▁the ▁second ▁year . ▁The ▁observations ▁that ▁both ▁rece ivers ▁and ▁non - rece ivers ▁of ▁shock s ▁the ▁first ▁year ▁showed ▁a ▁reduction ▁in ▁the ▁probability ▁of ▁ch asing ▁sheep , ▁but ▁the ▁rece ivers ▁showing ▁a ▁larger ▁reduction , ▁show ▁that ▁shock ▁treatment ▁provides ▁an ▁additional ▁learning ▁response . ▁No ▁ad verse ▁effects ▁on ▁the ▁dogs ▁were ▁observed ▁with ▁this ▁training ▁procedure , ▁but ▁in ▁their ▁discussion ▁the ▁authors ▁commented ▁" In ▁order ▁to ▁ensure ▁no ▁negative ▁effects , ▁we ▁recommend ▁that ▁the ▁electronic ▁dog ▁col lar ▁may ▁be ▁used ▁for ▁such ▁purposes ▁only ▁if ▁it ▁is ▁used ▁by ▁sk illed ▁train ers ▁with ▁special ▁compet ence ▁on ▁dog ▁behaviour , ▁learning ▁mechan isms , ▁and ▁of ▁this ▁particular ▁device ." ▁ ▁Sal g ir li ▁dis sert ation ▁( 2 0 0 8 ) ▁The ▁aim ▁of ▁Sal g ir li ' s ▁study ▁was ▁"... to ▁investigate ▁whether ▁any ▁stress ▁is ▁caused ▁by ▁the ▁use ▁of ▁specific ▁condition ed ▁signal , ▁qu itting ▁signal , ▁and / or ▁pin ch ▁coll ars ▁as ▁alternatives ▁to ▁electric ▁training ▁coll ars , ▁and ▁if ▁they ▁do ▁so , ▁whether ▁the ▁stress ▁produced ▁in ▁the ▁process ▁is ▁compar able ▁to ▁the ▁one ▁with ▁electric ▁training ▁coll ars ." . ▁The ▁study ▁population ▁were ▁a ▁group ▁of ▁ 4 2 ▁adult ▁police ▁dogs . ▁The ▁qu itting ▁signal ▁was ▁a ▁condition ed ▁fr ustration ▁equivalent ▁to ▁negative ▁pun ishment . ▁It ▁was ▁condition ed ▁by ▁associ ating ▁failure ▁to ▁obtain ▁an ▁anticip ated