The Consortium Replication, and the Funnel Plot

Two pieces of evidence closed the case for most readers outside the laboratory. The first was the PortREG consortium experiment conducted around 2000, in which PEAR joined research groups at Giessen and at Freiburg to run one agreed protocol on PEAR's own hardware and software at all three sites. The point of the design was to remove the objection that only one laboratory could produce the effect. The outcome was trends in the expected direction at each site, none of them statistically significant, and a combined result that did not support the original claim.

Jahn and Dunne argued at length that the shared protocol had constrained the operators in ways the original work had not, which is a defensible reading and also the reading that makes the hypothesis unfalsifiable. The second was the 2006 meta-analysis by Bösch, Steinkamp and Boller in Psychological Bulletin, covering the whole random generator literature. It found a small significant overall effect and, alongside it, a strong inverse relation between effect size and sample size, meaning the largest studies came closest to chance. That asymmetry is the standard fingerprint of publication bias, and the authors concluded the literature was better explained by selective reporting. Proponents contest the correction, not the asymmetry.