I downloaded the paper off Bem's site. Here is the write-up of the first experiment, which is also the one with the most pronounced result. It's just a couple of pages. Comments later if I have time.
Precognitive Approach and Avoidance
The presentiment studies provide evidence that our physiology can anticipate unpredictable
erotic or negative stimuli before they occur. Such anticipation would be evolutionarily
advantageous for reproduction and survival if the organism could act instrumentally to approach
erotic stimuli and avoid negative stimuli. The two experiments in this section were designed to
test whether individuals can do so.
Experiment 1: Precognitive Detection of Erotic Stimuli
As noted above, most of the earlier experiments in precognition explicitly challenged
participants to guess which one of several stimuli would be randomly selected after they
recorded their guess. In most of these experiments, participants were also given explicit trial-bytrial
feedback on their performance. This first experiment adopts that same traditional protocol,
using erotic pictures as explicit reinforcement for correct “precognitive” guesses.
Method
One hundred Cornell undergraduates, 50 women and 50 men, were recruited for this
experiment using the Psychology Department’s automated online sign-up system.1 They either
received one point of experimental credit in a psychology course offering that option or were
paid $5 for their participation. Both the recruiting announcement and the introductory
explanation given to participants upon entering the laboratory informed them that
this is an experiment that tests for ESP. It takes about 20 minutes and is run
completely by computer. First you will answer a couple of brief questions. Then,
on each trial of the experiment, pictures of two curtains will appear on the screen
side by side. One of them has a picture behind it; the other has a blank wall
1I set 100 as the minimum number of participants/sessions for each of the experiments reported in this
article because most effect sizes (d) reported in the psi literature range between 0.2 and 0.3. If d = 0.25
and N = 100, the power to detect an effect significant at .05 by a one-tailed, one-sample t test is .80
(Cohen, 1988).
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behind it. Your task is to click on the curtain that you feel has the picture behind
it. The curtain will then open, permitting you to see if you selected the correct
curtain. There will be 36 trials in all.
Several of the pictures contain explicit erotic images (e.g., couples engaged in
nonviolent but explicit consensual sexual acts). If you object to seeing such
images, you should not participate in this experiment.
The participant then signed a consent form and was seated in front of the computer. After
responding to two individual-difference items (discussed below), the participant had a 3-min
relaxation period during which the screen displayed a slowly moving Hubble photograph of the
starry sky while peaceful new-age music played through stereo speakers. The 36 trials began
immediately after the relaxation period.
Stimuli. Most of the pictures used in this experiment were selected from the International
Affective Picture System (IAPS; Lang & Greenwald, 1993), a set of 820 digitized photographs
that have been rated on 9-point scales for valence and arousal by both male and female raters.
This is the same source of pictures used in most presentiment studies. Each session of the
experiment included both erotic and nonerotic pictures randomly intermixed, and the main psi
hypothesis was that participants would be able to identify the position of the hidden erotic
picture significantly more often than chance (50%).
The hit rate on erotic trials can also be compared with the hit rates on the nonerotic trials to
test whether there is something unique about erotic content in addition to its positive valence and
high arousal value. For this purpose, 40 of the sessions comprised 12 trials using erotic pictures,
12 trials using negative pictures, and 12 trials using neutral pictures. The sequencing of the
pictures and their left/right positions were randomly determined by the programming language’s
internal random function. The remaining 60 sessions comprised 18 trials using erotic pictures
and 18 trials using nonerotic positive pictures with both high and low arousal ratings. These
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Feeling the Future 8
included eight pictures featuring couples in romantic but nonerotic situations (e.g., a romantic
kiss, a bride and groom at their wedding). The sequencing of the pictures on these trials was
randomly determined by a randomizing algorithm devised by Marsaglia (1997), and their
left/right target positions were determined by an Araneus Alea I hardware-based random number
generator. (The rationale for using different randomizing procedures is discussed in detail
below.)
Although it is always desirable to have as many trials as possible in an experiment, there
are practical constraints limiting the number of critical trials that can be included in this and
several others experiments reported in this article. In particular, on all the experiments using
highly arousing erotic or negative stimuli a relatively large number of nonarousing trials must be
included to permit the participant’s arousal level to “settle down” between critical trials. This
requires including many trials that do not contribute directly to the effect being tested.
In our first retroactive experiment (Experiments 5, described below), women showed psi
effects to highly arousing stimuli but men did not. Because this appeared to have arisen from
men’s lower arousal to such stimuli, we introduced different erotic and negative pictures for men
and women in subsequent studies, including this one, using stronger and more explicit images
from Internet sites for the men. We also provided two additional sets of erotic pictures so that
men could choose the option of seeing male–male erotic images and women could choose the
option of seeing female–female erotic images.2
From the participants’ point of view, this procedure appears to test for clairvoyance. That
is, they were told that a picture was hidden behind one of the curtains and their challenge was to
guess correctly which curtain concealed the picture. In fact, however, neither the picture itself
2 In describing the experiments throughout this article, I have used the plural pronouns “we” and “our” to
refer collectively to myself and my research team.
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Feeling the Future 9
nor its left/right position was determined until after the participant recorded his or her guess,
making the procedure a test of detecting a future event, that is, a test of precognition.
