Myth-Making: Say It Often, People Will Believe People doubt vaccine safety or evolution because they hear it so often.

Sept. 1, 2011  -- The United States is reeling from a hurricane, drought, heat waves, and even an earthquake in Virginia. And we're already well into a nasty national election campaign.

Now is the time to get those rumors flying, because science is proving what most of us already know: If you say something often enough, people will believe it, even if it seems too far out at first to be taken seriously.

Why are people so eager to embrace myths, even if there is not a shred of evidence to support them? Why are so many so eager to believe the unbelievable?

It's no surprise that myths are common in politics, but they invade every field of thought, including science, even when they have been shown to be false. They spread at lightning speed in these days of social media, 24-hour television news, and instant global communications. They aren't harmless.

And it's so easy to do.

Here's how it's done, according to a new mathematical model for rumor-mongering offered by a physicist turned linguist, Lukasz Debowski, although there's no reason to believe he intentionally planned to throw fuel on the rumor mill. His prescription, developed through incredibly complex mathematics, is this:

Say it often. Keep it short.

That formula is backed by research among psychologists and sociologists who have studied the spread of myths in recent years, including psychologist Norbert Schwarz of the University of Michigan, who found that it doesn't take many believers to spread a rumor. A single voice, heard often enough, can sound like a chorus. And it doesn't seem to make much difference whether or not that single voice is credible.

In his research, Schwarz used a flier put out by the Centers for Disease Control that was intended to knock down rumors that flu shots were harmful. Within 30 minutes after they read the flier, a fourth of the older participants in the study believed the false rumors were true, and that rose to 40 percent in just three days. Younger people fared no better. So a flier that was designed to discredit rumors actually reinforced them.

If you think that's exceptional, ask a few friends if they think flu shots can cause autism.

Gregory Poland of the Mayo Clinic in Rochester, Minn., has reason to view that with alarm. His clinic issued a news release Tuesday warning that measles are making a comeback in this country and Europe because many parents believe the inoculation has been linked to autism.

That belief grew out of a paper published in 1998 by the British medical journal, The Lancet. It has since been retracted because it was found to be based on fraudulent research. So it clearly is not true, even though some celebrities have urged parents to refuse to immunize their children against the potentially deadly virus. Thus, the myth survives clear scientific evidence.

Some scientists, including pediatricians Aaron Carroll and Rachel Vreeman of the Indiana University School of Medicine, have spent years debunking myths. It is not true that cold weather can give you a cold (colds are caused by a virus, not temperature). Frogs do not give you warts. Chewing gum does not stay in your stomach for seven years.

But the question persists: Why do so many continue to believe claims that have no basis in fact?

Many psychologists have pointed to a problem all of us have encountered. We believe some things just because we want to think they are true. Psychologist Nicholas DiFonzo adds another element. Humans have a desperate need to make sense out of a world that often seems senseless. We believe, because the alternative seems unacceptable.

And sometimes, especially in politics, it's just convenient to say you believe, even if you don't. How else can you explain so many politicians running for high office, including the presidency of the United States, who deny global climate change in the face of overwhelming evidence? Perhaps their constituents, who have heard over and over that we are partly to blame, can't buy it.

But of all the fields of science, the one that is most plagued by myths is evolution. For openers, evolution is not a theory, it is a fact. The evidence, which critics call lacking, is so powerful that virtually every major research university in the world has a department of evolutionary biology.

The debate among scientists is not over whether Charles Darwin's revolutionary ideas were fundamentally correct. They do debate details, but not the substance.

There are scores of excellent books available to anyone with a curious mind that will lay out the fundamentals of evolutionary science. One of the best is very recent, "Here Be Dragons," by Dennis McCarthy, a researcher at the Museum of Natural History at Buffalo. McCarthy's brilliant work traces the evolution of hundreds of plants and animals around the world, leading to the conclusion that the vast diversity of species could only have occurred through natural selection, or "survival of the fittest," as so apply described by Darwin so many years ago.

Evolution will remain on the front burner among myth-makers in the coming months because some candidates will chose to deny it. Chances are they will say it often, and keep it brief, and their supporters will offer them praise.

But it's ignorance, or cowardice, that will make them do it. It's not all that hard to understand one of the most important discoveries in human history.

So beware the sound bite. Especially if you hear it often.