In their book, Made to Stick, authors Chip Heath and Dan Heath write:
“Authorities are a reliable source of credibility for our ideas. When we think of authorities who can add credibility, we tend to think of two kinds of people. The first kind is the expert – the kind of person whose wall is covered with famed credentials. Oliver Sachs for neuroscience, Alan Greenspan for economics, or Stephen Hawking for physics.
Celebrities and other aspirational figures make up the second class of “authorities.” Why do we care that Michael Jordan likes McDonald’s? Certainly, he is not a certified nutritionist or a world-class gourmet. We care because we want to be like Mike, and if Mike likes McDonald’s, so do we. If Oprah likes a book, it makes us more interested in the book. We trust the recommendations of people whom we want to be like.