For the Love of a Dog (19 page)

As we’ve already seen, the brain is a complicated, integrated piece of work, and all parts of it seem to play some role in our experience of emotion. However, there’s little question that the part of the brain called the midbrain is the command center of emotion in both you and
your dog. Nestled between the cerebellum and the wrinkled lobes of the cerebral hemispheres and cortex, this area of the brain has a profound effect on how you and your dog experience the world. The structures within the midbrain make up what’s called the limbic system, which drives most of your emotions. Your eyes and ears send information to your brain about what’s happening, but the small structure called the amygdala assigns emotional significance to that information. Did you just see an aggressive dog running toward your own? “Oh, no!” signals your amygdala as soon as it receives the information, and relays the emotions of fear and arousal to another structure in the limbic system, the hippocampus. This area integrates the information with stored memories of other events (perhaps a dog who looked much the same attacked your dog last year), and then passes the filtered and emotion-laden information to your decision-making brain, the cortex. In a fraction of a second, electricity sizzles and chemicals rush between millions of your brain cells, concluding with signals to your muscles to take action.

All this happens in the blink of an eye, but it still takes some time for the information to be moved from your body’s sensory systems, through several different areas of your brain and back to the muscles of your body with instructions for action. But what if you have very little time, as little as half a second? That’s when another important actor in the limbic system kicks in: the hypothalamus. It’s called “the brain of the brain” because it regulates so many of your body’s functions without involving your energy-hungry cortex. Once it receives information, the hypothalamus can directly signal your adrenal gland for “fight or flight,” while skipping the circuitry that runs up to the rest of your brain. Years ago I was bitten by a dog who lunged directly at my chest. One moment I was walking past him, and the next I was watching him bite back and forth along my forearm, which had appeared as if by magic in front of my chest. What’s relevant here is that I couldn’t have had time to make a conscious decision to move my forearm to protect my body. It just happened, thanks to the quick work of my hypothalamus, my adrenal glands, and my cerebellum.

All the structures in the limbic system play a central role in the experience of emotion in both you and your dog. The limbic system is where neurotransmitters are most concentrated, acting in conjunction
with structures like the amygdala to control your emotional life. Your dog has exactly the same set of structures, permeated with the same set of neurotransmitters. This part of the brain is commonly called the mammalian brain, because it is first seen in mammals and is absent in reptiles. It may not have been around for as many millions of years as the brainstem and the cerebellum, but it’s been around for quite a while, and is considered a relatively primitive set of structures.
¹⁴
It is
not
the part of the brain that is unique to humans; we share it with other mammals, including the one who may be lying at your feet as you read this book.

This is yet another reason why biology suggests that dogs
do
experience emotions. Surely they don’t experience them exactly as we do— the cognitive component of emotion, which we’ll talk about later, makes our experience of emotion somewhat different from our dogs’— but to argue that they don’t share the basics of fear, anger, and joy is to argue against biology as we understand it.

So far we’ve been talking about the similarities between human and canine brains, but some parts of our brains are profoundly different, and they deserve our attention as well. The biggest difference between your brain and that of your dog is in the last major section of the mammalian brain: the big gray cerebral hemispheres. These hemispheres, in humans as wrinkled as a wizened old woman, are covered by a thin layer of cells called the cortex.
¹⁵
This is where we do most of our thinking and planning, and it’s also the feature that makes our brains so disproportionately large. It’s the cortex that ultimately receives information from the sensory system, and that informs the brain what it’s seeing, hearing, smelling, and feeling. It’s in the cortex that each of us constructs our perception of the world around us, and because each of us has a different cortex, each of us lives in a slightly different world.

