Abstract

Examined a database of studies published in the main parapsychology journals from 1935-1997 that compared outcomes of precognition and clairvoyance trials under relatively similar experimental conditions. The studies were selected and coded according to specific criteria. Both the precognition and clairvoyance studies had significant cumulated overall effect, but there was no evidence to suggest that clairvoyance worked better than precognition. No significant correlations were found between the presence of procedural safeguards and effect size, suggesting that methodological problems had not played any strong and obvious role in the overall effects. Results suggest that theories about parapsychological phenomena and future experimental designs should not rest on assumptions that require a difference in precognition and clairvoyance effect sizes.