First model to capture crosstalk in social dilemmas

The idea that previous interactions can affect unrelated future decisions might seem obvious: the stranger in front of you pays for your coffee, and then you pay for the stranger behind you. You’ve had no interaction with the latter, and no reason to do them a favor, but you do it anyway. Similarly, if a friend refuses to help, you might be less inclined to help the next person who asks you for something. These are both instances of crosstalk — previous interactions affecting unrelated future decisions — and though this notion might seem natural, it had never before been incorporated into simulations of groups engaging in repeated social dilemmas.