How Dogs Love Us: A Neuroscientist and His Adopted Dog Decode the Canine Brain (11 page)

McKenzie was leggy and lean, about thirty-five pounds, with a long, thin head that would easily fit in the head coil. She trotted over to me and stared long and hard. She quickly realized that I was not a herdable animal and moved on to check out Helen.

Callie zoomed over and assumed a play bow with her front legs flat and her rump in the air, tail wagging like a vibrating string. We let the two dogs off-leash and they ran around the room. Callie did orbits around McKenzie, who seemed indifferent to the newbie dog.

It was time for McKenzie’s try with the head coil. With a dog treat, Melissa had no trouble coaxing her into the coil. Nibbling the food out of Melissa’s hand, McKenzie appeared unaware of the coil altogether. In agility competition, the dogs run through a serpentine tunnel, and McKenzie was completely comfortable in an enclosed space.

After a few minutes, Melissa commanded McKenzie to lie down. “
Platz
,” she said, using the German word for “down.” Mark explained that German words are commonly used in dog training because of the popular Schutzhund competitions. These began as training programs and tests for German shepherds but evolved into a full-fledged sport involving tracking, obedience, and protection phases.

With McKenzie lying down in the head coil, Melissa backed away to the other side of the room. McKenzie didn’t budge. In fact, she stayed motionless for a solid minute. When I saw what a well-trained dog like McKenzie could do, I knew we could really do this. If the dogs would go into the head coil, they would go into the MRI.

Melissa working with McKenzie in the head coil. Callie watches from across the room.
(Bryan Meltz)

So far, Mark and Melissa had been using basic behaviorist techniques. The appeal of behaviorism in dog training is its simplicity. By making rewards like food and praise contingent on desired behaviors, dogs quickly learn what to do to get something they want. But what do dogs think of this? After all, they aren’t robots bumbling around the world, randomly doing things and finding out which behaviors result in food. Dogs show purposeful and consistent behavior whether humans are there or not. This suggests that dogs have some internal mental model of how things work in their world. It is a limited model, of course. For instance, they don’t understand technology like computers or television. But dogs do understand how to get along with each other and with other species like humans, which is not an insignificant skill, and they don’t need treats to learn how.

While McKenzie remained still in the head coil, Callie watched with rapt attention. It’s possible she was interested in only the food being handed out, but her gaze wasn’t always tracking Melissa’s hands. Callie’s eyes darted back and forth between McKenzie and Melissa. You could almost see the wheels turning inside Callie’s head as she tried to figure out what was going on.

Even though we were using basic principles of behaviorism like positive reinforcement and shaping to train the dogs to enter and lie still in the head coil, Callie made it clear that a different type of learning was going on too. She was learning by observation.

Social learning, or imitation, is an obvious feature of human behavior. We can learn a great deal simply by observing what other people do. Strangely, dogs have not been given much credit for being able to do this too. But Callie illustrated clearly what everyone with more than one dog knows: dogs learn from each other.

Although behaviorist experiments dominate the canine research literature, there have been a few experiments demonstrating social learning between dogs. An old experiment found that puppies that observe littermates pulling a cart by a string can copy that behavior. Another study showed that puppies that watched their mother, a police dog, search for narcotics did better when learning this task compared to puppies that did not observe their mother first.

Relatively little is known about the neurobiology of social learning or imitative behavior. Even in humans, we don’t know much about which parts of the brain are involved. Whether dog or human, social learning is not contingent on rewards. So why does the puppy copy its littermates and pull the cart? After all, there is no food to be gained. Maybe the Dog Project would provide the answers.

But first, we needed to train Callie and McKenzie to perform a complicated task under noisy conditions.

Over the next few weeks, Callie and I worked with the head coil at home on a daily basis. I limited the sessions to ten minutes. Mark had explained that short, daily training is much more effective than infrequent long sessions. This prevents both the dog and the handler from getting bored. Consistency is the key.

Callie learned quickly. As soon as I reached for the head coil, Callie would jump up and down to try to get in it. Once inside, she assumed the sphinx position and waited for me to give her hot dogs. Her tail never stopped wagging.

“Good coil!” I would praise. More tail wags.

The next step was to introduce the chin rest. When we scan humans, the subject normally lies on his back with his head surrounded by foam padding in the head coil. The padding makes it comfortable while also preventing head movement. But the human setup wouldn’t work for a dog. Callie and McKenzie would have to lay on their stomachs, and I doubted that either of them would want her head surrounded by foam, like Leonard did with his monkeys at Yerkes.

I didn’t yet know how we were going to solve the head movement problem. The first step, though, was to give the dogs something they could rest their heads on. Something firm, yet comfortable. My first thought was the foam used in seat cushions, so I picked up the firmest foam I could find at the fabric store, cut off a chunk, and, while Callie was relaxing on the sofa, gently wedged it under her chin. She just let her head sink into it and went to sleep. That was a good sign, but the foam compressed too much to offer enough support. We needed something firmer.

I went to the hardware store and looked at foam insulation. Too hard. I was beginning to feel like Goldilocks. For several days, I
searched in vain for something that would work. The chin rest would have to span the diameter of the foot-wide head coil. At that length, furniture foam collapsed with the slightest pressure in the middle of the span. But the materials at the hardware store were uncomfortably stiff.

