Zealots lower coordination barriers but undermine cooperation in multiplayer games

How can a small group of committed cooperators shape collective outcomes in social dilemmas? Previous studies have shown that zealots-individuals who always cooperate-can promote cooperation in prisoner's dilemmas. Yet real-world cooperation also involves multiplayer coordination problems, where their role remains less understood. Here, we examine the role of zealots in N-person stag-hunt games in both finite and infinite, well-mixed populations. We show that a minority of zealots facilitates the emergence of cooperation by lowering the barrier to coordination, but at the cost of reducing the equilibrium level of cooperation. More strikingly, zealots can create two new attractors in infinite populations-full cooperation and stable coexistence-that extend beyond the classical equilibrium of full defection or bistability between defection and cooperation (or coexistence). In finite populations, this dual effect largely persists as population size approaches infinity; otherwise, zealots either matter little or consistently enhance cooperation. Together, these findings revise the conventional view that zealots enhance cooperation in well-mixed populations, revealing instead their dual role in multiplayer coordination dilemmas. This nuanced influence may also shape broader collective problems, from collective-risk dilemmas to the emergence of social conventions.