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Friday 13 June 2014

C is for Confirmation Bias

Confirmation Bias refers to our dedicated and sometimes demented preference for information that supports our pre-existing beliefs or decisions, and our equally fervent attempts to avoid finding disconfirming evidence. We can even get to the point of taking the latter as the former (although strictly that's a different problem, the Backfire Effect).


The classic test of confirmation bias is the Wason Selection Test, where participants are invited to guess the rule by which certain numbers are chosen - e.g. 2, 4, 6 - and are allowed to ask whether any other three numbers meet the rule.  Invariably people choose examples that confirm their theory - e.g. even numbers rising by 2 - and fail to choose ones that disconfirm them - e.g. an odd number.  The rule is any three numbers in rising order.

The consequences of confirmation bias can be exceedingly serious - it was implicated in the Three Mile Island nuclear disaster and the accidental shooting down of a commercial airliner by the U.S.S. Vincennes. Unsurprisingly in the hands of a determined investor there's no amount of bad news that can shake their belief in their favorite stock. Perhaps more worryingly the same is true of surgeons, scientists and generals.


Underlying confirmation bias is the problem that we can't disbelieve something until we believe it - so holding a working hypothesis isn't a bad thing, it's necessary for us to function and it was probably advantageous when our social interactions were face to face. Waiting until we were presented with disconfirming evidence rather than seeking it out wasn't likely to confer much of a disadvantage. In our current world, full of remote social interaction and saturated in data, it's much more of an issue.


We have to train ourselves to seek disconfirming evidence and develop tactics to ensure we make ourselves consider alternatives.  Don't trust anyone who can't or won't consider that their favorite stock may not be wholly wonderful and marvelous. They may be right, even a stopped clock is right twice a day, but they sure as hell can't be trusted.

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