We show that for many classes of symmetric two-player games, the simple decision rule 'imitate-if-better' can hardly be beaten by any strategy. We provide necessary and sufficient conditions for imitation to be unbeatable in the sense that there is no strategy that can exploit imitation as a...

In economics, the standard approach to language is that talk is cheap. Here, instead, language is a social convention that affects utility. Unless language is used in its ordinary sense, it cannot help to coordinate actions because there is no way of decoding it. This points to a unique...