My dog has recently developed a bad habit of barking at most other people and dogs on our walks. It's a problem only because I have neighbors in my apartment building. He will occasionally bark a lot even at my immediate neighbors, who he knows well. (He's always on a leash when he does this - when he's playing off leash in the park he's not a barker.) He gets regular playtime with other dogs and people, but since it's just him and me in my apartment, he could be getting protective. He and the dog who lives upstairs just plain don't like each other, but I'm wondering about ways to get him more adjusted to all the regular sights and sounds around him.