(Embargoed for release until 9:00 AM PDT, Sunday,August 26, 2001, to coincide with the annual meeting of the American Psychological Association.)
SAN FRANCISCO - A new study suggests that hypnosis doesn't help people recall events more accurately - but it does tend to make people more confident of their inaccurate memories.
Researchers asked college students, including some who were under hypnosis, to give the dates of 20 national and international news events from the past 11 years.
Those who were hypnotized were no more accurate than others in choosing the correct dates. However, those who were hypnotized were more reluctant to change their answers when they were told they might be wrong.
The results suggest that people may have too much faith that hypnosis can help them accurately recover lost memories, said Joseph Green, co-author of the study and associate professor of psychology at Ohio State University's Lima campus.
"Clearly, myths and misconceptions about hypnosis abound," Green said. "While hypnosis does not enhance the reliability of memory, there is some evidence that hypnosis leads to increased confidence in memories."
These results support earlier survey research co-authored by Green that found nearly nine of ten people in four countries believe that hypnosis can help someone remember something that they could not remember otherwise.
Green conducted the latest study with Steven Jay Lynn of the State University of New York at Binghamton. They presented their results Aug. 26 in San Francisco at the annual meeting of the American Psychological Association.
The study involved 96 college students who were asked to give their best estimate of the day, month and year that various events occurred. These included the date the Gulf War began, the day a bomb exploded in Atlanta during the Olympics and the date that Kurt Cobain of the rock band Nirvana committed suicide.
About half the students were hypnotized before performing the task, while the other half performed a progressive muscle relaxation exercise.
In addition to giving dates, the students were asked to rate how confident they were in the estimates they gave. Afterwards, the booklets with the date estimates were collected. After 20 minutes, the students were told the booklets had been scored to determine if their dates were within three months of the actual date.
All participants were told that if they had a red star on the back of the booklet, at least one, but maybe more of the dates were inaccurate. In fact, though, the researchers had put red stars on all the booklets. The students were then given 10 minutes to review and change any of their previous estimates and give new ratings of how confident they were in their date estimates.
Results showed that the students who were hypnotized were no more accurate than those in the relaxation group. On some of the questions, none of the students were within three months of the correct date. At best, 62.5 percent were within three months of the correct date of an event.
In their ratings, the students who were hypnotized were no more confident in their date estimates than were the other students, Green said. However, participants who were hypnotized were less likely to change their estimates when told some were wrong.
Participants in the hypnosis group changed only 16.9 percent of their answers, compared to the other group, who changed 24.6 percent of their answers.
The fact that students under hypnosis said they were no more confident in their answers than did others, but were still less likely to change their answers, suggests the belief in the power of hypnosis to improve memory operates outside of conscious awareness.
"Those who were hypnotized tell you they are not confident in their answers, but their behavior - the reluctance to change their answers - suggests they must be more confident in their answers," Green said.
The reason may be the myths that surround hypnosis, he said. "It's widely believed that hypnosis somehow acts as a truth serum, that it unlocks memory and permits people to perform mental operations that they otherwise couldn't do," Green said.
These myths occur worldwide, according to research Green helped conduct. In a survey of 280 students in Australia, Germany, Iran and the United States, 88 percent said hypnosis can help people remember something they couldn't otherwise remember. There were no significant differences in this belief between countries.
Green said the results of the new study don't mean that hypnosis has no value. Any kind of technique used to retrieve memories - including the use of diaries or drugs - will produce inaccurate memories. However, the difference is that people tend to have more faith in hypnosis than they do in other memory techniques.
"While it may be true that hypnosis is no worse than other memory retrieval techniques in terms of accuracy, the downfall is that people may be more confident in memories they generate while under hypnosis," Green said. "And that's because of the belief that hypnosis is a magical truth serum."
The bottom line is that memories recovered through hypnosis, or any other technique, need to be corroborated through other means before they are accepted as true, he said.