How did cooperation evolve ?

I have learned a lot from Scientific American. In January, 1983, Hofstadter presented these questions:

1. "Can cooperation emerge in a world of pure egoists ? How can cooperation get started at all ?"

2. "Can cooperative strategies survive better than their noncooperative rivals?"

3. "Which cooperative strategies will do best , and how will they come to dominate ?"

He reported on a computer tournament that Axelrod, from the University of Michigan, organized and that showed how it could be done.

There were 3 contests. For the first 2 contests people were invited to present computer programs that would meet all the other programs 200 times. These programs would respond to the others with a "C" (cooperation) or "D" (defection) The points were noted as such:

a, If both programs gave a C then they would both get 3 points.

b. If they both defected, they would both get 1 point.

c. In the case where one was C and the other was D, C would get 0 points and D would get 5.

The program that amassed the most points was the winner.

This is similar to what is called the Prisoner's Dilemma.

In the first tournament 15 programs were entered. The programs had from 2 to 77 lines. They were met with the other programs and a clone of itself. This tournament was run 5 times to make sure about statistical fluctiations. In this tournament the winner was the shortest program, called Tit for Tat. The lines were :

1. When meeting another program always start with a C.

2. When meeting again with another program copy what the other program sent the last time that it met this program.

Axelrod called the programs that didn't defect before its opponenet as "nice", and he called the programs that did not hold a grudge as "forgiving". In a replay of this tournament he added 2 other programs that had these qualities and came out as the winners.

After publishing the results Axelrod invited more people to join in for another round. This time there were 63 programs ranging in length from 2 lines to 152 lines. Tit for Tat won again. The other 2 programs that Axelrod had added and that won previously did not win this time, showing that Tit for Tat was more "robust".

He said "One striking fact about the second tournament is the success of the "nice" rules of the top 15 finishers . Only one was not nice. The bottom 15 finishers had only one that was nice."

From the second tournament another strategy, called "provocability" emerged - the idea that one should "get angry" quickly at defectors and retaliate. Thus a more general lesson is "Be nice, provocable and forgiving."

The third tournament was an ecological replay of the second. The top programs were ranked according to their place and rewarded with copies of themselves in the next generation tournament. A number of the bottom programs were eliminated. Through generation after generation more of the poorer programs dropped out and the good ones flourished. The one not nice program that was initally at the top started to weaken after 200 replays and became completely extinct by the 1000th replay. .

Tit for Tat won the tournaments not by beating any other player, but by eliciting behaviour that allowed both to do well. It was so consistent at eliciting mutually rewarding outcomes that it attained a higher overall score.

There are samples from everyday life - a business partner that never cheats anyone doesn't try to lessen the profits of others, but rather just tries to do well for himself. Hofstadter continues in his article to point out where relationships between businesses and even between countries could benefit from the ideas that were learned in these tournaments.