Answer:
Selective distortion
Step-by-step explanation:
Selective distortion is the phenomenon where people interprete information based on their previous beliefs. This occurrence makes it difficult for such people to be influenced to make a purchase through advertisements.
This challenge to marketing also applies to selective attention and selective retention.
In this instance Bob reads a circular from the Department of Human Health and Safety recommending lower salt intake to prevent health problems. Because his grandmother still adds salt and remains healthy, Bob discards this information as being untrue.