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Psychological Bulletin
1994, VoU
11 5, No. 1,4-18
Copyright
1 994 by the American Psychological Assodalion. Iiw.
Does Psi Exist? Replicable Evidence for an Anomalous Process of
Information Transfer
Daryl J. Bern and Charles Honorton
Most academic psychologists do not yet accept the existence of psi, anomalous processes of informa-
tion or energy transfer (such as telepathy or other forms of extrasensory perception)
t
at are cur
rently unexplained in terms of known physical or biological mechanisms. We believe t
at t
e rep
t
cation rates and effect sizes achieved by one particular experimental method, the ganzfeld procedure,
are now sufficient to warrant bringing this body of data to the attention of the wider psyc o ogica
community. Competing meta-analyses of the ganzfeld database are reviewed,
1 by R. Hyman ( 1985),
a skeptical critic of psi research, and the other by C. Honorton (1985), a parapsychology and major
contributor to the ganzfeld database. Next the results of
1 new ganzfeld studies that comply with
guidelines jointly authored by R. Hyman and C. Honorton (1986) are summarized. Finally, issues
of replication and theoretical explanation are discussed.
The term psi denotes anomalous processes of information or
energy transfer, processes such as telepathy or other forms of
extrasensory
perception
that
are
currently
unexplained
in
terms ofknown physical or biological mechanisms. The term is
purely descriptive: It neither implies that such anomalous phe-
nomena are paranormal nor connotes anything about their un-
derlying mechanisms.
Does psi exist? Most academic psychologists don’t think so.
A survey of more than 1,100 college professors in the United
States found that 55% of natural scientists, 66% of social scien-
tists (excluding psychologists), and 77% ofacademics in the arts,
humanities, and education believed that ESP is either an estab-
lished fact or a likely possibility. The comparable figure for psy-
Daryl J. Bern, Department of Psychology, Cornell University; Charles
Honorton, Department of Psychology, University of Edinburgh, Edin-
burgh, Scotland.
IQQ ,
Sadly, Charles Honorton died of a heart attack on November 4,
1 992,
9 days before this article was accepted for publication. He was 46. Para-
psychology has lost one of its most valued contributors.
I have lost a
valued friend.
,
This collaboration had its origins ina 1983 visitlmade to Honorton s
Psychophysical Research Laboratories (PRL) in Princeton, New Jersey,
as one of several outside consultants brought in to examine the design
and implementation of the experimental protocols.
Preparation ofthis article was supported, in part, by grants to Charles
Honorton from the American Society for Psychical Research and the
Parapsychology Foundation, both of New York City. The work at PRL
summarized in the second half of this article was supported by
he
James S. McDonnell Foundation of St. Louis, Missouri, and by th
JohnE. Fetzer Foundation of Kalamazoo, Michigan.
Helpful comments on drafts of this article were received from Debo-
rah Delanoy, Edwin May, Donald McCarthy, Robert Morns
John
Palmer, Robert Rosenthal, Lee Ross, Jessica Utts, Philip Zimbardo, and
two anonymous reviewers.
.
.
Correspondence concerning this article should be addressed to Daryl
J. Bern, Department of Psychology, Uns Hall, Come
I Un 'v™‘^
[
aca, New York
14853. Electronic mail may be sent to d.bemQcor
nell.edu.
chologists was only 34%. Moreover, an equal number of psy-
chologists declared ESP to be an impossibility, a view expressed
by only 2% of all other respondents (Wagner & Monnet, 1979).
We psychologists are probably more skeptical about psi for
several reasons. First, we believe that extraordinary claims re-
quire extraordinary proof. And although our colleagues from
other disciplines would probably agree with this dictum, we are
more likely to be familiar with the methodological and statisti-
cal requirements for sustaining such claims, as well as with pre-
vious claims that failed cither to meet those requirements or
to survive the test of successful replication. Even for ordinary
claims, our conventional
statistical
criteria are conservative.
The sacred p - .05 threshold is a constant reminder that it is far
more sinful to assert that an effect exists when it does not (the
Type
I error) than to assert that an effect does not exist when it
does (the Type II error).
Second, most of us distinguish sharply between phenomena
whose explanations are merely obscure or controversial (e.g.,
hypnosis) and phenomena such as psi that appear to fall outside
our current explanatory framework altogether. (Some would
characterize this as the difference between the unexplained and
the inexplicable.) In contrast, many laypersons treat all exotic
psychological
phenomena
as
epistemologically
equivalent;
many even consider dcjl vu to be a psychic phenomenon. The
blurring of this critical distinction is aided and abetted by the
mass media, “new age" books and mind-power courses, and
"psychic" entertainers who present both genuine hypnosis and
fake “mind reading" in the course of a single performance. Ac-
cordingly. most lay persons would not have to revise their con-
ceptual model of reality as radically as wc would in order to
assimilate the existence of psi. For us, psi
is simply more ex-
traordinary.
Finally, research in cognitive and social psychology has sensi-
tized us to the errors and biases that plague intuitive attempts
to draw valid inferences from the data of everyday experience
(Gtlovich. 1991
. Nisbetl A Ross. !980;Tversky & Kahneman,
1971). Thu leads us to gr»c virtually no probative weight to an-
ecdotal or journalistic rrporU of psi, the main source cited by
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ANOMALOUS INFORMATION TRANSFER
academic colleagues as evidence for their beliefs about psi
agner & Monnet, 1979).
ronically, however, psychologists are probably not more fa-
liar than others with recent experimental research on psi.
