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In 2011, one of the authors (DJB) published a report of nine experiments in the Journal of Personality and Social Psychology purporting to demonstrate that an individual's cognitive and affective responses can be influenced by randomly selected stimulus events that do not occur until after his or her responses have already been made and recorded, a generalized variant of the phenomenon traditionally denoted by the term precognition. To encourage replications, all materials needed to conduct them were made available on request. We here report a meta-analysis of 90 experiments from 33 laboratories in 14 countries which yielded an overall effect greater than 6 sigma, z = 6.40, p = 1.2 × 10 (-10 ) with an effect size (Hedges' g) of 0.09. A Bayesian analysis yielded a Bayes Factor of 1.4 × 10 (9), greatly exceeding the criterion value of 100 for "decisive evidence" in support of the experimental hypothesis. When DJB's original experiments are excluded, the combined effect size for replications by independent investigators is 0.06, z = 4.16, p = 1.1 × 10 (-5), and the BF value is 3,853, again exceeding the criterion for "decisive evidence." The number of potentially unretrieved experiments required to reduce the overall effect size of the complete database to a trivial value of 0.01 is 544, and seven of eight additional statistical tests support the conclusion that the database is not significantly compromised by either selection bias or by " p-hacking"-the selective suppression of findings or analyses that failed to yield statistical significance. P-curve analysis, a recently introduced statistical technique, estimates the true effect size of our database to be 0.20, virtually identical to the effect size of DJB's original experiments (0.22) and the closely related "presentiment" experiments (0.21). We discuss the controversial status of precognition and other anomalous effects collectively known as psi.

In 2011, one of the authors (DJB) published a report of nine experiments in the Journal of Personality and Social Psychology purporting to demonstrate that an individual’s cognitive and affective responses can be influenced by randomly selected stimulus events that do not occur until after his or her responses have already been made and recorded, a generalized variant of the phenomenon traditionally denoted by the term precognition. To encourage replications, all materials needed to conduct them were made available on request. We here report a meta-analysis of 90 experiments from 33 laboratories in 14 countries which yielded an overall effect greater than 6 sigma, z = 6.40, p = 1.2 × 10-10  with an effect size (Hedges’ g) of 0.09. A Bayesian analysis yielded a Bayes Factor of 1.4 × 109, greatly exceeding the criterion value of 100 for “decisive evidence” in support of the experimental hypothesis. When DJB’s original experiments are excluded, the combined effect size for replications by independent investigators is 0.06, z = 4.16, p = 1.1 × 10-5, and the BF value is 3,853, again exceeding the criterion for “decisive evidence.” The number of potentially unretrieved experiments required to reduce the overall effect size of the complete database to a trivial value of 0.01 is 544, and seven of eight additional statistical tests support the conclusion that the database is not significantly compromised by either selection bias or by “p-hacking”—the selective suppression of findings or analyses that failed to yield statistical significance. P-curve analysis, a recently introduced statistical technique, estimates the true effect size of our database to be 0.20, virtually identical to the effect size of DJB’s original experiments (0.22) and the closely related “presentiment” experiments (0.21). We discuss the controversial status of precognition and other anomalous effects collectively known as psi.

Two experiments involving an international collaboration of experimenters sought to replicate and extend a previously published psi experiment on precognition by Daryl Bem that has been the focus of extensive research. The experiment reverses the usual cause–effect sequence of a standard psychology experiment using priming and reaction times. The preregistered confirmatory hypothesis is that response times to incongruent stimuli will be longer than response times to congruent stimuli even though the prime has not yet appeared when the participant records their judgments. The confirmatory hypothesis for Experiment 1 was not supported. Exploratory analyses indicated that those participants who completed the English-language version rather than a translation showed a significant effect, as was the case in the original study; no significant departure from chance was found in data involving non-English translations. Experiment 2 sought to enhance the predicted effect by having each participant read either a pro-psi or an anti-psi statement at the beginning of the experiment to test the pre-recorded hypothesis that a pro-psi statement would produce a larger effect than an anti-psi statement. The results did not support the primary psi hypothesis and there was no effect in the English-language sample. However, there was mixed support for the effect of the psi statement on performance; those participants who received the pro-psi statement had a greater psi score than those who received the anti-psi statement. As in the original experiment, neither the experimenters’ nor participants’ beliefs were significantly associated with the dependent measure. In sum, the pre-registered confirmatory hypotheses were not supported. The importance of the personality variable Sensation Seeking, a component of extraversion, as a correlate of psi performance is discussed as are the challenges and implications for international collaborations and replication in controversial science. Keywords: priming; expectancy effect; retrocausation; consciousness; sociology; precognition; psi; replication           Two experiments involving an international collaboration of experimenters sought to replicate and extend a previously published psi experiment on precognition by Daryl Bem that has been the focus of extensive research. The experiment reverses the usual cause-effect sequence of a standard psychology experiment using priming and reaction times. The preregistered confirmatory hypothesis is that response times to incongruent stimuli will be longer than response times to congruent stimuli even though the prime has not yet appeared when the participant records his or her judgments. The confirmatory hypothesis for Study 1 was not supported. Exploratory analyses indicated that those participants who completed the English-language version rather than a translation showed a significant effect, as was the case in the original study; no significant departure from chance was found in data involving non-English translations. Study 2 sought to enhance the predicted effect by having each participant read either a pro-psi or an anti-psi statement at the beginning of the experiment to test the pre-recorded hypothesis that a pro-psi statement would produce a larger effect than an anti-psi statement. The results did not support the primary psi hypothesis and there was no observed association between belief and experience of ESP and psi outcome. However, there was mixed support for the effect of the psi statement on performance; those participants who received the pro-psi statement had a greater psi score than those who received anti-psi statement. As in the original experiment, neither the experimenters’ nor participants’ beliefs or expectations were significantly correlated with the dependent measure. In sum, the pre-registered confirmatory hypotheses were not supported. The importance of the personality variable Sensation Seeking, a component of extraversion, as a correlate of psi performance is discussed as are the challenges and implications for international collaborations and replication in controversial science.  

Previous studies have shown that the choice reaction time to a positive or negatively valenced photo can be influenced by following positive or negative words. Congruent photo-word pairs led to shorter reaction times than incongruent pairs. Since the potentially influencing word appears after the button is pressed, this effect has been described as a retroactive psi effect (Bem, 2011, Exp. 4). The present article reports on two studies that replicated the original English retroactive priming task using German words. Two new analysis methods are applied by (a) assessing whether the influence of a classic anterograde priming effect is detectable, which is not and (b) controlling in Study 2 for potential false-positive effects by utilizing a specially designed sham control task. By applying confirmatory analyses criteria, the anomalous cognition hypothesis concerning a positive psi effect is rejected in both studies. Exploratory post hoc analysis shows a significant positive retroactive priming effect in Study 1 for men only and an overall weak significant negative priming effect in Study 2. We discuss these ambivalent findings as typical anomalous result patterns in experimental parapsychology. Through these results, both those who are sceptic of anomalous cognition and those who believe in it can find confirmation of their assumptions.

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