Heuristics in experiments with infinitely large strategy spaces

We introduce a new methodology that enables detection of the onset of convergence towards Nash equilibria in simple repeated games with infinitely large strategy spaces, thereby revealing the heuristics used in decision-making. The method works by constraining on a special finite subset of strategies, called decoupled strategies. We show how the technique can be applied to understand price formation in financial market experiments by introducing a predictive measure {\Delta}D: the different between positive decoupled strategies (recommending to buy) and negative decoupled strategies (recommending to sell). Using {\Delta}D we illustrate how the method can predict (at certain special times) participants' actions with a high success rate in a series of experiments