▁training , ▁dogs ▁were ▁exposed ▁to ▁prov ocation ▁by ▁a ▁dist ractor ▁dog , ▁and ▁were ▁pun ished ▁using ▁full ▁intensity ▁shock ▁if ▁they ▁failed ▁to ▁perform ▁a ▁safety ▁behavior ▁or ▁showed ▁ag gression . ▁After ▁training ▁was ▁complete , ▁and ▁the ▁dogs ▁were ▁choosing ▁to ▁perform ▁the ▁safety ▁behav iors ▁instead ▁of ▁ag gression , ▁own ers ▁were ▁taught ▁to ▁use ▁the ▁shock ▁col lar , ▁and ▁the ▁training ▁was ▁transferred ▁into ▁every day ▁situations . ▁The ▁training ▁resulted ▁in ▁a ▁long - last ing ▁and ▁complete ▁supp ression ▁of ▁ag gress ive ▁behaviour ▁in ▁the ▁dogs . ▁D ogs ▁were ▁followed ▁up ▁three ▁years ▁after ▁the ▁end ▁of ▁training , ▁and ▁the ▁reduction ▁in ▁ag gression ▁was ▁maintained . ▁ ▁Crit ic ism ▁P ET A ▁( Pe ople ▁for ▁the ▁Eth ical ▁Tre at ment ▁of ▁Anim als ) ▁oppos es ▁the ▁use ▁of ▁shock ▁coll ars , ▁stating ▁" D ogs ▁we aring ▁shock ▁coll ars ▁can ▁suffer ▁from ▁physical ▁pain ▁and ▁injury ▁( r anging ▁from ▁burn s ▁to ▁card iac ▁f ibr ill ation ) ▁and ▁psych ological ▁stress , ▁including ▁severe ▁anx iety ▁and ▁disp la ced ▁ag gression . ▁Ind ividual ▁animals ▁vary ▁in ▁their ▁temper aments ▁and ▁pain ▁th resh olds ; ▁a ▁shock ▁that ▁seems ▁m ild ▁to ▁one ▁dog ▁may ▁be ▁severe ▁to ▁another . ▁The ▁anx iety ▁and ▁confusion ▁caused ▁by ▁repeated ▁shock s ▁can ▁lead ▁to ▁changes ▁in ▁the ▁heart ▁and ▁resp iration ▁rate ▁or ▁g astro int est inal