You can talk to your dog for hours; tell him your deepest fears and greatest aspirations. He won't understand a word. However, your expressions and movements of your body speak volumes to him.
Dogs proficiency in reading body language should come as no surprise since, as pack members, dogs have to communicate with each other without the benefit of a verbal language. Instead they communicate through conscious and subliminal signing or gesturing, and watch for the actions and reactions of the other individual.
Sure, a dog can be taught that certain words mean certain things, but because dogs do not have a language center in their brain, they can never learn syntax and will never understand sentences. If you think they're understanding what you're saying, you might be right, but not for the reasons you think.
For example, you might say, "Do you want to go outside?" As you say these words you walk toward the door, or look toward it, or gesture toward it. The dog might hear the word "door" and read your body language to construct what you are trying to communicate. Oh, so he wants to know if I want to go outside, the dog may think - completely ignoring the question and the words "do," "you," "want," "go," etc. Nevertheless, with the help of body language, the message is transmitted.
A dog's natural instinct is to look away from another dog's eyes to avoid challenging him. A stare is a challenge, and a fairly rude one at that. Dogs will naturally tend to look away from us, unless they are challenging us or we have trained them to do so. If we stare at them, unwittingly or not, the signal we transmit is one of confrontation. A dominant dog will stare back, growl, and generally escalate aggressive behavior until the other party backs down whereas a very submissive dog will squat or roll and urinate in deference.
Head and Neck Position
If a dog holds his head up high, he is confident and perhaps challenging. If he holds his head low, he is deferring, fearful or depressed. A dog will read our head and neck carriage the same way that he does another dog's. If you approach a bully dog with your head in an upright position, even if you are above his head, he may interpret this appearance as challenging – certainly not as deferment. In extreme cases, he may start to growl and act threateningly. However, if you approach the same dog with your head bowed, there is a good chance that he will recognize your body language as submissive, perhaps even as soliciting play, and may be disarmed.
Interferences Around the Head
The muzzle and nape of the neck are sensitive areas for dogs. They are sites at which the dog's mother would deliver messages of chastisement, admonishment and her leadership. When dogs grow up they seem to remember this early mode of communication and many retain sensitivity regarding interferences in these areas. In dogfights, most of the 'legal' action is directed toward the head. Muzzle- or scruff-grabbing are favorite fight moves. When humans come along and grab a dog by the muzzle or scruff they are asking for trouble. Whether they get it or not depends on their perceived level of authority.
Height From the Ground and Body Position
Being high up and/or on top of another dog is a way that signals dominance. A dominant, in-charge individual will rise up to his fullest height and may literally take the high ground when approaching and signaling his seniority to a more inferior creature. On reaching the other dog, he may rest his head or a paw on the other dog's back. Mild mannered acceptance of such challenges from above will be viewed as concession and submission.
When people tower over a dog, lie on him, or rest a hand on him, the message is similar. The response, however, depends on the relationship between the person and the dog. A dominant dog may repel such a challenge to his rank while a submissive dog may squat and urinate. The message is opposite if a person lies on the floor next to a dog, allows the dog to sit next to him on a couch, or permits the dog to sit on his lap. In these instances, the sent and received is one of social equalization or deference on your part. With respect to lap sitters, an easy way to remember the social implications of such placement is to consider the rhetorical question, "In this situation, who is the king and who is the throne?"
Fearful dogs are less afraid of people who are sitting down - because they feel less threatened. Sitting down on the floor can cause an anxious dog to approach you whereas previously he would not have dome so. If you stand up, the dog may back away. If you drop to one knee, the dog may approach once more. So powerful is the effect of your position relative to the dog that you can yo-yo him into an exact place in a room by altering your height from the ground.
While floor-sitting may not be a problem with mild-mannered dogs, more dominant dogs may take advantage of the situation and send a strong signal of their authority – particularly if the person is doing something displeasing to the dog, like petting him the wrong way or for too long. The positional effect is even more pronounced when it involves children because they start out at a hierarchical disadvantage.
Forward Body Motion
Just as you can signal to a dog by adjusting your height from the floor, so can you send messages by means of your approach. A direct, full frontal approach is a confident, semi-challenging one from dog to dog or person to dog. You should never walk directly toward a dog you don't know in case he's dominant, particularly if he happens to be eating, resting, or chewing on a bone. He may bite. Also, you should never walk directly toward a dog that is fearful of people, as your sudden approach will likely be viewed as threatening, even if your words and intentions are entirely honorable. A fearful dog should always be approached indirectly using a curved trajectory.
Many of the behaviors and postures we engage in during the course of our interactions with dogs are construed or misconstrued by them in terms of body language.