I don't know if this is the same thing or not, but, theres these guys that use to work next door at my old place, and not to be rude or anything, but I think they were like drunks or crazy or something..I don't know, but I didn't trust them anyway. I was walking Jo once, and once of the guys was walking down the sidewalk beside me and Josie started to howl at him till he walked by. She's never in her life barked at anyone when shes on her leash, so I don't know about that. Rufus some how could tell if someone was a mail/milk man..He hated them, my bro thinks the milk man hit him once but I don't remember the story..Anywho, he'd only ever bark at them when we're out for walks..I really don't see how he could tell the difference, maybe he just felt like barking..