Tit for tat is a famous game theory strategy in repeat games. It consists of cooperating on the first move, then subsequently copying the other player’s move. It is also supposed to be a forgiving strategy; otherwise, a single defection could generate an unending cycle of mutual defections. Assuming the current conflict between the United States and Iran can be modeled as a repeat game, such as an Iterated Prisoner’s Dilemma, then the key question is: which side is most likely to forgive a previous defection or act of retaliation from the other side?
“Trembling Hand” Update (1/11): The Iranian government has confessed to accidently shooting down a commercial Ukranian jetliner.
prior probability 
I think it’s been demonstrated that the US was willing to forgive previous “defections” — but US also has unreasonable expectations about Iran forgetting past US “defections”. They are playing some kind of blended game where the short-term is tit-for-tat but the long-term takes history into account. For the US, long-term starts only about the time the last Shah went down; for Iran, long-term goes back to the early 1900’s.
Excellent points. I wonder whether the Game of Chicken is the more accurate model to apply here?