CHICAGO -- Some people who undergo hypnosis may be influenced to develop false memories, even when warned in advance about the possibility of creating fictional past events.
In a recent study, 28 percent of subjects who underwent hypnosis were induced by a researcher to develop false memories about recent incidents in their lives. This occurred even after these subjects were warned that "hypnotized participants may confuse what they imagine with what really occurred."
About 44 percent of participants who were not warned about possible false memories -- also called pseudomemories -- were induced to develop a false memory.
The results suggest that many people have unrealistic and distorted views of the power of hypnosis, said Joseph Green, co-author of the study and an assistant professor of psychology at Ohio State University's Lima campus.
"There's a cultural expectation that hypnosis will lead to more accurate and earlier memories, but that's not true," Green
said. "Hypnosis can be helpful for some people, but it is subject to the same restrictions and pitfalls of any other memory-retrieval method."
The issue of false memories has grown in recent years as more clinicians have used hypnosis to help patients recover lost memories of early traumatic events. There has been controversy about whether these recovered memories are always real.
Green conducted the study with Steven Jay Lynn, a professor of psychology at the State University of New York at Binghamton; and Peter Malinoski, Daniel Martin, and Michael Stensland, all graduate students at Ohio University in Athens. Green presented the research Aug. 15 in Chicago at the annual meeting of the American Psychological Association.
The study included 48 undergraduate students who were shown to be highly susceptible to hypnosis. Prior to hypnosis, 32 of the subjects were read a warning that hypnosis can not make people remember things that they would not normally remember. Additional information highlighting the potential imperfections of memory were read from the guidelines published by the American Society of Clinical Hypnosis. The researchers further strengthened the warnings by including statements like "hypnosis does not improve memory" and that it "can lead to false memories." The remaining 16 participants were not read any warning.
Also, prior to being hypnotized, the subjects were asked to select a night from the previous week when they were certain they did not wake up during the night, they did not remember dreaming, and they had not used alcohol or drugs.
Participants were then hypnotized and asked to "relive" that night. During the hypnosis session, a researcher asked the subjects if they heard any loud noises at 4 a.m. like a car backfiring or a door slamming.
Following hypnosis, subjects were asked if they actually remembered hearing a loud noise at 4 a.m. on the night in question. That is when 28 percent of the warned participants and 44 percent of the non-warned subjects claimed they had indeed heard a noise that night.
"The results suggest that warnings are helpful to some extent in discouraging pseudomemories," Green said. "But these limited warnings did not prevent pseudomemories and did not reduce the confidence subjects had in those memories."
Green emphasized that the study did not attempt to test all the guidelines recommended by the American Society of Clinical Hypnosis to prevent people from developing false memories during hypnosis. However, the evidence suggests that warnings by themselves are not sufficient, he said.PEOPLE BELIEVE THEY RECALL EARLIER MEMORIES DURING HYPNOSIS
COLUMBUS, Ohio -- In a separate study, Green led a team that found people reported earlier memories from childhood when they believed they were hypnotized.
In fact, the memories recalled during hypnosis were much earlier than most researchers believe are possible.
In this study, also reported Aug. 15 at the American Psychological Association, 160 undergraduate students participated. One group of students were told "You all know how to be hypnotized even though you may not have tried to hypnotize yourself before. Close your eyes and be hypnotized." They were told that hypnosis would help them recall their very earliest memory.
Other groups were given relaxation or counting exercises and told that these would help them recall their earliest memories.
The results showed that 40 percent of those who were reportedly self-hypnotized recalled a memory on or before their first birthday. In contrast only 22 percent of those in the relaxation group and 13 percent of those in the counting group claimed such an early memory.
"Most research supports the claim that our memories typically begin around the age of 3 or 4, so it seems quite unlikely that these very early memories actually happened at the stated time," Green said.
Green said it was significant that people who reportedly hypnotized themselves were much more likely than others to claim extremely early memories.
"Many people believe that hypnosis can lead to earlier memories, although that has never been shown to be true," he said. "People's expectations about what hypnosis can do will influence what they remember."
Green conducted the study with Aaron Baumgartner, Shelly Carmean, and Rouhangiz Rasekhy, all current or former undergraduate students at Ohio State's Lima campus.