzfeld studies. It is not necessary for studies
to be as automated or as heavily instrumented as the au-
toganzfeld studies in order to satisfy the methodological
guidelines, but they are
still likely to be labor intensive
and potentially expensive.6
6As the closing of the autoganzfeld laboratory exemplifies, it is
also difficult to obtain funding for psi research. The traditional,
peer-refereed sources of funding familiar to psychologists have
almost never funded proposals for psi research. The widespread
skepticism of psychologists toward psi is almost certainly a con-
tributing factor.
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Statistical Power and Replication
Would-be replicators also need to be reminded of the
power requirements for replicating small effects. Although
many academic psychologists do not believe in psi, many
apparently do believe in miracles when it comes to repli-
cation. Tversky and Kahneman (1971) posed the following
problem to their colleagues at meetings of the Mathemati-
cal Psychology Group and the American Psychological As-
sociation:
Suppose you have run an experiment on 20 subjects and
have obtained a significant result which confirms your the-
ory (2 = 2.23, p < .05, two-tailed). You now have cause to run
an additional group of 10 subjects. What do you think the
probability is that the results will be significant, by a one-
tailed test, separately for this group? (p. 105)
The median estimate was .85, with nine out of ten re-
spondents giving an estimate greater than
.60. The cor-
rect answer is approximately .48.
As Rosenthal (1990) has warned: “Given the levels of
statistical power at which we normally operate, we have
no right to expect the proportion of significant results that
we typically do expect, even if in nature there
is a very
real and very important effect” (p. 16).
In
this regard,
it
is again instructive to consider the
medical study that found a highly significant effect of as-
pirin on the incidence of heart attacks. The study moni-
tored over 22,000 subjects. Had the investigators moni-
tored 3,000 subjects, they would have had less than an
even chance of finding a conventionally significant effect.
Such is life with small effect sizes.
Given its larger effect
size, the prospects for success-
fully replicating the psi ganzfeld effect are not quite so
daunting, but they are probably still grimmer than intu-
ition would suggest. If the true hit rate is in fact about
34% when 25% is expected by chance, then an experiment
with 30 trials (the mean for the 28 studies in the original
meta-analysis) has only about 1 chance in 6 of finding an
effect significant at the .05 level with a one-tailed test. A
50 trial experiment boosts that to about 1 in 3. One must
escalate to 100 trials in order to come close to the break
even point—where one has a 50-50 chance of finding a
statistically
significant
effect
(Utts,
1986).
(Recall
that
only 2 of the 11 autoganzfeld studies yielded results that
were
individually
significant
at
the
conventional
.05
level.) Those who require that a psi effect be statistically
significant every time before they will seriously entertain
the possibility that an effect really exists know not what
they ask.
Significance vs. Effect Size
But the preceding discussion is unduly pessimistic be-
cause it perpetuates the tradition of worshipping the sig-
nificance level. Regular readers of this journal are likely
to be familiar with recent arguments imploring behavioral
scientists to overcome
their
slavish dependence on the
significance level as the ultimate measure of virtue and to
focus more
of their
attention on
effect
sizes
instead:
“Surely, God loves the
.06 nearly as much
as the
.05”
(Rosnow &
Rosenthal,
1989,
p.
1277).
Accordingly, we
suggest that achieving a respectable
effect
size with
a
methodologically tight ganzfeld study would be a perfectly
welcome contribution to the replication effort—no matter
how untenurable the p level renders the investigator.
Career consequences aside, this suggestion may seem
quite
counterintuitive.
Again,
Tversky and Kahneman
(1971) provide an elegant demonstration. They asked sev-
eral of their colleagues to consider an investigator who
runs 15 subjects and obtains a significant t value of 2.46.
Another investigator attempts to duplicate the procedure
with the same number of subjects and obtains a result in
the same direction but with a nonsignificant value of t.
Tversky and Kahneman then asked their colleagues to in-
dicate the highest level of t in the replication Btudy they
would describe as a failure to replicate. The majority of
their colleagues regarded t = 1.70 as a failure to replicate.
