< 0 . 0 0 1 ), ▁even ▁though ▁this ▁was ▁not ▁a ▁condition ▁under ▁which ▁shock s ▁had ▁been ▁delivered . ▁O wn ers ▁reported ▁behavior al ▁differences ▁between ▁year ▁ 1 ▁and ▁ 2 ▁in ▁ 2 4 ▁of ▁the ▁dogs . ▁ 1 8 ▁of ▁the ▁ 2 4 ▁dogs ▁had ▁shown ▁no ▁interest ▁in ▁sheep ▁during ▁that ▁period , ▁even ▁though ▁they ▁had ▁been ▁interested ▁in ▁them ▁during ▁the ▁first ▁year ▁tests . ▁However , ▁only ▁one ▁of ▁those ▁dogs ▁had ▁received ▁shock s , ▁so ▁the ▁change ▁in ▁behaviour ▁could ▁not ▁be ▁attributed ▁to ▁the ▁use ▁of ▁the ▁shock ▁col lar . ▁When ▁comparing ▁own ers ’ ▁reports ▁for ▁the ▁two ▁years , ▁the ▁dogs ▁showed ▁a ▁we aker ▁incl ination ▁for ▁ch asing ▁sheep ▁and ▁other ▁pre y ▁than ▁previously ▁( p ▁< ▁ 0 : 0 0 1 ), ▁but ▁this ▁variable ▁was ▁not ▁affected ▁by ▁shock ▁experience . ▁D ogs ▁that ▁had ▁shown ▁interest ▁in ▁sheep ▁in ▁year ▁ 1 ▁showed ▁a ▁persistent ▁interest ▁in ▁year ▁ 2 . ▁No ▁dogs ▁ch ased ▁or ▁attacked ▁sheep ▁as ▁their ▁first ▁response , ▁while ▁half ▁of ▁them ▁did ▁so ▁the ▁first ▁year . ▁During ▁the ▁entire ▁test ▁period , ▁the ▁proportion ▁of ▁dogs ▁attack ing ▁sheep ▁was ▁reduced ▁to ▁almost ▁one ▁fourth . ▁The ▁number ▁of ▁shock s ▁admin ister ed ▁per ▁dog ▁was ▁reduced ▁by ▁the ▁second ▁year , ▁and ▁only ▁one ▁of ▁the ▁dogs ▁that ▁received ▁shock s ▁the ▁first ▁year ▁needed ▁shock s ▁also