
Figure 4.7 is the diagram for a seven-state finite state machine (one of
many evolved by Fogel) to play prisoners’ dilemma. The start state is
state 6, and play is begun by cooperating. In the figure, “C” denotes co-
operate and “D” denotes defect. The input alphabet comprises [(C,C),
(C,D), (D,C), (D,D)], where the first letter represents the finite state ma-
chine’s previous move and the second the opponent’s. So, for example, a
label of C,D/C on the arrow leading from state X to state Y means that if
the system is in state X and on the previous move the finite state ma-
chine cooperated and the opponent defected, then cooperate and transi-
tion to state ...