Remember tit for tat? I will cooperate if you do, but otherwise I defect. Many consider this to beeconsidered the best way to play in repeated prisoner dilemma situations. But the old wisdom is being revised:
…the Southampton team submitted 60 programs. These, Jennings explained, were all slight variations on a theme and were designed to execute a known series of five to 10 moves by which they could recognize each other. Once two Southampton players recognized each other, they were designed to immediately assume “master and slave” roles — one would sacrifice itself so the other could win repeatedly.
If the program recognized that another player was not a Southampton entry, it would immediately defect to act as a spoiler for the non-Southampton player. The result is that Southampton had the top three performers — but also a load of utter failures at the bottom of the table who sacrificed themselves for the good of the team…
Our initial results tell us that ours is an evolutionarily stable strategy — if we start off with a reasonable number of our colluders in the system, in the end everyone will be a colluder like ours,” he said.
This, by the way, is how the Soviets used to win chess tournaments. Throw games to the leading Soviet player, and fight especially hard against the leading non-Soviet rivals.
I have not seen the primary information on the games or the program, but I suspect that some caveats are in order. First, simulated game results usually are sensitive to the choice of parameter values. Second, this strategy may be appropriate for genetically-related teams, but otherwise it will not be implemented in the real world without side payments or coercion (both are typically prohibited in the game in question).