▁this ▁study , ▁means ▁there ▁is ▁a ▁high ▁risk ▁that ▁dogs ▁will ▁show ▁severe ▁and ▁persistent ▁stress ▁sympt oms . ▁We ▁recommend ▁that ▁the ▁use ▁of ▁these ▁devices ▁should ▁be ▁restricted ▁with ▁proof ▁of ▁theoretical ▁and ▁practical ▁qual ification ▁required ▁and ▁then ▁the ▁use ▁of ▁these ▁devices ▁should ▁only ▁be ▁allowed ▁in ▁strictly ▁specified ▁situations ." ▁ ▁Sch ilder ▁& ▁van ▁der ▁Borg ▁study ▁( 2 0 0 4 ) ▁Sch ilder ▁and ▁van ▁der ▁Borg ▁conducted ▁a ▁study ▁to ▁compare ▁the ▁behavior ▁of ▁police ▁service ▁dogs ▁that ▁had ▁previously ▁been ▁trained ▁using ▁a ▁shock ▁col lar ▁( Group ▁S ) ▁with ▁those ▁that ▁had ▁not ▁( Group ▁C ). ▁In ▁the ▁training ▁test ▁no ▁shock s ▁were ▁applied , ▁but ▁the ▁animal ' s ▁behavior ▁was ▁observed ▁during ▁training ▁tasks . ▁The ▁intention ▁was ▁to ▁investigate ▁whether ▁shock ▁col lar ▁based ▁training ▁might ▁have ▁a ▁long - term ▁effect ▁on ▁stress - related ▁behavior ▁even ▁in ▁the ▁absence ▁of ▁shock , ▁and ▁whether ▁this ▁related ▁to ▁specific ▁features ▁of ▁the ▁training ▁context . ▁Be hav iors ▁recorded ▁included ▁recogn ised ▁indic ators ▁of ▁stress ▁( p ant ing , ▁lip - lick ing , ▁y aw ning , ▁p aw ▁lif ting ▁and ▁body ▁post ure ) ▁as ▁well ▁as ▁y el ping , ▁s que aling , ▁sn apping ▁and ▁avoid ance . ▁During ▁free ▁wal ks ▁on ▁the ▁training ▁grounds , ▁groups ▁S ▁dogs ▁showed ▁significantly ▁more ▁stress ▁related ▁behav iors ▁and ▁a ▁lower ▁body ▁post ure ▁than ▁group ▁C