The recordings were made in two different settings: when the pooch was alone, and when he was barking at a stranger at his home's fence. (sciencemag.org)
Some can grow to bark at strangers if they are allowed to stay indoors and get accustomed to a few individuals. (wtfrenchie.com)
These are the dogs that jump at the least sound, can't hold still when company comes to visit, and won't stop barking at strangers, as examples. (pethelpful.com)