For the past two years, my colleagues and I have been training dogs to go in an MRI scanner — completely awake and unrestrained. Our goal has been to determine how dogs' brains work and, even more important, what they think of us humans.
Now, after training and scanning a dozen dogs, my one inescapable conclusion is this: Dogs are people, too.
From the beginning, we treated the dogs as persons. We used only positive training methods. No sedation. No restraints. If the dogs didn't want to be in the MRI scanner, they could leave. Same as any human volunteer.
My dog Callie was the first. Rescued from a shelter, Callie was a skinny black terrier mix, what is called a feist in the southern Appalachians, from where she came.
We started teaching Callie to go into an MRI simulator that I built in my living room. She learned to walk up steps into a tube, place her head in a custom-fitted chin rest, and hold rock-still for periods of up to 30 seconds. Oh, and she had to learn to wear earmuffs to protect her sensitive hearing from the 95 decibels of noise the scanner makes.
For our first tests, we measured Callie's brain response to two hand signals in the scanner. In later experiments, we determined which parts of her brain distinguished the scents of familiar and unfamiliar dogs and humans. Soon, the local dog community learned of our quest to determine what dogs are thinking. Within a year, we had assembled a team of a dozen dogs who were "MRI-certified."
Although we are just beginning to answer basic questions about the canine brain, we cannot ignore the striking similarity between dogs and humans in both the structure and function of a key brain region: the caudate nucleus.
Rich in dopamine receptors, the caudate sits between the brainstem and the cortex. In humans, the caudate plays a key role in the anticipation of things we enjoy, like food, love and money. But can we flip this association around and infer what a person is thinking just by measuring caudate activity? It is not usually possible to pin a single cognitive function or emotion to a single brain region, but the caudate may be an exception. Specific parts of the caudate stand out for their consistent activation to many things that humans enjoy.
In dogs, we found that activity in the caudate increased in response to hand signals indicating food. The caudate also activated to the smells of familiar humans. And in preliminary tests, it activated to the return of an owner who had momentarily stepped out of view.
Do these findings prove that dogs love us? Not quite. But many of the same things that activate the human caudate, which are associated with positive emotions, also activate the dog caudate. The ability to experience positive emotions, like love and attachment, would mean that dogs have a level of sentience comparable to that of a human child. Dogs, and probably many other animals (especially our closest primate relatives), seem to have emotions just like us.
© 2013 New York Times