Expectation bias
The tendency to see, hear, or measure what we expect and to doubt information that doesn't match. It is closely related to experimenter's bias, and it affects anyone who goes into a situation expecting a certain outcome.
In everyday life
A pilot who expects to be cleared for takeoff hears the tower's instruction to hold as a clearance.
A mechanic expects a car's rattle to come from the brakes, so on the test drive he hears it at every stop and replaces the pads, though the real problem is a loose heat shield.
Why your mind does this
Holding steady beliefs lets us act without rethinking everything each time. Favoring information that fits what we already know is fast, protects our sense of being right, and keeps our picture of the world stable and coherent.
Its family, in 30 seconds: Confirms beliefs
How to spot it
Ask yourself whether you actually heard, read, or measured this, or filled it in from what you expected.
How to counter it
Repeat back or double-check key information, especially when it matches exactly what you were expecting.
Same family: Confirms beliefs
SourcesJeng (2006)·Wikipedia