We observe two biases simultaneously:
"How silly to treat the difference between 97% and 100% so much differently than the difference between 33% and 34%!"
"How silly to assign 97% probability to things that only happen 70% of the time!"'
You don't get introspective access to the probabilities your brain is implicitly using, so this sort of error is unsurprising. Natural selection isn't going to do anything about it until people start making serious decisions on the basis of explicit expected value calculations.
Okay, this explanation works!
Without access to the math, we estimate probability into wide bands ("always", "usually", "sometimes", "never") and evolutionarily favor the "always" band because it is a lot less likely to have us wind up starving, and how could we save the excess from a jackpot win anyway on the savannah? When we then learn math, we learn that 99%, which before math we would count as "always" in our intuitive system, isn't actually always, and now our half-educated intuitive system ...
Today's post, Zut Allais! was originally published on 20 January 2008. A summary (taken from the LW wiki):
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