That’s partly because the brain of every mammal, including humans and dogs, is designed to perceive and react to only some of the information
available to it. Just as reality shows on television are highly edited, so that they present only a portion of what really happened, our brains are always editing out information and keeping only a portion of it for processing. What your brain tells you about the world around you is not a complete picture. It has been edited to keep you from being so overloaded with information that you have a mental meltdown. Even 100 billion brain cells aren’t enough to process every single piece of information available to you. Partly on the basis of genetics, partly on the basis of experience, your brain edits out things judged to be unimportant—perhaps the sound of the fan you’ve had in your home for three years, or the sight of the marks where your dog chewed on the table leg when he was a pup. Better to expend your limited brainpower to listen for the sound of your dog pacing because he has diarrhea, or to notice that his water bowl is empty.

Because of the editing function of the brain, every person, and every dog, sees the world a little differently. This is why law enforcement officials struggle to get accurate descriptions at crime scenes. It’s not just that people aren’t particularly observant of the kind of details that become important in crimes, it’s that we actually record different things. Our brains are making continuous split-second decisions about what to attend to and what to ignore, and each brain makes a slightly different set of decisions. Some of those decisions are driven by emotional memories stored deep in the limbic system, and can vary greatly depending on what has happened to an individual during his or her lifetime. Some are based on genetics, and on how the individual is hardwired before and after birth. One dog will respond to the approach of a stranger as a life-threatening experience, while another interprets exactly the same event as a party about to happen. Both you and your dog, consciously and unconsciously, make decisions and judgments millions of times a day, about what should be filtered out, about what deserves your attention, and about how it should be evaluated. Because of that, no matter how close we are to our dogs, we’ll never really live in quite the same world as they do.
¹⁶

There’s another reason that each of us lives in our own reality, and
it’s particularly important in comparisons between different species. Not only do our brains filter out different kinds of information, they receive different information in the first place. Though we share the same planet, the sensory systems of animals vary so much that we might as well be living in different worlds. Bees can see bull’s-eye-shaped ultraviolet lines on flower petals that direct them to the pollen, when all we see is the pretty red color of the petal (and dogs can’t distinguish the red flower from the green grass because they’re red/green color-blind). In pitch darkness, bats navigate by bouncing sound waves off objects in the landscape: dogs would be using their noses to navigate, and people would be standing stock still, unable to locate much of anything at all. Some fish can sense electromagnetic currents, of which people (and, most probably, dogs) are completely unaware. These comparisons are more than just intellectually interesting in a golly-gee sort of way. They are relevant to our shared experience of emotion, because it turns out that many of our senses are closely connected to our emotions.

Like us, dogs use sight, sound, smell, taste, and touch to interpret the world around them, but, as we all know, they experience each of those senses differently from us. Vision is the most important source of information to primates, so, not surprisingly, we humans devote an inordinate amount of our sensory cortex to it. A casual look at our language illustrates the importance of sight to us. We say, “I
see
what you mean,” and
“Look!
What I’m trying to tell you is …” Vision is such an integral part of how we see the world that I’ve inadvertently referred to it twice in the last few lines: “a casual
look
at our language” and “how we
see
the world.” I didn’t use those words on purpose to make my point. I didn’t even notice that I’d written them until I reread the paragraph. I used them because that’s the way we describe the world, through the principal sensory system of primates: vision.

Dogs rely on vision too, but if a dog were writing this book surely she’d be writing “how we smell the world” and “Sniff, I
told
you never to get into the garbage when your humans are home!” We all know that a dog’s sense of smell puts ours to shame. It’s been estimated that dogs can use their noses a thousand to ten thousand times better than we
can. We may be structured to have impressive powers of abstraction and problem solving, but dogs are the ultimate smell machines. Not only do they have a nose designed to take in as many scent molecules as possible (can you move your nose from right to left?), they have a much larger surface area inside the nose to absorb scent molecules. Once the smells are received, they travel to the sensory cortex, which is proportionately huge in dogs. Their ability to experience the world through their noses means we’ll never really know what the world is like to them, because so much of what they perceive is beyond us. Think of using scent to locate the one stick, among dozens of others, that you picked up and threw for your dog last week. Your dog can do it, even after the stick has been lying in the sun and the rain for six days. Dogs are so good at finding and identifying smells that we simply can’t imagine how the world appears to them.

