
with only a small modification. DOWNING was an attempt to simulate
behaviors seen in human subjects in a prisoners’ dilemma situation. It
deliberately tried to understand the other player’s approach and make
the decision that seemed likely to yield the best long-term payoff.
DOWNING started out by defecting on its first two moves, provoking
some of the other strategies to retaliate, thus lowering its total score.
When Axelrod tried a MODIFIED DOWNING strategy that began with
cooperation, it easily beat all the other programs, including TIT-FOR-
TAT.
Axelrod also noted that the success of TIT-FOR-TAT depended on the
length of the game, and it may not do ...