People tend to be more receptive to what you say or request when a reason is provided. And the reason doesn't have to be super compelling—simply providing any reason can be enough.

Ellen Langer, professor of psychology at Harvard, came to this conclusion after conducting an experiment and publishing her findings in 1978.

Dr. Langer instructed her experimenters request to cut in line at a copy machine at City University of New York. The experimenters asked for compliance in three different ways:

1. "Excuse me, I have 5 pages. May I use the xerox machine?"
2. "Excuse me, I have 5 pages. May I use the xerox machine, because I have to make copies?"
3. "Excuse me, I have 5 pages. May I use the xerox machine, because I'm in a rush?"

When using the word "because", regardless of the reason provided, the experimenters were 55-56.7% more likely to gain compliance. (Notice question #2 didn't contain no new information; it was a kind of placebo.)

Now, this doesn't apply to all situations, of course. The more substantial the request, the more necessary it is to provide a compelling reason. For example, when the experimenters asked to make 20 copies instead of 5, question #3 still resulted in double the chance of gaining compliance, however, question #2 (the one that didn't contain new info) wasn't any more successful than question #1.

There's a kind of magical effect the word "because" has. As the requester, it prompts us to communicate our reasoning. As the requestee, it triggers an autopilot response, and we think, "they're giving us a reason, it must be valid". It's a shortcut our brains take.

Author Robert Cialdini cited Dr. Langer's study in his book Influence and commented:

"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."