once a person’s self-image is altered, all sorts of subtle advantages become available to someone who wants to exploit that new image. - Robert B. Cialdini

They behave in accordance with what the contrast principle would suggest: Sell the suit first, because when it comes time to look at sweaters, even expensive ones, their prices will not seem as high in comparison.

A well-known principle of human behavior says that when we ask someone to do us a favor we will be more successful if we provide a reason.

In general, when we are unsure of ourselves, when the situation is unclear or ambiguous, when uncertainty reigns, we are most likely to look to and accept the actions of others as correct.