What's the lesson behind the restaurant mints reciprocity study? The mint on the check is one of the most studied tricks in influence, and it teaches a precise lesson about how to give. The plain version is a coin toss. But the data shows that when the server brings mints with the bill, tips climb. Bring them, then come back and offer a second one as if the table is special, and tips climb further still. The gift didn't get bigger. The personal, unexpected, seemingly tailored quality of it did. That's the whole game. Reciprocity hits hardest when the gift feels [...]