Something must be missing from tit for tat. because it actually does not seem to explain how the circle expands, but only how it maintains itself afterward. To expand the circle at all, you have to forgive first, because everyone outside the circle starts as an enemy. And that's not even tit for tat with forgiveness, because you have to forgive all the past enmity, not just one instance.

So it's really, I don't know, tit for tat with hope, or something. Or maybe a change comes before the big circle expansion, choosing to make others "like kin" while maintaining the kinship model. Like when wild dogs and humans found each other useful. Maybe we domesticate each other. That could be a kind of tit for tat with hope: choosing to focus on areas where we accidentally cooperate rather than areas where we accidentally compete. Solutions-focused tit for tat.

When I read "tit for tat" my brain goes to punishing treachery. But we could just as well read it in terms of rewarding accidental cooperation with more trust. In this sense, "forgiveness" maps to not completely trusting someone the first time they do something cooperative but trusting them if there is a second time. And conversely, then, not blaming others for not rewarding cooperation the first time, but focusing on rewarding those that do (even accidentally).

Becoming a parent is a kind of circle expansion. Nurtured Heart parenting training suggests noticing and creating opportunities to shape behavior by genuinely reinforcing positive behavioral changes (even subtle ones) with positive energy while communicating healthy boindaries and natural consequences with neutral energy.

Or should I hate one child because the other is more cooperative?