Substantial evidence has accumulated in recent empirical works on the limited ability of the Nash equilibrium to rationalize observed behavior in many classes of games played by experimental subjects. This realization has led to several attempts aimed at finding tractable equilibrium concepts...

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...