Reciprocity
The obligated structure of exchange underlying gift economies — Marcel Mauss's three-part obligation to give, receive, and reciprocate. Marshall Sahlins mapped a spectrum running from generalized reciprocity (close kin, unspecified or unstated return) through balanced reciprocity (ongoing relationships, a roughly equivalent return expected within a defined period) to negative reciprocity (strangers, each side trying to gain advantage), with social distance as the key variable determining where a given exchange falls.