This is reminiscent of the prisoner's dilemma. If players can coordinate, c,c is the optimal outcome.But as both have the incentive to deviate, d,d is the Nash equilibrium. In other words, both say c but secretly think d. However, if they can send some message that has some meaning c,c can become a stable equilibrium.
This is different from a repeated game. There, if the same players keep interacting, they can build a reputation and c,c becomes, as experimental evidence shows, easily the equilibrium. The Demichelis and Weibull paper shows that small costs of lying can destabilize the d,d equilibrium as well. This may seem trivial, as adding such costs is equivalent to reducing the outcomes of strategy d. In the present context, however, the point is that pre-game messages ("cheap talk") are part
of the information set of actions. These messages may be complex, such as detailing what action one player takes in response to the other. But this cheap talk, even if cheap, may be effective in getting the better, cooperative outcome.