<i>Your stomach is tempting you to defect. Your heart is telling you not to.</i><p>And then, thankfully, your brain chimes in, and reminds you that while short-term PD-like scenarios seem to reward defection, in <i>iterative</i> scenarios -- more comparable to PD-like situations we encounter in real life -- it is cooperation (or at least, not fucking your neighbor over for the sake of short-term gain) that is very strongly incentivized.