The solution caught my eye in a sporting goods store. Helen and Maddy had wanted some new sneakers. While they were trying them on, I milled about, not looking for anything in particular. It was the middle of December, and the store was having a sale on summer swim gear. A stack of boogie boards was pushed into a corner with a handwritten sign: $5 each. I squeezed one. Firm, but not hard.

I took the whole stack to the register. The cashier looked at me like I was crazy.

“Science project,” I said.

At home, I used a utility knife to cut a strip of boogie board to match the inner diameter of the head coil. It made a comfortable bridge that didn’t collapse in the middle under pressure.

I got my baggie of hot dogs and approached Callie with the foam bar. She saw the treats and started wagging her tail. With her in the sphinx position on the floor, I gently pushed the foam under her chin.

“Touch,” I said, and gave her a treat.

As usual, Callie was a quick study. After a few repetitions, her head relaxed as soon as I gave the “touch” command, and I could feel the weight of her head against the foam bar. Pretty soon, I didn’t even have to cue her by pressing the boogie board against her chin. With the bar a centimeter below her chin, she would drop her head to make contact on command.

The next day, we practiced the “touch” command with Callie in the head coil. She got it. With the foam rest spanning the diameter,
Callie scooted in and stuck her paws beneath it. I said, “Touch,” and she plunked her head on the bar.

“Good girl!” I exclaimed. She just wagged her tail. I couldn’t believe how quickly she was picking this stuff up. Lyra, drooling nearby, soon learned that she too would get hot dogs by hanging around the head coil. Lyra would then start barking if she didn’t get a piece of the action. She had a sensitive stomach, though, and tended to burp if I gave her too many hot dogs.

Each day we practiced with the chin rest in the head coil, and each day Callie held her head in position for longer and longer stretches. After a week of daily sessions, I no longer needed to say the command. I would just put the head coil on the floor, and she would go right in and plop her head on the rest.

We were gradually making the task more complex for Callie and McKenzie by adding elements before the final behavior. The technique is called
backward chaining
. Once Callie had learned to go into the coil, I placed the coil inside the mockup of the MRI bore. Since Callie knew that she would be rewarded only for going into the head coil, she trotted into the tube and into the coil, after which I promptly rewarded her. Next, I raised the tube to the height of the patient table of a real MRI machine. Callie would have to be taught to go up a set of doggie steps. These were designed for dogs to walk up to the height of their owners’ beds. Since they were made entirely out of plastic, they would be safe for use next to the real MRI.

It took a couple of days to teach Callie to go up the steps. I started by placing a hot dog on each step. Callie followed the trail of meat right to the top, where I gave her excessive praise. Once she was used to the steps, I placed them in front of the elevated tube and continued the meat trail all the way to the head coil. Once she was in the tube, I ran around to the other end and pointed to the head coil. She scooted in and waited for more treats.

The last and most challenging element was the scanner noise. Andrew had already recorded the jackhammer-like sounds of the MRI in action. Initially, we focused just on getting Callie and McKenzie used to the level of ambient noise. Later, we would need to figure out the exact scanner settings for the dogs, which would result in slightly different sounds.

I started by simply playing the scanner noise at low volume through a stereo while I did the training with Callie. She quickly learned to ignore it. Each day I would increase the volume a little bit. Soon, though, it would get to a level that was unpleasant. Time to introduce Callie to the earmuffs.

Callie sporting the earmuffs and learning to use the boogie board chin rest in the head coil.
(Gregory Berns)

Human subjects wear earplugs, but I had yet to meet a dog that would let you put anything in his ears. Plus, the ear canal of a dog makes a right-angle bend. If an earplug became wedged in the canal beyond the bend, we might not be able to get it out. The only alternative was earmuffs that went over the outside of each ear. Amazingly, I discovered Safe and Sound Pets, a company that makes Mutt Muffs. The founder of the company, a pilot of small aircraft, realized the need to protect his dog’s hearing when taking him up for flights. He adapted human earmuffs to a more triangular shape that would fit most dogs’ heads. We ordered several sets in different sizes.

Callie was not so thrilled with the Mutt Muffs. It took many bits of hot dog, first for putting her nose through the loop formed by the chin strap and eventually for letting me push the earmuffs back over her head. Even then, she would paw them off right away. I didn’t push her. With Mark’s advice, I gradually lengthened the time she had to wear them before giving her a piece of hot dog. Pretty soon, Callie would leave the earmuffs on, trot up the steps into the tube, and place her head on the chin rest in the head coil.

Everything was going faster than I had anticipated. Melissa was working with McKenzie in parallel; unsurprisingly, they made even quicker progress. In fact, the training was going so well, I hadn’t even stopped to ponder what we were doing to their brains, which, after all, was the subject of the Dog Project.

Even though we were using basic behaviorist principles to shape a complex behavior in the dogs, it couldn’t explain what the dogs thought of all this. If we cared about just behavior, the reason a dog did something or what she thought wouldn’t matter. But if we got to the point of actually scanning their brains, the dogs’ motivations
could have a big impact on what we found. Doing something for food would look very different from doing something for social praise or, dare I say, love.