Here is an interesting article on experimental bias during parapsychology research. The suggestion is that subtle remarks and prompts made by the experimenters could have influenced the responses made by the subjects while they tried to “receive” psychic information.
An analysis of conversations that took place during ganzfeld parapsychology experiments has revealed researchers may have exerted an influence on their participants.
Ganzfeld experiments involve a ‘sender’ trying to project images from a video clip to a ‘receiver’ who is incubated, blindfolded, in a sound-proof room. The ‘receiver’ reports the images they believe they are receiving to a researcher who notes them down. Crucially, the next stage involves the researcher reviewing these images with the ‘receiver’, before the ‘receiver’ attempts to identify the video clip seen by the ‘sender’ from among three decoys.