I pointed this out in the other thread on this (http://news.ycombinator.com/item?id=5244777), but this isn't at all Prisoner's Dilemma even before any consideration of communication because the payoff matrix is wrong.
For a game to be PD, there must be a strict ordering of payoffs. In descending order of payoff, they must be (where "I" describes the player whose payoff is being considered, and "you" is the other player; this is the same for both players):
I defect, you cooperate
I cooperate, you cooperate
I defect, you defect
I cooperate, you defect
There are two important features that come from this set of payoffs: (defect, defect) is the only Nash Equilibrium -- the only point where a unilateral strategy change by any player makes their payoff worse, and defection is a dominant strategy for each player (that is, without knowing the other players chosen strategy, each player knows they can maximize their own payoff by defection.)
The actual ordering of payoffs for this exercise is:
I cooperate, you cooperate (I get 100% on test with no risk)
I defect, you cooperate; or I defect, you defect (I get whatever score I would get from taking the test, which is never better than 100%, and could be worse)
I cooperate, you defect (I get 0% on the test)
In this case, both cooperate/cooperate and defect/defect are Nash Equilibria, and, unlike in the Prisoner's Dilemma, and there is no dominant strategy. This is a game that has much more room for cooperation than PD, because cooperation in PD always means giving up a gain that you could have realized, where in this case cooperation is the ideal self-interested behavior if the other player is cooperating.
Just a point, that some students were there to ensure no one breaks the boycott, and if someone did, these would come in too. So, enforcing the other's decisions and changing your own after see their decision is not exactly Prisoner's Dilemma.
Nice mobilization, and nice reactio from the professor too, though.
Strictly speaking, it's not "prisoner's dilemma" if the students can talk to each other and agree on a plan. In a real prisoner's dilemma, the participants have to guess at the motivations and actions of other participants -- this is part of the game's definition:
Quote: "Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of speaking to or exchanging messages with the other."
For a game to be PD, there must be a strict ordering of payoffs. In descending order of payoff, they must be (where "I" describes the player whose payoff is being considered, and "you" is the other player; this is the same for both players):
There are two important features that come from this set of payoffs: (defect, defect) is the only Nash Equilibrium -- the only point where a unilateral strategy change by any player makes their payoff worse, and defection is a dominant strategy for each player (that is, without knowing the other players chosen strategy, each player knows they can maximize their own payoff by defection.)The actual ordering of payoffs for this exercise is:
In this case, both cooperate/cooperate and defect/defect are Nash Equilibria, and, unlike in the Prisoner's Dilemma, and there is no dominant strategy. This is a game that has much more room for cooperation than PD, because cooperation in PD always means giving up a gain that you could have realized, where in this case cooperation is the ideal self-interested behavior if the other player is cooperating.