Hi Rojo,
Appreciate the insight, but I'm pretty sure the payoff structure of needing to push the pace to get the standard in a 1500m Trials final is actually Stag Hunt, not Prisoner's Dilemma.
A Stag Hunt game is one in which all the players can cooperate to earn a bigger prize (the stag), which can only be won if they all cooperate. However, they are unsure if one of the players will defect to earn a smaller prize (a rabbit) and ruin the hunt for the rest of them (they go hungry). So, every player is incentivized to defect to go for the smaller prize (which, at best, leaves all but one of them hungry, and even he does not eat as much as he could). The 1500 guys without the standard need to cooperate and share the lead to push the pace, but without being certain that they will get any help from their fellow standard-chasers, they are incentivized to settle for the smaller prize (a higher place in the Trials, but no chance of Olympics). The best situation for everyone is one in which everyone cooperates, as this has the highest payoff for every individual player.
Whereas in Prisoner's Dilemma, defecting when everyone else cooperates is the most preferable situation for every player, as this has the highest payoff for the defecting player. The difference is subtle, but important for thinking about why those without the standard really, really should chase it in the final if they think they have a chance. Unlike in a prisoner's dilemma, when people push the pace, all the guys with the standard win more.
Just thought an Ivy League-educated econ major should know the difference :)