Imagine a wolf and a chimpanzee trying to get along.
Even if they were friendly, they would never be able to fully understand each other their instincts and body languages are just too different.
Humans and dogs face a similar situation, says dog-training expert Patricia McConnell. As much as we love our dogs, we are primates, with hard-wired primate behavior, and dogs are canines with hard-wired canine behavior.
So despite our best efforts, sometimes humans and dogs flat misunderstand what the other is doing.
In her new book, "The Other End of the Leash: Why We Do What We Do Around Dogs," McConnell examines this problem from many different sides.
"It's a very different perspective," she says. "It's a whole new way of looking at the relationship in a practical, functional way."
McConnell got the idea of comparing the four species human, chimp, dog and wolf while watching a video of chimpanzees.
"It was like the clouds parted," she says. "I saw them do something to each other that dogs hate that pat-pat-pat on the top of the head. Dogs hate that.
"I went, 'Wait a minute, that's what the people were doing last night (in a dog-training class)."'
The people were simply following a pattern that they're programmed for, she says, realizing that humans pat each other in many situations.
In trying to train a dog, she says, "it really becomes clear that what you are really doing is training the people. And what all dog trainers will agree on is it's a lot harder to train humans than it is to train dogs. And that's not because we're stupid, it's because we're us.
"We don't come to this relationship without any baggage."
Take the simple act of trying to teach a dog to lie down. A trainer can tell an owner not to repeat the command "down," only to hear the owner say, "Lie down. Come on. Down. Lie down," which only frustrates the trainer and teaches the dog that it can ignore the owner.
That's because humans and chimps are programmed to repeat sounds, getting louder if we don't think we're being heard. But dogs respect a cool, calm leader.
The similarities of human and dog behavior are what make each species love the other, she says. We're both social animals who retain youthful characteristics into adulthood such as a love of play, for instance.
But the differences, if the human doesn't understand them, can lead to a badly trained or even aggressive dog, she says.
Imagine a human walking up to a strange dog on a leash. A human, like our chimpanzee cousins, tends to go right up to someone, face to face. But that's very bad manners to a dog, which likes a side-by-side approach, as anyone who has seen two strange dogs sniff each other knows. Thrust your face in the face of an unfriendly dog, and you're asking for a bite, she warns.
And indulging a dog in its every wish, such as petting it every time it nudges you, can make the dog feel like it's in charge, increasing the chances that some day it may bite if it doesn't get its way.
Dogs, for their part, are incredibly sensitive to how humans hold their bodies, she says. Leaning forward ever so slightly is a dominant move, while leaning back signals submission, for instance. The human might not ever be aware that he or she is standing one way or the other, or what it means.
Interspersed throughout the book are practical tips about training, each accompanied by clear explanations of what the human is trying to accomplish, whether it will work with a dog, and why or why not. (She also warns that some of the techniques in the book should not be tried on an aggressive dog without professional help.)
Take getting a dog to "come": The usual human posture facing the dog or even moving forward triggers the dog's instinct to stay put.
However, bowing, then backing away from the dog while clapping hands and making it a game will bring the dog, she says, because you're mimicking its natural movements.
And what if you want to stop your dog from climbing on you when you're sitting down? Primates tend to use their hands to push someone away, but dogs use their shoulders or hips to push. So if you see your dog on the way over, lean forward to occupy the space on your lap, then use your shoulder to block it.
Just don't try it on a chimp.