the prisoner's dilemma

I've decided to start an ethics program in my class after a series of ridiculously selfish and community-destroying incidents. Every Monday they get the "Ethical Question" of the week. They have till Friday to write a one page response. This week was Week 1. The goal: to get them to think about the cost/benefit of acting selfless or selfish and how trusting others impacts that cost/benefit.

I have them the Prisoner's Dilemma, a fairly well-known question used to gauge ethical development. Here's the scenario:

Two suspects are arrested by the police. The police have insufficient evidence for a conviction, and having separated them, visit each of them and offer the same deal: If you confess and your accomplice remains silent, he gets the full 10-year sentence and you go free. If you both stay silent, all we can do is give you both 6 months for a minor charge. If you both confess, you each get 5 years.

Each prisoner individually reasons like this: Either my accomplice confessed or he did not. If he did, and I remain silent, I get 10 years, while if I confess I only get 5. If he remained silent, then by confessing I go free, while by remaining silent I get 6 months.

Imagine you are one of the prisoners. What would you do? Why? What would influence your decisions?

Maybe I'll post each week's question?