In a study with waiters, mirroring resulted in 70% higher tips compared to positive reinforcement
Psychologist Richard Wiseman created a study using waiters to identify what was the more effective method of creating a connection with strangers: mirroring or positive reinforcement.
One group of waiters, using positive reinforcement, lavished praise and encouragement on patrons using words such as “great,” “no problem,” and “sure” in response to each order. The other group of waiters mirrored their customers simply by repeating their orders back to them.
The results were stunning: the average tip of the waiters who mirrored was 70 percent more than of those who used positive reinforcement.
— Never split the difference (Page 36)