Blackmore and Rose (1997) suggested a link between
psi and a person’s tendency to confuse reality and imagination, and
reported an experiment that examined two hypotheses. The first was that
people may misinterpret their own imagination as reality; leading them
to conclude that a psychic phenomenon has occurred when in fact it has
not. In this case we would expect believers in the paranormal to be more
likely to confuse reality and imagination. The second proposed that the
confusion between reality and imagination is itself psi-conducive - as
though psi can somehow sneak into the uncertainty gap.
Subjects were shown slides, half of which showed
common objects with labels underneath, and the others just labels. For
the latter they were asked to imagine the objects named. Some were shown
once and some three times. Over the following two weeks, subjects were
asked to describe, draw and answer questions about all the objects. By
the end of the experiment we expected that many of them would have been
confused into thinking that they actually saw some objects that, in fact,
they had only imagined (i.e. false memories).
Psi targets were pictures of half of the imagined
objects (randomly selected for each subject) and were concealed in envelopes
during the first session. The analysis compared the number of false memories
on targets (hits) with the number on non-targets (misses) for each subject.
Belief was measured using the Revised Paranormal Belief Scale (Tobacyk,
1988) and scores were correlated with the number of false memories for
each subject.
The technique used in Blackmore and Rose (1997)
successfully induced false memories in many subjects. That is they said
that they had seen an object when they had actually imagined it. 8 subjects
made a total of 12 errors of this kind. A significant psi effect was found.
That is, there were more false memories for target objects (ESP hits)
than for non-target objects (ESP misses) (t=2.25, 32df, p=0.032, 2-tailed).
Using Cohen’s d (Rosenthal, 1984), the effect size was 0.80. We predicted
a correlation between the number of false memories and PBS score. However,
no such correlation was found (rs = 0.069, n=32, p=0.70). Neither was
there any correlation between total errors (regardless of type) and BPS
score (rs = 0.046, n=33, p=0.80).
In this research brief we report two further
experiments carried out using the same technique. The first is an exact
replication of the original experiment designed to see whether the apparent
psi effect could be repeated. The second used a modified design in an
attempt to increase the number of false memories obtained.
In the first experiment 26 psychology students
took part, and 13 subjects made a total of only 19 false memory errors.
There were 10 hits and 9 misses, which is non-significant (t=0.25, 12df,
p=0.808, 2-tailed). No correlation was found between the number of false
memories and BPS score (rs = -0.134, n=25, p=0.53).
Problems with this experiment included the low
numbers of subjects completing all phases and the low numbers of false
memories produced. We completed a further study (not reported here) in
which subjects were tested individually with the stimuli presented by
computer. We measured the time they took to draw and describe the objects
and the time taken to recall which objects they had seen in the final
session. From the results of all these experiments we designed the final
classroom study as follows.
Time limits previously imposed on the tests were
removed. Subjects’ data were included if they had attended only one
of the intermediate sessions and the time between the first and last session
was increased from three weeks to two months.
82 psychology students took part. The number
of false memories improved; 60 subjects made a total of 148 false memory
errors. There were 73 false memories for target objects (hits) and 75
false memories for non-target objects (misses); a non-significant difference
(t=-0.22, 81df, p=0.829). Once again, no correlation between PBS score
and false memory was found (rs = -0.178, n=81, p=0.11).
The modified classroom design used in this experiment
appears an ethical and effective method for producing false memories.
The failure to replicate the original psi result was disappointing, and
having reviewed the possible causes the most parsimonius explanation for
the original result appears to be chance. Our second hypothesis, that
believers in the paranormal might make more false memory errors, was not
confirmed in any of the experiments. Whilst this may, in part, be due
to the well documented weaknesses of the Tobacyk (1988) scale, the results
suggest that there is no relationship. However, these findings do not
rule out the possibility that believers in the paranormal may be more
likely to have false memory for ostensibly paranormal events.
With thanks to the Perrott-Warrick fund for their financial
assistance to this research, and to Kerry Grey who assisted with running
one of the experiments.