This difference in perception goes beyond dogs’ ability to smell tiny quantities of something that would be imperceptible to us. Dogs can distinguish
between
scents to an extraordinary degree. When you pet a damp, dirty dog, you can easily recognize the smell of “wet dog,” but you can’t separate out the smell of the water from the smell of the mud on his paws and the dander in his coat and the scent glands behind his tail. And when you walk into someone’s house for dinner and are overwhelmed with the good smell of homemade chicken soup, you smell chicken soup—but your dog smells chicken and carrots and onions, each as separate as they are when you look into the pot. If you see five objects on a blanket, your brain doesn’t perceive them as a mixture of images, it sees them as six separate things: five objects and a blanket. That’s what scientists think dogs can do with smells, separate them out, each from the others, rather than blending them together. We’re so good at separating things visually that we take it for granted, but imagine being able to do that with smells. What a different world it would be.

Comparatively pathetic though our olfactory abilities are, scent still plays an important role in our lives. Much of the information about scent that we are able to perceive is relayed not to the conscious part of our brain, but to that ancient limbic system that drives emotions, mood, and memory. That’s true for both dogs and us, and it means that the sense of smell has more effect on humans than you might think. Pheromones, a category of scent molecules that we take in but aren’t
conscious of, can change our sexual appetites, cause a man’s beard to grow faster, help mothers recognize their babies’ T-shirts merely by sniffing them, and cause men to rate women as more attractive.

In both people and dogs, the sense of smell is more closely linked with emotion than any other of the senses besides touch. Except for touch, smell is the most primitive sense, and its connections go directly to the more primitive, and emotional, parts of your brain. We’ve all had experiences in which we were flooded with emotion when we smelled the perfume worn by an old flame, or caught a whiff of Grandma’s cinnamon buns. This is because, unlike the nerves that relay information about sight and sound, the olfactory nerves go straight to the emotional part of your brain, bypassing all the other departments usually visited by our sensory perceptions before they go to the limbic system. This is true of dogs, too, and given their amazing abilities to use their noses, I often wonder if we could be using scent more effectively to communicate with our dogs.

One way in which many of us are doing that already is by using food as reinforcement in training. Food is a great motivator to both people and dogs and is a great way to teach dogs both basic obedience, like “Sit” and “Stay,” and advanced tricks, like rolling themselves up in a blanket when you say “Go to bed.” This isn’t just because food tastes good; in fact, dogs don’t have taste buds as sophisticated as ours. It’s also because food has strong odors associated with it, and the sense of smell is directly linked with the areas associated with pleasure (or disgust) in the limbic system. Indeed, the smell of food is so closely linked with primitive emotional centers that neurologists believe the limbic system first evolved as a way of evaluating whether food was good for you—or would make you sick. Good smells equaled good food, which made you feel good. Bad smells equaled bad food, which made you feel bad. Simple as that.

Now, of course, things aren’t so simple, but both you and your dog are still strongly affected by what you smell. If your dog learns to associate the good smells of food with sitting when you ask, then you’re teaching his brain to feel good when he listens to you. This is one of the reasons you can use food to get a behavior started, and then drop it out once the behavior has become a habit. You don’t need to carry dog treats around in your pocket for the rest of your dog’s life, because
you’ve wired his brain to associate listening to you with feeling good. If, on the other hand, you train primarily using force (perhaps you use a leash correction to make your dog sit), you’re missing out on a remarkable opportunity to condition a primal, positive association between obedience to you and his reaction to good food. Additionally, if you use force you’re probably stimulating the fear centers in his limbic system, so that he learns to associate you with the potential of danger. It’s a shame how common it is for people to use force and coercion on their dogs, when there’s no question that positive techniques, besides being more humane, are simply more effective.