I took a parapsychology course many years ago (for a psychology university elective). One of the studies we did was a case from about 100 years ago or maybe late 1800s. The occult was fast becoming an interest around that time. For this study, a group of researchers got together and were going to have a seance to reach someone from beyond. The catch, they were very careful to make up a person, not try to reach anyone who had really existed. So they spent a good deal of time developing a life story and choosing a name for their "ghost" and making sure it would be fictitious. Then they set about making that person 'real' for them. Essentially, they started convincing themselves that person was real. They knew they were playacting, but were trying as much as possible to get into the mindset of contacting a 'real' ghost. I think they had several regular seances, complete with rituals to put them into the mindset. After awhile, of swaying and calling on their ghost and believing, things started to happen. There was a response. Their "ghost" contacted them. But that person had never existed, so what happened? The researchers determined that maybe they had somehow, with their minds and need to believe created the things that happened. They knew it wasn't the ghost, but could it have been some type of ESP? Like telekinesis? Could it have been a group hallucination? I don't think they came up with an answer, but the study was written up.