Combination of continuous and binary strategies enhances network reciprocity in a spatial prisoner's dilemma game

For 2 × 2 games, especially the Spatial Prisoner's Dilemma (SPD), most previous studies have presumed that players can either cooperate (C) or defect (D); this is the so-called discrete strategy. In this paper, we define the continuous-binary strategy instead of the discrete strategy. A systematic series of numerical simulations reports that the continuous-binary strategy enhances the network reciprocity for SPD. This new strategy is based on our previous finding that continuous and mixed strategies shows more robust cooperation than discrete strategy does in boundary games of Chicken and PD (BCH) and Stag Hunt and PD (BSH), respectively. It allows us to combine the advantages of continuous and mixed strategies over the usual discrete strategy into one model.