You've heard the old sayings, don't show fear, be the boss, etc. While impressive, it is not some sort of a sixth sense that they possess. They are masters at reading intent through body language. A skill that we've developed as well, but they rely on it more than we do because they have no language to state intent. Think about it, how many times have these questions been helpful tools for us? can i help you?, do i know you?, is there a problem here? etc. Dogs lack this ability. When a stranger approaches, the dog has little time to decide for itself how it feels about this infiltration of space. Nervous dogs shy away while healthier dogs are more accepting. The thing to keep in mind though, is that one way or the other our presence doesn't go unnoticed. Trainers who are experts are reading dog body language and intent can also display it. They use their bodies like magnets to draw the dog near, or to push it away. Through manipulation of body language they can project themselves as very inviting, a dog is more likely to gravitate toward them. A different approach could send the dog a more territorial message. One that clearly tells the dog, "this is my space, you are to leave it at once" the unwelcome dog will most likely retreat. Really good handlers can set and maintain a bubble of space for themselves that a group of dogs will respect. Like magnets placed end to end the wrong way round, if the handler moves in their direction they'll fall back and maintain their set distance.
Keeping this in mind, we have the ability to use this to our benefit when training dogs. When teachinga dog to "come" and "sit" or a "place" command off leash, we can use our bodies to draw the dog toward the desired location. Instead of pointing and telling an untrained dog to go to his/her kennelwhile they stare at you in confusion, we can head toward the kennel ourselves and display fun, inviting body language to draw the dog near. Once the dog is right alongside the kennel, it's much easier to get it inside and teach the command.
When working with stubborn or aggressive dogs, it's most important to be able to control space. A territorial dog will lunge at strangers entering it's home unless it's owner controls space in the home. The owner must be able to push the dog away from the door and be able to command it to a down stay to break the habit of reacting to strangers. This won't happen though, unless the dog understands to respect the owners required ammount of space which isn't a set ammount. If i want you here i'll draw you in, if not i'll push you as far away as i see fit.