While being aware of the necessity for control in parapsychological experiments, we make a plea for 'sloppy' conditions, especially in those cases where the sterility of the laboratory results in the loss of environmental factors that may facilitate gifted subjects to produce strong effects.
In this study the manipulation of a theory-relevant variable (i.c. feedback) served as a control against cheating. Significant above chance scoring was obtained in a binary color guessing task if the delayed feedback was correct (scoring rate = 58%; p < 0.02) while in the no-feedback and incorrect delayed feedback conditions scoring was at chance level (48.5%). In the direct feedback condition no (theory based) control was implemented and the scoring rate was at 64% (p < 0.00001).
The results are interpreted as supporting the Observational model of psi phenomena. Furthermore, post hoc incline effects and the difference between direct en delayed feedback may indicate the relevance of time between guess and feedback.