Concept · Cognitive Bias: Persuasion and influence biases
Reciprocity bias
Origin: Cialdini, 1984
Biological Parallel
Vampire bats share blood meals with roost-mates who previously fed them—reciprocity enforced through memory and reputation. The mechanism is ancient: reciprocal altruism evolved whenever repeated interactions exceed the cost of cheating. From cleaner fish and their clients to food-sharing primates, biological reciprocity requires tracking debts and punishing defectors. Humans inherit this deep algorithmic bias: receiving triggers obligation, independent of rational cost-benefit analysis.