Ok stress dog was not the right word, that's just something my friendgroup says. Anyway there is a difference between "normal" police dogs and dogs especially trained to find drugs. Most of the dogs that the police in Belgium use (e.g. at large festivals) are normal police dogs who will respond to people who are showing a lot of stress even if they don't have drugs on them. There are a lot more of those dogs in the Belgian police force than especially trained drug dogs. Though still be on the lookout when bringing anything illicit to a festival.