Citation

A repeated finding in the parapsychology literature is that attitudes prior to testing can influence performance on tests of ESP. This is true of both the attitudes participants bring to the situation and attitudes experimentally induced both prior to and during testing. The aim of the current studies was to compare the effects of manipulating expectation before and also during a test of ESP. Experience was manipulated in two ways: through the administration of a placebo which participants were told had previously been found to increase ESP abilities, and by providing feedback that was either an accurate or a falsely positive indication of performance. In both studies an interaction was found between placebo and false feedback, and post hoc tests revealed that the placebo affected performance only when coupled with falsely positive feedback. In Experiment 2, false feedback was shown to influence negatively the performance of those with a prior belief in parapsychological phenomena. The results are discussed in terms of the additive effects of both manipulations on efficacy expectations.