Authority bias is the human tendency to attribute more authority and knowledge to people in authority (fame, power, position, etc.) than they can actually possess.
As an example, companies often use celebrities as spokespeople , knowing that the public will recognize that person and give greater credit to what they have to say than to an unknown individual. So, think twice when you see an actor endorsing dog food and remember that he is not a scientist, a nutritionist or a dog specialist – he is a paid spokesperson.
This is also why in many health care advertisements there is someone in a lab coat promoting or encouraging treatment – people see someone in a lab coat as an authority who knows what is right.