Reciprocity

We feel compelled to return favors — even uninvited or unwanted ones. This deep social norm is systematically exploited by marketers and manipulators.

• Hare Krishna members gave away flowers at airports before asking for donations — the free gift triggered reciprocity.
• Free samples at supermarkets dramatically increase purchases of that product.
• A pharmaceutical company that wines and dines doctors finds they prescribe that company's drugs more — even when cheaper alternatives exist.