cascading mis-truths

Meant to blog about this fascinating NYTimes article earlier this week. It's basically about how some "expert" truths get thrust into common wisdom, then repeated ad nauseum. People defer assuming the first guy knows what they're talking about. Many of the examples used are from the world of medicine.

Diet and Fat: A Severe Case of Mistaken Consensus

By JOHN TIERNEY

Published: October 9, 2007

When a group of people agree on something, that doesn’t always mean they are right.

We like to think that people improve their judgment by putting their minds together, and sometimes they do. The studio audience at ''Who Wants to Be a Millionaire'' usually votes for the right answer. But suppose, instead of the audience members voting silently in unison, they voted out loud one after another. And suppose the first person gets it wrong.

If the second person isn't sure of the answer, he's liable to go along with the first person's guess. By then, even if the third person suspects another answer is right, she's more liable to go along just because she assumes the first two together know more than she does. Thus begins an ''informational cascade'' as one person after another assumes that the rest can't all be wrong.

Because of this effect, groups are surprisingly prone to reach mistaken conclusions even when most of the people started out knowing better, according to the economists Sushil Bikhchandani, David Hirshleifer and Ivo Welch. If, say, 60 percent of a group's members have been given information pointing them to the right answer (while the rest have information pointing to the wrong answer), there is still about a one-in-three chance that the group will cascade to a mistaken consensus.

A great example of just this kind of mindset and misinformation can be found in Osler's Web, book about Chronic Fatique Sydrome that I read when we lived in Fiji. It chronicles the history and personal stories of the disease, but what I most enjoyed was the political and economic process of the testing and validation. You can start with one M.D. who does a shoddy study, but happens to be well connected and influential so gets further grants, and gets to sit on panels and judge studies, determining further credibility and resources. It shows how mixed up the politics, economics and science of any health issue are.

I know how prey I am to this kind of cascading mistruth myself. I often assume others are right in their assumptions and theories. I figure they've done their homework. And if it's not my area, particularly if science or numbers are involved, I all too readily cede the authority.

Definitely check out the NYT article, and the book.