But if the data from two such studies
(
= 2.46 and t =
1.70) were pooled, the t
for the combined data would be
about 3.00 (assuming equal variances):
Thus, we are faced with a paradoxical state of affairs,
in
which the same data that would increase our confidence in
the finding when viewed as part of the original study, shake
our confidence when viewed as an independent study,
(p.
108)
Such is the iron grip of the arbitrary .05. Pooling the
data, of course, is what meta-analysis is all about. Ac-
cordingly, we suggest that two or more laboratories could
collaborate in a ganzfeld replication effort by conducting
independent studies and then pooling them in meta-ana-
lytic fashion—what we might call real-time meta-analy-
sis. (Each investigator could then claim the pooled p
level for his or her own curriculum vitae.)
Maximizing Effect Size
Rather than buying or borrowing larger sample sizes,
those who seek to replicate the psi ganzfeld effect might
find it more intellectually satisfying to attempt to maxi-
mize the effect size by attending to the variables associ-
ated with successful outcomes. Thus researchers who wish
to enhance the chances of successful
replication should
use dynamic rather than static targets. Similarly we ad-
vise using participants with the characteristics we have
reported to be correlated with successful psi performance.
Random college sophomores enrolled in introductory psy-
chology do not constitute the optimal subject pool.
And finally, we urge, ganzfeld researchers to read care-
fully the detailed description of the warm social ambiance
that Honorton et al. (1990) sought to create in the auto-
ganzfeld laboratory. We believe that the
social climate
created in
psi experiments
is a
critical determinant of
their success or failure.
The Problem of “Other” Variables
11118 caveat about the social climate of the ganzfeld ex-
periment prompted one reviewer of this article to worry
that this provided “an escape clause” which weakens the
falsifiability of the psi hypothesis: “Until Bern and Hon-
orton
can
provide
operational
criteria
for
creating
a
warm social ambiance, the failure of an experiment with
otherwise adequate power can always be dismissed as
due to a lack of warmth.”
Alas, it’s true; we devoutly wish it were otherwise. But
the operation of unknown variables in moderating the
success of replications is a fact of life in all the sciences.
Consider, for example, an earlier article in this journal
by
Spence
(1964).
He
reviewed
studies
testing
the
straightforward derivation from Hullian learning theory
that
high
anxiety
subjects
should
condition
more
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strongly than low anxiety subjects. This hypothesis was
confirmed 94% of the time in Spence’s own laboratory at
the University of Iowa but only 63% of the time in labo-
ratories at other universities. In fact, Kimble and his as-
sociates at Duke and North Carolina obtained results in
the opposite direction in two out of three experiments.
In searching for a post hoc explanation, Spence noted
that “a deliberate attempt was made in the Iowa studies
to provide conditions in the laboratory that might elicit
some degree of emotionality. Thus, the experimenter was
instructed to be impersonal and quite formal
... and did
not try to put [subjects] at ease or allay any expressed
fears.” Moreover, he pointed out, his subjects sat in a
dental chair whereas Kimble’s subjects sat in a secretar-
ial chair. Spence even considered “the
possibility that
cultural backgrounds of southern and northern students
may lead to a 'difference in the manner in which they re-
spond to the different items in the [Manifest Anxiety]
scale.”
If this was the state of affairs in an area of research as
well established as classical conditioning, then the sug-
gestion that the social climate of the psi laboratory might
affect the outcome of ganzfeld experiments in ways not
yet completely understood should not be dismissed as a
devious attempt to provide an “escape clause” in case of
replication failure.
The best the original researcher can do is provide as
complete a description of the experimental conditions as
possible in an attempt to anticipate what some of the
relevant moderating variables might be. The detailed de-
scription
of the
autoganzfeld
procedures
provided by
Honorton et al. (1990) comes as close as current knowl-
edge permits in providing the “operational
criteria
for
creating a warm social ambiance.”
Theoretical Considerations
Up
to this point, we have confined our discussion
to
strictly empirical matters. We are sympathetic to the view
that one should establish the existence of a phenomenon,
anomalous or not, before attempting to explain it.
