Prisoner's dilemma

http://en.wikipedia.org/wiki/Prisoner%27s_dilemma

The cops have caught two prisoners and do not have sufficient evidence. They decide to put them in seperate cells and give the choice to either betray the other person and be free or be silent.

Case  Prisoner 1           Prisoner 2
1)    Betray (go Free)     Silent (10 year Jail)
2)    Silent(10 year Jail) Betray (go Free)
3)    Silent(6 month Jail)  Silent (6 month Jail)
4)    Betray(5 year Jail)  Betray (5 year Jail)



What would you do? 

Game theory deals with this topic nicely.