Tit-for-tat is one of the simplest and most successful game-theoretic strategies. Initially, you behave friendly and cooperate, and then you mirror your counterparty’s previous action: If cooperative, then you continue to cooperate; if not, then not.
In an academic context, this strategy was discussed originally for the iterated prisoner’s dilemma. However, it is also relevant to many aspects of conflict research, social sciences, and everyday life: from friends exchanging messages (and writing back or not writing back) to nations fighting battles (and fighting back or not fighting back).
The strategy is simple and effective. Yet, suppose both sides adopt this strategy, and one side fails to cooperate, both may fall into a vicious cycle where they won’t get back to cooperation, and each side retaliates for the other side’s previous retaliation.
In this case, being lenient and playing tit-for-two-tats helps to avoid these vicious cycles of non-cooperation. On the flip side, this strategy can easily be exploited by aggressive strategies that rarely cooperate – and in this case, tit-fo-tat prevails, and it’s better to punish lack of cooperation immediately.
Most human interactions in everyday life are some sort of tit-for-tat game – with varying degrees of how strongly people respond and how quickly they retaliate to non-cooperative behavior. Yet, mishaps, miscommunication, and other forms of non-cooperative behavior occur almost unavoidably, and if it is only because of the noise of everyday life – someone having a bad day or simply being negligent. In this case, play tit-for-two-tats and be lenient with your fellow human beings. However, once you feel that your lenience is being exploited, retaliate immediately.
And to finish on a positive note: tit-for-tat not only works for retaliation but also for inducing further cooperative behavior! If you’re sad that no one is writing to you, message some other people first, and they will get back to you. If you’re not getting any appreciation for your work, make others feel valued first. If you want something, first give something yourself. You might get more back than expected: Research has shown e.g. that friends enjoy being reached out to more than we think.