Authority bias
Authority bias is giving more weight to the opinion of an authority figure than the evidence justifies, and being more easily swayed or directed by them. It can extend to topics far outside the person's real expertise.
In everyday life
In Stanley Milgram's famous experiments, many volunteers kept giving what they believed were painful electric shocks because a man in a lab coat told them to continue.
A Nobel-winning physicist says in an interview that a certain vitamin prevents colds, and you start taking it daily, reasoning that someone that brilliant must know.
Why your mind does this
We rarely have full information about a person or situation, so the brain fills gaps with what usually holds true for similar cases. Relying on categories, rules of thumb and trusted sources saves a huge amount of time and effort. For most of history, following the group and trusting experienced elders was a safe bet.
How to spot it
Ask whether this person is an expert on this exact topic, and whether they have shown any evidence.
How to counter it
Separate the claim from the person's title and look for independent evidence before acting on it.
Same family: Stereotypes
SourcesMilgram (1963)·Wikipedia