). ▁T FT ▁is ▁character ized ▁by ▁first ▁making ▁a ▁co oper ative ▁move ▁while ▁the ▁next ▁move ▁m im ics ▁the ▁decision ▁of ▁the ▁partner . ▁Thus , ▁if ▁a ▁partner ▁does ▁not ▁co oper ate , ▁you ▁copy ▁this ▁move ▁until ▁your ▁partner ▁starts ▁to ▁co oper ate . ▁Computer ▁tournament s ▁in ▁which ▁different ▁strateg ies ▁were ▁p itted ▁against ▁each ▁other ▁showed ▁T FT ▁to ▁be ▁the ▁most ▁successful ▁strategy ▁in ▁social ▁d ile mm as . ▁T FT ▁is ▁a ▁common ▁strategy ▁in ▁real - world ▁social ▁d ile mm as ▁because ▁it ▁is ▁nice ▁but ▁firm . ▁Consider , ▁for ▁instance , ▁about ▁marriage ▁contract s , ▁r ental ▁agre ements , ▁and ▁international ▁trade ▁policies ▁that ▁all ▁use ▁T FT - t act ics . ▁ ▁However , ▁T FT ▁is ▁quite ▁an ▁unf org iving ▁strategy ▁and ▁in ▁no isy ▁real - world ▁d ile mm as ▁a ▁more ▁forg iving ▁strategy ▁has ▁its ▁own ▁advantages . ▁Such ▁a ▁strategy ▁is ▁known ▁as ▁Gener ous - tit - for - tat ▁( GT FT ). ▁ ▁This ▁strategy ▁always ▁reci proc ates ▁co operation ▁with ▁co operation , ▁and ▁usually ▁rep lies ▁to ▁defe ction ▁with ▁defe ction . ▁However , ▁with ▁some ▁probability ▁GT FT ▁with ▁forg ive ▁a ▁defe ction ▁by ▁the ▁other ▁player ▁and ▁co oper ate . ▁In ▁a ▁world ▁of ▁errors ▁in ▁action ▁and ▁per ception , ▁such ▁a ▁strategy ▁can ▁be ▁a ▁Nash ▁equilibrium ▁and ▁evolution arily ▁stable .