Results and Discussion
Across all 100 sessions, participants correctly identified the future position of the erotic
pictures significantly more frequently than the 50% hit rate expected by chance: 53.1%, t(99) =
2.51, p = .01, d = 0.25.3 In contrast, their hit rate on the nonerotic pictures did not differ
significantly from chance: 49.8%, t(99) = -0.15, p = .56. This was true across all types of
nonerotic pictures: neutral pictures, 49.6%; negative pictures, 51.3%; positive pictures, 49.4%;
and romantic but nonerotic pictures, 50.2%. (All t values < 1.) The difference between erotic and
nonerotic trials was itself significant, tdiff(99) = 1.85, p = .031, d = 0.19. Because erotic and
nonerotic trials were randomly interspersed in the trial sequence, this significant difference also
serves to rule out the possibility that the significant hit rate on erotic pictures was an artifact of
inadequate randomization of their left/right positions.
Because there are distribution assumptions underlying t tests, the significance levels of
most of the positive psi results reported in this article were also calculated with nonparametric
tests. In this experiment, the hit rates on erotic trials were also analyzed with a binomial test on
the overall proportion of hits across all trials and sessions, tested against a null of .5. This is
analogous to analyzing a set of coin flips without regard to who or how many are doing the
flipping. It is legitimate here because the target is randomly selected on each trial and hence the
trials are statistically independent, even within a single session. Across all 100 sessions, the
53.1% hit rate is also significant by a binomial test, z = 2.30, p = .011.
3 Unless otherwise indicated, all significance levels reported in this article are based on one-tailed tests
and d is used as the index of effect size.
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Individual Differences. There were no significant sex differences in the present
experiment. Over the years, however, the trait of extraversion has been frequently reported as a
correlate of psi, with extraverts achieving higher psi scores than introverts. A meta-analysis of 60
independent experiments published between 1945 and 1983, involving several kinds of psi tasks,
revealed a small but reliable correlation between extraversion and psi performance, r = .09, z =
4.63, p = .000004 (Honorton, Ferrari, & Bem, 1992). The correlation was observed again in a
later set of telepathy studies conducted in Honorton’s own laboratory, r = .18, t(216) = 2.67, p =
.004 (Bem & Honorton, 1994).
The component of extraversion that underlies this correlation appears to be the extravert’s
susceptibility to boredom and a tendency to seek out stimulation. Eysenck attributed the positive
correlation between extraversion and psi to the fact that extraverts “are more susceptible to
monotony…[and] respond more favourably to novel stimuli” (1966, p. 59). Sensation seeking is
one of the 6 facets of extraversion on the Revised NEO Personality Inventory (Costa & McCrae,
1992), and Zuckerman’s Sensation Seeking Scale (1974), which contains a subscale of Boredom
Susceptibility, is significantly correlated with overall extraversion (r = .47, p < .01; Farley &
Farley, 1967).
To assess stimulus seeking as a correlate of psi performance in our experiments, I
constructed a scale comprising the following two statements: “I am easily bored” and “I often
enjoy seeing movies I’ve seen before” (reverse scored). Responses were recorded on 5-point
scales that ranged from Very Untrue to Very True and averaged into a single score ranging from
1 to 5.
In the present experiment, the correlation between stimulus seeking and psi performance
was .18 (p = .035). This significant correlation is reflected in the enhanced psi scores of those
scoring above the midpoint on the 5-point stimulus-seeking scale: They correctly identified the
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future position of the picture on 57.6% of the erotic trials, t(41) = 4.57, p = .00002, d = 0.71,
exact binomial p = .00008. The difference between their erotic and nonerotic hit rates was itself
significant, tdiff(41) = 3.23, p = .001, d = 0.50, with 71% of participants achieving higher hit rates
on erotic trials than on nonerotic trials (exact binomial p = .003). Their psi scores on nonerotic
trials did not exceed chance, 49.9%, t(41) = -0.08, p = .53. Finally, participants low in stimulus
seeking did not score significantly above chance on either erotic or nonerotic trials 49.9%, t(57)
= -0.06 and 49.9%, t(57) = -0.13, respectively.
But is it Precognition? The Role of Random Number Generators. For most
psychological experiments, a random number table or the random function built into most
programming languages provides an adequate tool for randomly assigning participants to
conditions or sequencing stimulus presentations. For both methodological and conceptual
reasons, however, psi researchers have paid much closer attention to issues of randomization.
At the methodological level, the problem is that the random functions included in most
computer languages are not very good in that they fail one or more of the mathematical tests
used to assess the randomness of a sequence of numbers (L’Ecuyer, 2001), such as Marsaglia’s
rigorous Diehard Battery of Tests of Randomness (1995). Such random functions are sometimes
called pseudo random number generators (PRNGs) because they use a mathematical algorithm to
generate each subsequent number from the previous number, and the sequence of numbers is
random only in the sense that it satisfies (or should satisfy) certain mathematical tests of
randomness. It is not random in the sense of being indeterminate because once the initial starting
number (the seed) is set, all future numbers in the sequence are fully determined.
In contrast, a hardware-based or “true” RNG is based on a physical process, such as
radioactive decay ...
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