I was jogging with Serena, our new puppy, the other day, and I became contemplative when I observed her behavior around other people. During this jog, there were at least half a dozen people that came across our path. With every one, Serena became very aggressive. The hair on the back of her neck stood straight up. She was terrified. She growled, she bared her teeth. She tried to chase after the person after they passed us (going the other way). Konan's behavior was very similar, while we had him. Kole was more friendly toward other people, but still not completely trusting as some dogs are. Of course, there may be some explanation in both nature and nurture here in this phenomenon, but I believe that nurture does play a significant role. I have heard from dog trainers and people more versed with animals than myself that dogs need to socialize in order to learn good manners. They need to be around other people and other dogs ...
Life is what you make of it.