Wow. Not long ago I was trying to test whether an idea for a certain kind of online interaction would work out the way I hoped. I built a simulation with agents that evolved their strategies, trying to optimize their own outcomes.

Maybe that's not such a good test after all.

I don't believe this outcome is optimal from an evolutionary standpoint. It requires the other player to know what your strategy is and accept the ultimatum (I will do x% better than you). The other player still has the option to reject the ultimatum, screwing over both parties.

In other words, for this strategy to work it needs "pragmatic" other players that are (a) intelligent enough to know what the other player is doing and (b) willing to accept the unequal outcome. This strategy isn't symmetric: if you turned two of these bots against each other the total outcome would be much worse than if two TFT bots played each other.

Thus it stands to reason that TFT or some small variant is still the evolutionary winner.

What I'm thinking is, it appears that players with a theory of mind may not actually use the optimal evolutionary strategy. Since humans have a theory of mind, my simulation may be a poor predictor of what my users would actually do.

I found the second link you posted when I went looking for clarification. The takeaway for me was that zero-determinant strategies do tend to win games, in that the end score of someone playing a ZD strategy is usually higher than that of someone playing a different strategy, but that both scores in such games tend to be low. Against a basic tit-for-tat player, the ZD player will win by a very small margin but the game will largely consist of mutual defections. Basic tit-for-tat, as the author points out, is never a 'winning' strategy--it always either ties or loses. Its strength isn't that it wins, but rather that it limits its losses. That characteristic of tit-for-tat is as effective against a ZD strategy as it is against any other strategy.