So let us suppose for the moment that it’s true. Let us
suppose that we have a genuine anomaly of information
transfer before us. How can it be understood or explained?
The Psychology ofPsi
In
attempting
to
understand
psi,
parapsychologists
have typically begun with the working assumption that,
whatever
its underlying mechanisms,
it should behave
like
other, more
familiar
psychological phenomena.
In
particular, they typically assume that target information
behaves like an external sensory stimulus that is encoded,
processed, and experienced in familiar information-pro-
cessing
ways.
Similarly,
individual
psi
performances
should covary with experimental and subject variables in
psychologically (sensible ways. These assumptions are em-
bodied in the model of psi that motivated the ganzfeld
studies in the first place.
The ganzfeld procedure. As noted in the introduction,
the ganzfeld procedure was designed to test a model in
which psi-mediated information
is conceptualized
as a
weak signal that is normally masked by internal somatic
and external sensory “noise.” Accordingly, any technique
that raises the aignal-to-noiee ratio should enhance a per-
son’s ability to detect the psi-mediated information. This
noise-reduction model of psi organizes a large and diverse
body of experimental results, particularly those demon-
strating the psi-conducive properties of altered states of
consciousness like meditation, hypnosis, dreaming, and, of
course, the ganzfeld itself (Rao & Palmer, 1987).
Alternative theories propose that the ganzfeld (and al-
tered states) may be psi-conducive because it lowers resis-
tance to accepting alien imagery, diminishes rational or
contextual constraints on the encoding or reporting of in-
formation, stimulates more divergent thinking, or even
just serves as a placebo-like ritual that participants per-
ceive
as being psi conducive
(Stanford,
1987). At
this
point, there are no data that would permit us to choose
among these alternatives, and the noise-reduction model
remains the most widely accepted.
The target. There are also a number of plausible hy-
potheses that attempt to account for the superiority of dy-
namic targets over static targets: Dynamic targets contain
more information, involve more sensory modalities, evoke
more of the receiver’s internal schemata, are more
life-
like, have a narrative structure, are more emotionally
evocative, and are
“richer” in
other, unspecified ways.
Several psi researchers have attempted to go beyond the
simple dynamic/static dichotomy to more refined or the-
ory-based definitions of a good target. Although these ef-
forts have
involved examining both
psychological and
physical properties of targets, there is not much progress
to report yet (Delanoy, 1990).
The receiver. Some of the subject characteristics asso-
ciated with good psi performance also appear to have psy-
chologically straightforward explanations. For example,
garden-variety motivational explanations seem sufficient
to account for the relatively consistent finding that those
who believe in psi perform significantly better than those
who do not. (Less straightforward, however, would be an
explanation for the frequent finding that nonbelievers ac-
tually
perform
significantly
worse
than
chance
(Broughton, 1991, p. 109).)
The superior psi performance of creative or artistically
gifted individuals—like the Juilliard students—may
re-
flect individual differences that parallel some of the hy-
pothesized effects of the ganzfeld, mentioned above: Ar-
tistically gifted individuals may be more receptive to alien
imagery, be better able to transcend rational or contextual
constraints on the encoding or reporting of information, or
be more divergent in their thinking. It has also been sug-
gested that both artistic and psi abilities might be rooted
in superior right-brain functioning.
The observed relationship between extraversion and
psi performance has been of theoretical interest for many
years. Eysenck (1966) reasoned that extraverts should
perform well in psi tasks because they are easily bored
and respond favorably to novel stimuli. In a setting like
the ganzfeld, extraverts may become “stimulus starved”
and thus be highly sensitive to any stimulation, including
weak incoming
psi information. In
contrast,
introverts
would be more inclined to entertain themselves with their
own thoughts and thus continue to mask psi information
despite the diminished sensory input. Eysenck also specu-
lated that psi might be a primitive form of perception an-
tedating cortical developments in the course of evolution,
and, hence, cortical arousal might suppress psi function-
ing. Because extraverts have a lower
level
of cortical
arousal than introverts, they should perform better in psi
tasks. (The evolutionary biology of psi is also discussed by
Broughton (1991, pp. 347-352).)
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