▁personally ▁do ▁not ▁profit . ▁Some ▁research ers ▁even ▁suggest ▁that ▁al tr u istic ▁pun ishment ▁is ▁an ▁evol ved ▁mechanism ▁for ▁human ▁co operation . ▁A ▁third ▁limitation ▁is ▁that ▁pun ishment ▁and ▁reward ▁systems ▁might ▁und erm ine ▁people ' s ▁volunt ary ▁co oper ative ▁intention . ▁Some ▁people ▁get ▁a ▁" w arm ▁g low " ▁from ▁co operation ▁and ▁the ▁provision ▁of ▁select ive ▁in cent ives ▁might ▁crowd ▁out ▁their ▁co oper ative ▁intention . ▁Similarly ▁the ▁presence ▁of ▁a ▁negative ▁san ction ing ▁system ▁might ▁und erm ine ▁volunt ary ▁co operation . ▁Some ▁research ▁has ▁found ▁that ▁pun ishment ▁systems ▁decrease ▁the ▁trust ▁that ▁people ▁have ▁in ▁others . ▁Other ▁research ▁has ▁found ▁that ▁graduated ▁san ctions , ▁where ▁initial ▁pun ish ments ▁have ▁low ▁sever ity , ▁make ▁allow ances ▁for ▁unusual ▁hard ships , ▁and ▁allow ▁the ▁viol ator ▁to ▁re enter ▁the ▁trust ▁of ▁the ▁collect ive , ▁have ▁been ▁found ▁to ▁support ▁collect ive ▁resource ▁management ▁and ▁increase ▁trust ▁in ▁the ▁system ., ▁ ▁B ound ary ▁struct ural ▁solutions ▁modify ▁the ▁social ▁d ile m ma ▁structure ▁and ▁such ▁strateg ies ▁are ▁often ▁very ▁effective . ▁Ex perimental ▁studies ▁on ▁comm ons ▁d ile mm as ▁show ▁that ▁over har vest ing ▁groups ▁are ▁more ▁willing ▁to ▁appoint ▁a ▁leader ▁to ▁look ▁after ▁the ▁common ▁resource . ▁There ▁is ▁a ▁preference ▁for ▁a ▁dem ocrat ically ▁elected ▁pro tot yp ical ▁leader ▁with ▁limited ▁power ▁especially ▁when ▁people '