This is one of the reasons why talk is not a substitute for moves. Moves can in some way alter the game, by incurring manifest costs, risks, or a reduced range of subsequent choice; they have an information content, or evidence content, of a different character from that of speech. Talk can be cheap when moves are not (except for the “talk” that takes the form of enforcible threats, promises, commitments, and so forth, and that is to be analyzed under the heading of moves rather than communication anyway). Mutual accommodation ultimately requires, if the outcome is to be efficient, that the division of gains be in accordance with “comparative advantage”; that is, the things a player concedes should be those that he wants less than the other player, relative to the things he trades for. Each needs, therefore, to communicate his value system with some truth, although each can also gain by deceiving. While one’s maneuvers are not unambiguous in their revelation of one’s value systems and may even be deliberately deceptive, they nevertheless have an evidential quality that mere speech has not.

XREF: Connects to the classic economics principle that costly signals and revealed preferences carry more information than cheap talk.

Thomas C. Schelling, The Strategy of Conflict, loc. 282