Prisoner's Dilemma

Biological Parallel

Vampire bats face the prisoner's dilemma nightly: share blood with a starving roost-mate (cooperate) or keep it all (defect). Sharing costs energy but builds reciprocity; hoarding maximizes short-term gain but risks abandonment when you're starving. The iterated prisoner's dilemma—repeated interactions with memory—favors cooperation via tit-for-tat strategies. Bats that defect get ostracized; consistent sharers receive help when needed. Biology proves that the prisoner's dilemma resolves when games repeat, identities are known, and cheaters can be punished.