SIMULATING INTERNATIONAL-COOPERATION UNDER UNCERTAINTY - THE EFFECTS OF SYMMETRICAL AND ASYMMETRIC NOISE

The repeated prisioner's dilemma is representative of a broad range of situations in international security and trade. This article examines the effects of asymmetric noise on the emergence and maintenance of c ooperation under such conditions, The results show that positive and n egative asymmetric noise have very different effects on strategy perfo rmance. For forgiving strategies, positive noise provides a stimulus o ut of perpetual defection or unsynchronized retaliations, but also ope ns them to exploitation. For provocable strategies, negative noise tri ggers unsynchronized retaliations or perpetual defection, although thi s may be tempered by generosity and contrition. The effects of neutral noise reflects the signature of each asymmetric noise type. Of the st rategies examined, contrite tit-for-tat (CTFT) is generally one of the best performers in both homogeneous and heterogeneous systems. Moreov er, one generally sees the evolutionary models moving from heterogeneo us bilateral interaction to cooperative norms of behavior, often inclu ding or even dominated by CTFT.