In many cases, the prisoner’s dilemma game is played over a series of trials, in which players can modify their responses based on those given by their partners on previous trials. For example, the ongoing arms race between neighbors and rivals India and Pakistan can be seen as a social dilemma that occurs over time. Over a period of years, each country chooses whether to compete (by building nuclear weapons) or to cooperate (by not building nuclear weapons). And in each case, both countries feel that it is in their best interest to compete rather than cooperate.
The prisoner’s dilemma can also be expanded to be played by more than two players. The behavior of individuals leaving a crowed parking lot, as an example, represents a type of prisoner’s dilemma in which it is to each person’s individual benefit to try to be the first to leave. However, if each person rushes to the exit without regard for others, a traffic jam is more likely to result, which slows down the process for everyone. If all individuals take the cooperative choice—waiting until their turn—everyone wins.