Iterated prisoner’s dilemma.

The optimal strategy is signaling alliance (to receptive partners); after that, it’s reciprocating behavior.

Teenagers (and many adults) aren’t willing to ally, so we’re left with reciprocating. Until they accept being allies is a good idea.

Game theory does not tell us that tit for tat is generally optimal. It tells us that it is optimal for a specific game with specific rules and payouts.

It is a mistake to try to translate that to using a tit for tat strategy in general, where the rules and payouts are usually quite different.

It's not even always the optimal strategy playing prisoner's dilemma. If all your opponents are playing "always defect", playing Tit-for-tat will consistently lose (because of the initial good-faith attempt at cooperation).

Right - if I recall, the story is that there were computer-simulated tournaments in which different strategies for playing the iterated prisoner's dilemma were pitted against each other, and tit-for-tat is the strategy that emerged to be the winner. So it's an empirical result showing that it is generally the most successful strategy, not mathematically shown to be optimal against every strategy.

It's not about the specific game nor the specific payout. When raising children, it's more important to teach/demonstrate that negative behaviour does have negative consequences.

I was responding to a claim about what game theory tells us.