Hypnosis, even self-hypnosis, can sometimes result in the creation of false memories - the belief that something happened even though it never did.
A psychologist at Ohio State University in Lima and fellow researchers found that even when people were warned about the possibility of acquiring pseudo-memories under hypnosis, more than a quarter of them did anyway.
Dr. Joseph Green, a professor of psychology at Ohio State and co-author of the study, said, “There’s a cultural expectation that hypnosis will lead to more accurate and earlier memories, but that’s not true.”
In the study, 48 students who had been shown to be highly susceptible to hypnosis were divided into two groups. Before they were hypnotized, 32 of the students were warned that hypnosis could lead to false memories and could not make people remember things that they would not ordinarily remember. The remaining 16 students were not given such a warning.
Then the students were asked to select an uneventful night from the previous week - a night they had uninterrupted sleep, uninfluenced by alcohol or drugs and without any dreams that were recalled. During hypnosis, the students were asked if they had heard a loud noise at 4 a.m. during that night. After hypnosis, they were asked if they recalled hearing a loud noise at 4 a.m. during the night in question. Twenty-eight percent of the forewarned students and 44 percent of those who were not warned about false memories claimed that they had heard such a noise.