How groups 'cascade' to incorrect decisions

Groups of people like to share their ideas, and reach consensus before deciding what the best way to do something is. Seems like a good idea. More brains on an idea should mean more opportunity to find what is wrong with it, then odds are that the consensus should be better than the choices made by specific individuals. Right?

Maybe not. From New York Times Science section:

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.

According to the article, the idea that dietary fat causes heart disease is such an incorrect group consensus. Why?

The evidence that dietary fat correlates with heart disease “does not stand up to critical examination,” the American Heart Association concluded in 1957. But three years later the association changed position — not because of new data, Mr. Taubes writes, but because Dr. Keys and an ally were on the committee issuing the new report. It asserted that “the best scientific evidence of the time” warranted a lower-fat diet for people at high risk of heart disease.

OK. Back to the steak house, marbled beef, and I'll tell my vegan daughter to STFU. Oh, and Bluebell Ice Cream. (mmmmm! Bluebell Ice Cream!)

Wait!

Eating fat may not cause heart disease, but how many Calories are in that pound of steak?? Being fat may be a whole different thing! Right??