Ice most psychological research, parapsychological research is
orted primarily in specialized journals; unlike most psycho-
ical research, however, contemporary parapsychological re-
rch is not usually reviewed or summarized in psychology’s
xtbooks, handbooks, or mainstream journals. For example,
ly
1 of 64 introductory psychology textbooks recently sur-
ged even mentions the experimental procedure reviewed in
is article, a procedure that has been in widespread use since
c early 1970s (Roig, Icochea, & Cuzzucoli, 1991). Other sec-
ndary sources for nonspecialists are frequently inaccurate in
heir descriptions of parapsychological research. (For discus-
ions of this problem, see Child, 1985, and Palmer, Honorton,
Utts, 1989.)
This situation may be changing. Discussions of modern psi
escarch have recently appeared in a widely used introductory
extbook (Atkinson, Atkinson, Smith, & Bern, 1990, 1993), two
nainstream psychology journals (Child, 1985; Rao & Palmer,
1987), and a scholarly but accessible book for nonspecialists
Broughton, 1991). The purpose of the present article is to sup-
plement these broader treatments with a more detailed, meta-
malytic presentation of evidence issuing from a single experi-
mental method: the ganzfeld procedure. We believe that the
•eplication rates and effect sizes achieved with this procedure
ire now sufficient to warrant bringing this body of data to the
mention of the wider psychological community.
The Ganzfeld Procedure
By the 1960s, a number of parapsychologists had become dis-
satisfied with the familiar ESP testing methods pioneered by
J. B. Rhine at Duke University in the 1930s. In particular, they
believed that the repetitive forced-choice procedure in which a
subject repeatedly attempts to select the correct “target’ sym-
bol from a set of fixed alternatives failed to capture the circum-
stances that characterize reported instances of psi in everyday
life.
Historically, psi has often been associated with meditation,
hypnosis, dreaming, and other naturally occurring or deliber-
ately induced altered states of consciousness. For example, the
view that psi phenomena can occur during meditation
is ex-
pressed in most classical texts on meditative techniques; the be-
lief that hypnosis is a psi-conducive state dates all the way back
to the days of early mesmerism (Dingwall,
1968); and cross-
cultural surveys indicate that most reported “real-life” psi ex-
periences are mediated through dreams (Green,
1 960; Prasad
& Stevenson, 1968; L. E. Rhine, 1962; Sannwald, 1959).
There are now reports of experimental evidence consistent
with these anecdotal observations. For example, several labora-
tory investigators have reported that meditation facilitates psi
performance (Honorton, 1977). A meta-analysis of 25 experi-
ments on hypnosis and psi conducted between 1945 and 1981
in
10 different laboratories suggests that hypnotic induction
may also
facilitate
psi performance
(Schechter,
1984). And
dream-mediated psi was reported in a series of experiments
conducted at Maimonides Medical Center in New York and
published between
1966
and
1972
(Child,
1985;
Ullman,
Krippner, & Vaughan, 1973).
In the Maimonides dream studies, two subjects—a “receiver’
and a “sender”—spent the night in a sleep laboratory. The re-
ceiver’s brain waves and eye movements were monitored as he
or she slept in an isolated room. When the receiver entered a
period of REM sleep, the experimenter pressed a buzzer that
signaled the sender—under the supervision of a second experi-
menter—to begin a sending period. The sender would then con-
centrate on a randomly chosen picture (the “target”) with the
goal of influencing the content of the receiver’s dream.
Toward the end of the REM period, the receiver was awak-
ened and asked to describe any dream just experienced. This
procedure was repeated throughout the night with the same
target. A transcription of the receiver’s dream reports was given
to outside judges who blindly rated the similarity of the night’s
dreams to several pictures, including the target. In some studies,
similarity ratings were also obtained from the receivers them-
selves. Across several variations of the procedure, dreams were
judged to be significantly more similar to the target pictures
than to the control pictures in the judging sets (failures to repli-
cate the Maimonides results were also reviewed by Child, 1985).
These several lines of evidence suggested a working model of
psi in which psi-mediated information
is conceptualized as a
weak signal that is normally masked by internal somatic and
external sensory “noise.” By reducing ordinary sensory input,
these diverse psi-conducive states are presumed to raise the sig-
nal-to-noise ratio, thereby enhancing a person’s ability to detect
the psi-mediated information (Honorton, 1969, 1977). To test
the hypothesis that a reduction of sensory input itself facilitates
psi performance, investigators turned to the ganzfeld procedure
(Braud, Wood, & Braud, 1975; Honorton & Harper, 1974; Par-
ker, 1975), a procedure originally introduced into experimental
psychology during the 1930s to test propositions derived from
gestalt theory (Avant, 1965; Metzger, 1930).
Like the dream studies, the psi ganzfeld procedure has most
often been used to test for telepathic communication between a
sender and a receiver. The receiver is placed in a reclining chair
in an acoustically isolated room. Translucent ping-pong ball
halves are taped over the eyes and headphones are placed over
the ears; a red floodlight directed toward the eyes produces an
undifferentiated visual field, and white noise played through the
headphones produces an analogous auditory field. It is this ho-
mogeneous perceptual environment that is called the Ganzfeld
(“total field”). To reduce internal somatic “noise,” the receiver
typically also undergoes a series of progressive relaxation exer-
cises at the beginning of the ganzfeld period.
The sender is sequestered in a separate acoustically isolated
room, and a visual stimulus (art print, photograph, or brief vid-
eotaped sequence)
is randomly selected from a large pool of
such stimuli to serve as the target for the session. While the
sender concentrates on the target, the receiver provides a con-
tinuous verbal report of his or her ongoing imagery and menta-
tion, usually for about 30 minutes. At the completion of the
ganzfeld period, the receiver is presented with several stimuli
(usually four) and, without knowing which stimulus was the
target, is asked to rate the degree to which each matches the
imagery and mentation experienced during the ganzfeld period.
Ifthe receiver assigns the highest rating to the target stimulus, it
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