Fig. 2.
The transitions of MaRS among the choices of cooperation (marked as “C”) and defection (marked as “D”) for a repeated PD game. The arrows are marked with ordered triples (opponent’s last move, passive similarity rank, reactive similarity rank) defining the conditions for each type of transition. Plus sign, minus sign, and question mark indicate whether the current value of the similarity index, either psp or psr, is above (or identical) or below the similarity threshold ps*, or whether its value has not yet been determined, whereby ps* = (T − S)/(T − S + R − P). An asterisk accounts for all possible states of the similarity indices; a question mark indicates that the value of the index is yet undefined. Each triplet is labeled with the relevant type of mimicry: enacted, expected, or excluded. Note that, for all cases of enacted mimicry, the passive similarity value is above the similarity threshold (+), and that, for all cases of excluded mimicry, the passive similarity value is below the similarity threshold (−). Also note that, in the case of expected mimicry, MaRS cooperates twice. t = 0 indicates that the game is about to begin.