Semmann Dirk, Krambeck Hans-Jürgen, Milinski Manfred
Department of Evolutionary Ecology, Max Planck Institute of Limnology, 24306 Plön, Germany.
Nature. 2003 Sep 25;425(6956):390-3. doi: 10.1038/nature01986.
Collective efforts are a trademark of both insect and human societies. They are achieved through relatedness in the former and unknown mechanisms in the latter. The problem of achieving cooperation among non-kin has been described as the 'tragedy of the commons', prophesying the inescapable collapse of many human enterprises. In public goods experiments, initial cooperation usually drops quickly to almost zero. It can be maintained by the opportunity to punish defectors or the need to maintain good reputation. Both schemes require that defectors are identified. Theorists propose that a simple but effective mechanism operates under full anonymity. With optional participation in the public goods game, 'loners' (players who do not join the group), defectors and cooperators will coexist through rock-paper-scissors dynamics. Here we show experimentally that volunteering generates these dynamics in public goods games and that manipulating initial conditions can produce each predicted direction. If, by manipulating displayed decisions, it is pretended that defectors have the highest frequency, loners soon become most frequent, as do cooperators after loners and defectors after cooperators. On average, cooperation is perpetuated at a substantial level.
集体努力是昆虫社会和人类社会的一个标志。在昆虫社会中，集体努力是通过亲缘关系实现的，而在人类社会中，则是通过未知机制实现的。在非亲属之间实现合作的问题被描述为“公地悲剧”，预示着许多人类事业将不可避免地走向崩溃。在公共物品实验中，最初的合作通常会迅速降至几乎为零。可以通过惩罚背叛者的机会或维护良好声誉的需要来维持合作。这两种方案都需要识别背叛者。理论家们提出，一种简单而有效的机制在完全匿名的情况下运作。通过自愿参与公共物品博弈，“独行侠”（不加入群体的参与者）、背叛者和合作者将通过石头剪刀布的动态关系共存。在这里，我们通过实验表明，自愿参与在公共物品博弈中产生了这些动态关系，并且操纵初始条件可以产生每个预测的方向。如果通过操纵显示的决策，假装背叛者的频率最高，那么独行侠很快就会变得最频繁，在独行侠之后是合作者，在合作者之后是背叛者。平均而言，合作在相当程度上得以延续。
