Ben Franklin effect

Biological Parallel

Grooming investment predicts alliance strength in primates—but the causation is bidirectional. Monkeys groom allies, yes, but grooming also *creates* alliance: the act itself generates commitment through sunk investment and reciprocity obligation. Similarly, helping triggers self-justification: 'I invested in this relationship, therefore it must be valuable.' Biology reveals the mechanism: costly investment requires post-hoc rationalization to prevent cognitive dissonance. The favor changes the helper more than the helped.