Ambiguity bias
Also known as Ambiguity effect
The tendency to avoid options where the odds of a good outcome are unknown and to pick options with known odds instead, even when the unknown option might be better.
In everyday life
Given a jar with exactly half red balls and a jar with an unknown mix, most people choose to draw from the known jar, though the other could be just as good.
At a carnival you choose the game whose sign says '1 in 4 wins' over the one with no posted odds, though you have no reason to think the second is any worse.
Why your mind does this
Simple, clear options are faster to understand and easier to act on, and when time is short that speed matters. Known odds and complete information feel safer because they let us predict what will happen. Preferring the clear option often saves effort that would be wasted on puzzles we can't solve.
Its family, in 30 seconds: Simple & complete
How to spot it
Notice when missing information is the only reason you're rejecting an option.
How to counter it
Estimate a rough range for the unknown odds and compare that range with the known option.
Same family: Simple & complete
SourcesEllsberg (1961)·Wikipedia