I've read this research before. It's really very interesting, but I have to wonder where the line is.
At what point is using this kind of method just clever, and at what point is it highly manipulative and antisocial?
That's an ethics call you have to make.
In the "no, but" approach, I see no harm in it - compliance does not result in a negative result for the other person. You're not going to do it anyway, but they're going to feel better about it than just a simple "no".
In "because I have to make copies"... your call. I wouldn't, because I'd consider this improving my result at the expense of yours.
See [1] "The Mindlessness of Ostensibly Thoughtful Action: The Role of `Placebic` Information in Interpersonal Interaction".
> Langer had people request to break in on a line of people waiting to use a busy copy machine on a college campus. The researchers had the people use three different, carefully worded requests to break in line:
> “Excuse me, I have 5 pages. May I use the xerox machine?” [60% compliance]
> “Excuse me, I have 5 pages. May I use the xerox machine, because I have to make copies?” [93% compliance]
> “Excuse me, I have 5 pages. May I use the xerox machine, because I’m in a rush?” [94% compliance]
> Using the word “because” and giving a reason resulted in significantly more compliance. This was true even when the reason was not very compelling (“because I have to make copies"). The researchers hypothesize that people go on “automatic” behavior or “mindlessness” as a form of a heuristic, or short-cut. And hearing the word “because” followed by a reason (no matter how lame the reason is), causes us to comply.
So, maybe:
"Can you just take on $LARGE_TASK?" -> "No, because $RANDOM. But I can put you in contact with X, because $RANDOM"
"Can you fix dinner?" -> "No, because $RANDOM. Maybe we can cook something together after?"
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[1] https://jamesclear.com/wp-content/uploads/2015/03/copy-machi...