We seek an evolutionary explanation for why in some situations humans maintain either optimistic or pessimistic attitudes toward uncertainty and are ignorant to relevant aspects of their environment. Players in strategic games face Knightian uncertainty about opponents’ actions and maximize individually their Choquet expected utility with respect to neo-additive capacities (Chateauneuf et al. 2007) allowing for both an optimistic or pessimistic attitude toward uncertainty as well as ignorance to strategic dependencies. An optimist (resp. pessimist) overweighs good (resp. bad) outcomes. A complete ignorant never reacts to opponents’ changes of actions. We focus on sub- and supermodular aggregative games and provide monotone comparative statics w.r.t. optimism/pessimism. With qualifications, we show that in finite populations, optimistic (resp. pessimistic) complete ignorance is evolutionary stable and yields a strategic advantage in submodular (resp. supermodular) games with aggregate externalities. Moreover, this evolutionary stable preference leads to Walrasian behavior in these classes of games.

我们寻求一种进化论的解释，来解释为什么在某些情况下人们对不确定性持乐观或悲观态度，而对环境的相关方面却一无所知。战略游戏的玩家面对骑士行为方面的不确定性，并在新可加性方面分别最大化其Choquet预期效用（Chateauneuf等，2007），这使得他们对不确定性持乐观态度或悲观态度，对战略依赖性也无知。乐观主义者（悲观主义者）胜过好事（悲观主义者）。一个完全无知的人永远不会对对手的行动做出反应。我们专注于亚模块化和超模块化的综合游戏，并提供乐观/悲观的单调比较静态数。凭资格证明，我们表明在有限的人群中，乐观（resp。完全无知是悲观的，在进化上是稳定的，并且在具有总体外部性的亚模块（或超模块）游戏中产生了战略优势。而且，这种进化的稳定偏好导致了这类游戏中的Walrasian行为。