Friday, November 13, 2009

Cascades or Consensus by Secondhandedness

In going through some of my papers I ran across an article I'd meant to blog. I think it's still relevant in explaining how a consensus by itself doesn't mean much, and how having government enforce a consensus makes it that much more difficult to correct. The article in question is by John Tierney introducing Gary Taubes' book "Good Calories, Bad Calories". Here's an excerpt of Tierney's lucid writing:
He was caught in what social scientists call a cascade.

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.

2 Comments:

Blogger John Drake said...

Psychology research shows the same effect, although the author of that research alludes me at present.

4:21 AM  
Blogger Amit Ghate said...

Yeah, there are similar findings in studies of investors as well.

6:35 AM  

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