In social tasks, communication and task execution are often co-dependent, yet they represent a tradeoff. We present a cognitive model of an experimental task consisting of a collaborative and competitive game played by groups of human participants organized in a small-world graph. In an experiment involving teams of humans playing a cooperative game, the effect of local communication policies on the efficiency and the performance of networked participants was observed. The model follows the ACT-R theory and provides a formalization of the decision-making processes and tradeoffs involved. A simulation of the hypothetical case of unnatural memory decay shows decreased performance and supports a prediction of the thesis that memory limitations have co-evolved with social structure.