Some dogs (Max, I'm talking about you) will bark at the wind, or even nothing at all, While others (Apple) will only bark when promted to by another dog and some seldome bark (Rustee). However, dogs pick up on scents very readily, and anyone breaking into the family home would be putting off phermones (sp?) and sweat while in the process of a crime. Most if not all dogs would pick up on this scent and know something is aloof, and would bark. Mind you there are exceptions to every rule, but even the meekest of dogs will bark if they sense danger to the family. JMHO!