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. At first glance, it appears that the crucial difference between the two requests was the additional information provided by the words, “because I’m in a rush.”

But a third type of request tried by Langer showed that this was not the case. It seems that it was not the whole series of words, but the first one, “because,” that made the difference. Instead of including a real reason for compliance, Langer’s third type of request used the word “because” and then, adding nothing new, merely restated the obvious: Excuse me, I have five pages. May I use the Xerox machine because I have to make some copies? The result was that once again nearly all (93 percent) agreed, even though no real reason, no new information, was added to justify their compliance.