Repeating the verbal cue “sit, sit, SIT”, will decrease the reliability of the dog by up to 25%.
Avoid repeating verbal cues, give a cue, if the dog does not perform after hearing it, wait or lure with a treat to the position.
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By repeating the cue the dog learns they don’t have to listen to the first cue, only when your voice gets slightly louder and tenser by the third time.
Do not use the command if you are not 90% sure that the dog will perform. Once the cue is given, do not let your dog ignore or skip it. Be consistent and insist they respond on the first cue.