You have to decide whether to give testimony against your confederate, (T = Temptation to defect) - or - remain silent, (S = Sucker's payoff). You are facing a ten year prison sentence; snitching out your parter in crime will cut you sentence in half AND add twice the sentence on your criminal cohort. If nobody confesses you both go free. Do you sing like a bird? Or trust your partner to keep their mouth shut?