Small debts create big obligations

Cialdini calls it the rule of reciprocity: once someone gives us something, even something tiny and unrequested, we feel a disproportionate itch to give something back. He points to the Hare Krishna fundraisers who pressed a free flower into passersby's hands before asking for a donation — most people who tried to refuse the flower and hand it back were rebuffed, and having accepted the 'gift,' felt obligated to pay for it with cash.

The same logic powers free samples in supermarkets, complimentary mints with a restaurant bill (proven to lift tips), and the personalized address labels charities mail before asking you to donate. The debt doesn't have to be proportional — a $0.10 gift can extract a $20 favor, because the discomfort of feeling indebted is what drives the repayment, not the size of the original gift.

The defense isn't refusing all gifts; it's relabeling manipulative gifts as tricks rather than favors, which frees you from the obligation to reciprocate them.

Takeaway: if a gift arrives with a hidden ask attached, you owe the trick nothing.