5.2 Ganzfeld Results from Four Laboratories
In publishing the ganzfeld results from PRL, Bem and Honorton (1994) excluded one of the studies from the general analysis for methodological reasons, and found that the remaining studies showed 106 hits out of 329 sessions, for a hit rate of 32.2 percent when 25 percent was expected by chance. The corresponding p-value was .002. As mentioned earlier, the hallmark of science is replication. This result has now been replicated by three additional laboratories.
Bierman (1995) reported four series of experiments conducted at the University of Amsterdam. Overall, there were 124 sessions and 46 hits, for a hit rate of 37 percent. The hit rates for the four individual experiments were 34.3 percent, 37.5 percent, 40 percent and 36.1 percent, so the results are consistent across his four experiments.
Morris, Dalton, Delanoy and Watt (1995) reported results of 97 sessions conducted at the University of Edinburgh in which there were 32 successes, for a hit rate of 33 percent. They conducted approximately equal numbers of sessions under each of three conditions. In one condition there was a known sender, and in the other two conditions it was randomly determined at the last minute (and unknown to the receiver) that there would either be a sender or not. Hit rates were 34 percent when there was a known sender and when there was no sender, and 28 percent when there was a sender but the receiver did not know whether or not there would be. They did discover post hoc that one experimenter was more successful than the other two at achieving successful sessions, but the result was not beyond what would be expected by chance as a post hoc observation.
Broughton and Alexander (1995) reported results from 100 sessions at the Institute for Parapsychology in North Carolina. They too found a similar hit rate, with 33 hits out of 100 sessions, or 33 percent hits.
Results from the original ganzfeld work and these three replications are summarized in Table 3, along with the SRI and SAIC remote viewing results. The effect sizes for the ganzfeld replications are based on Cohen's h, which is similar in type to the effect size used for the remote viewing data. Both effect sizes measure the number of standard deviations the results fall above chance, using the standard deviation for a single session.
5.3 Conclusions about External Replication
The results shown in Table 3 show that remote viewing has been conceptually replicated across a number of laboratories, by various experimenters and in different cultures. This is a robust effect that, were it not in such an unusual domain, would no longer be questioned by science as a real phenomenon. It is unlikely that methodological problems could account for the remarkable consistency of results shown in Table 3.