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.

I had the nagging feeling that the ease with which dogs slip into human lives could not be fully explained by behaviorist theories. For dogs to do what they do, they must have a rich inner life that goes beyond a chain of actions resulting in food. Dogs must have a rich mental model of their environment. As highly social animals, these mental models are likely to be weighted heavily toward social relationships. Not just dominance and subordination, but more fluid models of how they should behave with members of their household, either dog or human, and how these interactions will affect their current state of well-being.

It makes you wonder who is training whom. Skinner and Pavlov were partly right. Their principles are highly effective in training behavior. But they studied animals in a laboratory—a place where the human controls pleasure and pain. Dogs in their native environment—the human household—interact with us in a much more natural way. There is give-and-take, and testing, on both sides.

10

The Stand-In

WITH CALLIE AND MCKENZIE making rapid progress in their training, we would soon be ready to make the jump to the real scanner. Although the mock head coil and tube were good facsimiles of the MRI, they weren’t the real things. There was no way to simulate the smells and sounds of the hospital, for instance. We wouldn’t know how the dogs would react until we actually brought them there.

The initial introduction to the real MRI would be critical. Dogs can form negative imprints of environments based on one event: a loud noise such as a slamming door, an encounter with someone who doesn’t like dogs. Any of these could permanently affect a dog’s impression of the MRI. If that happened, and the dog didn’t want to go near the scanner as a result, all the training we’d done would have been wasted.

Mark and I were particularly concerned about noise. The MRI scanner makes a wide range of sounds. The magnetic field is always on, and this requires constant tending by an array of devices, like the pumps that circulate chilled water around the magnet. When you enter the room, the first thing you hear is the heartbeat of the circulation pumps. If you listen carefully, you will also hear the machine breathing, the sound of the “cold-head”—a compressor that keeps the helium under pressure.

How would the dogs react to this living machine?

When scanning a subject, MRIs are loud. Depending on the particular settings, an MRI can reach nearly 100 decibels. Every 6 decibels means a doubling in the sound pressure. Normal conversation is about 60 decibels. Busy traffic, 80 or 90. A jackhammer is 100. Hearing damage for humans begins at around 120 decibels, equivalent to a jet engine at a hundred meters. Nobody knows at what level hearing damage occurs in dogs, but one point of reference is hunting. The report of a hunting-caliber bullet is 170 decibels, and hearing loss after repeated gunshot exposure is a well-known phenomenon in both hunting and military working dogs.

Earmuffs can cut sound levels by 20 or even 30 decibels, so assuming that a dog’s hearing is more sensitive than that of a human, Callie and McKenzie would be fine as long as they wore ear protection.

The loudness of the MRI wasn’t the whole story, though. The type of sound made could also have a big effect on the dogs. The MRI makes different types of sounds depending on the type of brain scan being performed. Some scans sound like a swarm of bees, while other scans are like the klaxon of a submarine preparing to dive. The specific sound depends on dozens of parameters that are programmed for each scan. These parameters indicate how many slices through the brain will be made, how thick they will be, and whether they should focus on gray matter (the neurons) or white matter (the connections between neurons) or on changes in blood flow like we do in fMRI.