Sunday, 21 October 2007

Cascades of error

Several recent posts on HBL refer to this interesting John Tierny article, published in the NYT on 9-OCT-07:
Diet and Fat: a Severe Case of Mistaken Consensus

The whole article is worth reading, both for its specific discussion of the crusade against dietary fat and for showing how the mechanism of mistaken consensus leads to such crusades. An extract:
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.
The obvious analogy to the anti-fat crusade is the global warming crusade. Only heretics dare question four assumptions that have yet to be provided with a plausible foundation:

1) Long term global warming is occurring
2) Economic activity causes global warming
3) Global warming is a bad thing
4) Governments should curtail economic activity to prevent global warming

One HBLer discussed another interesting article, Science is the pursuit of the truth, not consensus, by John Kay in the Financial Times (also on 9-OCT-07). Some extracts:
Numbers are critical to democracy, but science is not a democracy. If an evangelical Christian converted all members of the Royal Society to creationism, that neither would nor should affect my belief in evolution. Most scientists know no more about climate change, HIV/Aids or the measles, mumps and rubella (MMR) vaccine than do most lawyers, philosophers or economists, and it is not obvious who is better equipped to assess conflicting claims on these issues. Science is a matter of evidence, not what a majority of scientists think.
Statements about the world derive their value from the facts and arguments that support them, not from the status and qualifications of the people who assert them. Evidence versus authority was the issue on which Galileo challenged the church. The modern world exists because Galileo won.
I have to agree with that.

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