▁Scient ific ▁studies ▁ ▁Christians en ▁et ▁al ▁study ▁( 2 0 0 1 a ) ▁Christians en ▁et ▁al ., ▁looked ▁at ▁behaviour al ▁differences ▁between ▁three ▁bre eds ▁of ▁dogs ▁when ▁confront ed ▁by ▁domestic ▁sheep ▁( 1 3 8 ▁dogs ; ▁El kh ounds , ▁ha re ▁hunting ▁dogs ▁and ▁English ▁set ters ). ▁Two ▁testing ▁procedures ▁were ▁used ▁and ▁shock ▁coll ars ▁were ▁used ▁to ▁d eter ▁attacks ▁on ▁sheep . ▁The ▁first , ▁a ▁path ▁test , ▁involved ▁obser ving ▁the ▁dogs ' ▁re actions ▁to ▁a ▁set ▁of ▁novel ▁stim uli ▁( rag ▁pulled ▁across ▁the ▁track , ▁bundle ▁of ▁can s ▁thrown ▁down , ▁t ether ed ▁sheep ▁at ▁ 5 m ) ▁as ▁it ▁was ▁walked . ▁The ▁second ▁test ▁involved ▁monitoring ▁the ▁dog ' s ▁reaction ▁to ▁a ▁free - ro aming ▁sheep ▁f lock ▁in ▁a ▁field . ▁In ▁this ▁study ▁they ▁identified ▁several ▁factors ▁that ▁predicted ▁a ▁high ▁hunting ▁motiv ation ▁and ▁attack ▁sever ity . ▁These ▁were ▁lack ▁of ▁previous ▁opportunity ▁to ▁ch ase ▁sheep , ▁low ▁fear ful ness ▁towards ▁gun sh ots ▁and ▁un famil iar ▁people ▁and ▁general ▁interest ▁in ▁sheep ▁when ▁encounter ing ▁them . ▁Young er ▁dogs ▁( < 3 ▁years ▁of ▁age ) ▁showed ▁more ▁pron ounced ▁initial ▁hunting ▁motiv ation ▁and ▁more ▁frequent ▁attacks . ▁El kh ounds ▁showed ▁more ▁hunting ▁behaviour , ▁more ▁attacks ▁and ▁were ▁more ▁frequently ▁given ▁electric ▁shock s ▁during ▁the ▁tests . ▁A ▁shock ▁col lar ▁was ▁used ▁to