If you've owned several dogs through the years, chances are you've had a dog lean on you.

Some dogs will lean into your legs while you're standing; others like to lean into you when you're sitting or lying down. But why do dogs do this? As with many things associated with dog behavior, the correct answer is: it all depends on the circumstances.

To Assert Dominance

Leaning on other dogs (and in some instances humans), can be a sign of dominance. If your dog leans against a dog he doesn't know, he may be sizing up the other dog. "Hmmm," your dog is thinking, "this guy is a lightweight; I can take him." Or he could be thinking, "Whoa! He is way too big! I'd better be nice." If a dog is leaning on another dog or a human to prove his dominance, expect him to show other signs of aggressive behavior, such as holding his tail stiff and sticking straight up; having his ears up or back; and perhaps even baring his teeth.

To Protect or Claim His Human

If you're at the dog park with your dog, and your dog comes running over and leans against you, he could be telling other dogs, "Okay, everybody: this is my human. You can't have her." If you're with other people and your dog leans on you, he may again be telling everyone that you belong to him. But he may also perceive a threat. He could be leaning against you to let everyone assembled know that you have a guard dog. It also puts him in close proximity so he can spring into action to protect you should the situation arise.

He May Be Afraid

Thunderstorms, fireworks and other loud noises, and a myriad of other things can cause some dogs to be frightened. If your dog is afraid, he may lean against you to reassure himself that you're there and that he's safe. After all, he knows you do your best to keep him out of harm's way.

To Show Affection

But another reason, and by far the most common reason, is for affection. Your dog loves you very much. He thinks the sun rises and sets on your shoulders. He can't talk, so he has to show affection in other ways. Leaning is one of those ways. It's sort of a doggy hug. He may also be asking for affection from you. Our dogs love to be petted, hugged, or otherwise shown affection by us. He may lean against you in the hopes you'll reach down and scratch his ears or give him a pat on the head. Dogs are pack animals. Instinct tells them to take comfort in feeling others around them. Many dogs will fall asleep with as much of their body touching their human as possible. One word of caution: if all of a sudden one day your dog starts leaning as he walks, take him to the vet. It could be a sign of an ear infection or other serious condition that requires medical treatment. As with all things dog, why your particular dog does what he does is because he's the dog that he is. You will always be the world's foremost authority on your own dog. Follow your instincts for interpreting what you dog wants and/or needs when he leans into you, and you won't go wrong.