Doctors know best: Patients often ignore medical suggestions

In briefing consumers on health risks, public health campaigns often rely on a catchy strategy: They list the myths about a behaviour or product, then follow up those misconceptions with the truth.

Check any Internet search engine and you will find ‘myths and facts’ on health topics from abortion and acne to vaccines and weight loss. But new research suggests that even the sharpest consumer can be tripped up by these warnings because of a flaw in the way we remember what we read or are told.

As time passes, the studies show, people remember the health information they were given. But they forget which part was myth and which was the truth. Experts say consumers and doctors need to be aware of this problem so they can make sure that quirks of memory do not harm anyone’s health.

“Here’s what happens,” said Ian Skurnik, a psychologist and assistant professor of marketing at the University of Toronto, who worked with colleagues from the University of Michigan to study the phenomenon.

“You notice that your grandmother has been taking useless medical treatments, and you’re worried,” he said. “You tell her, ‘You know, Granny, shark cartilage doesn’t help your arthritis.’ You tell her three times to make sure she understands, and she seems to.” He continued, “But a few days later you talk to her again and find the warnings have had precisely the opposite effect of what you intended.” This common problem arises, he said, because in laying down a memory trace, the human brain seems to encode the memory of the claim separately from its context ? who said it, when and other particulars, including the important fact that the claim is not true.

The detailed memory of the experience of learning the information begins to fade almost immediately, and the contextual clues fade faster than the core claim. “Long after you’ve forgotten the context, the claim will still seem vaguely familiar,” Skurnik said. That is when a well-documented effect that he calls “the illusion of truth” kicks in.

Many studies over the last few decades have shown that unless people have some countervailing context or information to grab hold of, they tend to regard information that seems familiar as true.

To test the power of that effect related to health claims, Skurnik and colleagues gave 64 volunteers a few dozen bits of unrelated medical information that they were unlikely to have heard before, like “Corn chips contain twice as much fat as potato chips” and “Aspirin destroys tooth enamel.”

The researchers arbitrarily labelled half the statements false and half as true. Each item was read aloud and simultaneously presented on a computer screen at least once, but half the items appeared three times within the list. Half the volunteers were college students ages 18 to 25. The others were healthy adults, ages 71 to 86. Thirty minutes after the volunteers had seen the information, the research-ers showed them another list of items that contained all the previous statements, with some new items mixed in. They were asked to identify which statements were false, which were true and which were new. The same kind of quiz was repeated three days later.

The results, published in the March 2005 issue of The Journal of Consumer Research, showed that the older adults were much more likely than the younger ones to misremember the false statements as true, an effect that was exacerbated three days later.

What is more, having seen a statement three times in the initial list helped the younger people remember it correctly, but made things worse for the older volunteers.

“Even quite elderly people remain good detectors of information that’s new, versus something they have seen before,” Skurnik said. “But in this case, that ability worked against them.” The repetition of a warning underscored its familiarity.

The implications of the findings are not limited to older people, Skurnik said. In a follow-up study not yet published, he and his colleagues presented college-age volunteers with a health information pamphlet from the Web site of the Centers for Disease Control and Prevention called ‘Is It a Flu Shot Fact or Myth?’ In boldface type, the pamphlet contained eight statements about the flu vaccine ? six labelled false, one true and one “maybe.” Each statement was followed by a sentence or two of explanation in smaller type.

“Immediately after reading the flier, participants made few mistakes in recalling whether a particular statement from the flyer was described as a fact or myth, and there was no difference in the type of mistake,” the researchers reported. “However,” they said, “after a half an hour, participants were much more likely to misremember a fact as a myth.”

“I think the message to physicians from this study and others is that even if you have lots to tell your patient in an office visit, you have to tell them several ways and over time to make sure they understand,” said Dr Joanne Schwartzberg, who oversees the health literacy programme of the American Medical Association. (NYTNS)