The study of how people behave in the marketplace is based on rationality.  We choose to own things that tend to add value to our lives while avoiding those that do not.  Or we buy things that bring us pleasure while avoiding things that bring us pain.  We choose happy over sad.  We choose comfort over unease.  Or utility over disutility.  Other things being equal, we choose cheaper over costlier.  We choose sexy over bland.  Those are all rational choices that make us better off—real or imagined—with a given product or service than without it.  And we do a pretty good job when left alone.  But sellers try to make us believe that we want some things that we really don’t need through advertising that is misleading.  They put products and services in the hands of very attractive models, or successful sports figures.  A lot of demand is created this way by repetition—on TV, in newspapers, flyers, videos, etc.  It works.  Glamour sells.  We still do a pretty good job because there are hundreds of products and services that don’t sell regardless of how hard the Madison Avenue boys and girls try. 

Interpersonal choices are different from economic choices.  A smile on a handsome face covers up a lot of evil.  A good ol’ boy with a down home drawl can defeat an honest, competent person most of the time.  We like those who are like us.  We want to believe they can win in an international conflict even when they have never been outside of Swampville, Georgia; or we believe they can compete in a game of derivative swaps when they haven’t a clue about what a derivative is. 

So who are the persuasible types?  They are not very confident in themselves.  They have a low sense of humor.  They are future-oriented.  They rely on authorities for their insights.  They have low self-esteem.  They are conformists.  They are not achievers.  They like things to be crystal clear and have a low tolerance for ambiguous situations.   That is just a summary that is supported by at least 1,000 scientific studies.