QUOTE : This parallel form of human automatic action is aptly demonstrated in an experiment by Harvard social psychologist Ellen Langer. 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. People simply like to have reasons for what they do. Langer demonstrated this unsurprising fact by asking a small favor of people waiting in line to use a library copying machine: Excuse me, I have five pages. May I use the Xerox machine because I’m in a rush? The effectiveness of this request-plus-reason was nearly total: Ninety-four percent of those asked let her skip ahead of them in line. Compare this success rate to the results when she made the request only: Excuse me, I have five pages. May I use the Xerox machine? Under those circumstances, only 60 percent of those asked complied.