Reciprocity

Give something first — value, help, a concession — and people feel pulled to give back.

Why it works

Humans carry a deep, cross-cultural obligation to repay what they receive; an unreturned favor creates felt indebtedness that people act to discharge. The pull works even when the initial gift was unrequested or small, and even when the return is disproportionately large.

How to do it

1. Lead with genuine, relevant value before you ask for anything.
2. Make the gift personal and unexpected — generic perks barely register.
3. When you must say no, offer a concession first; a step-down often earns a yes (reciprocal concession).

Evidence

Reciprocity is one of the more reliable findings in social psychology, demonstrated in field experiments — for example, Strohmetz et al. found that giving restaurant diners candy with the check increased tipping. Gouldner argued the norm of reciprocity is near-universal across human societies, which is why the pull shows up across so many settings. (observational)

These are individual field studies with modest samples rather than large replicated programs, so treat the specific magnitudes as illustrative. Effect size also depends on whether the gift feels sincere; transparently transactional "gifts" can trigger reactance instead.

Sources

• Gouldner, A. W. (1960). The Norm of Reciprocity: A Preliminary Statement. American Sociological Review, 25(2), 161-178.
• Strohmetz, D. B., Rind, B., Fisher, R., & Lynn, M. (2002). Sweetening the Till: The Use of Candy to Increase Restaurant Tipping. Journal of Applied Social Psychology, 32(2), 300-309.
• Cialdini, R. B. (1984). Influence: The Psychology of Persuasion. Harper Business.

Common mistake

Giving with a visible string attached, which reads as a transaction and kills the obligation it was meant to create.