Hypnosis that attempts to retrieve the truth may actually help convince you of something false, a new study says.
The study, presented Sunday at the meeting of the American Psychological Association, shows what many doctors already believe: Hypnosis can't help you recover "lost" memories. In fact, it tends to make people more confident in false memories.
The study, by Joseph Green of Ohio State University, questioned 96 college students about the day, month and year of certain historical events. Roughly half the students answered the questions under hypnosis, while the other half performed a muscle relaxation exercise before the questions.
Once finished with the questions, the students rated how confident they were in their answers. Their answers were checked, and all the subjects were told they had at least one wrong answer. They were then given a chance to change their answers, and rank how confident they were in the revised version.
The study found there was no difference in the accuracy of the hypnotized vs. the relaxation group. Nor were there differences in the groups' confidence levels, but at the same time the hypnotized group changed fewer responses when given the chance.
"While hypnosis does not enhance the reliability of memory, there is some evidence that hypnosis leads to increased confidence in memories," said Green.
The author attributes the finding to what he called the myths surrounding hypnosis. In one of his previous studies, Green found that nearly nine out of 10 people in four countries thought hypnosis could help people recover lost memories.
"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," said Green.
That idea — no doubt launched by fictional portrayals of hypnosis — took hold in earnest in the 1970s when hundreds of police departments hired hypnotists to enhance eyewitness testimony. The results showed that hypnosis increased the amount of information recalled — but the information was not always accurate.
Again, in the early to mid-1990s there were thousands of cases clogging courts based on recovered memories. Eventually it became apparent that many of these cases were actually false memories created during hypnosis.
"There are no reliable ways to recover memory," said Michael Yapko, a clinical psychologist. "Hypnosis is not some kind of truth detector."
The Uses of Hypnosis
Although hypnosis can't recover the truth reliably, it still has many useful applications, including psychological and behavioral (such as conquering phobias), medical (such as pain control), and self-improvement, notes Carol Ginandes, a clinical instructor at Harvard Medical School.
Doctors use hypnosis in psychological applications to recover memories in the hope they can be used to treat whatever problems a patient has.
"Hypnosis enhances therapy. It facilitates access to the mind," said Claire Frederick of the Cambridge Hospital in Cambridge, Mass.
The memories recovered may or may not be true, but can be very helpful in therapy, she said.