From the archive: 60 Minutes investigates whether your dog really loves you

Man's best friends have been around for thousands of years, yet there is still so much for us to learn about dogs. What are they thinking when they're with us? Do they truly love their owners? Just how smart are they?

This week, 60 Minutes correspondent Anderson Cooper continues his ongoing reporting on our favorite furry creatures and explores the evolutionary triumphs of dogs. 

Anderson Cooper last reported on dogs for 60 Minutes in 2014, in a report we called "The Smartest Dog in the World."

For the story, Cooper interviewed retired psychology professor Dr. John Pilley and his border collie, Chaser, who had been dubbed "the most important dog in the history of modern scientific research." 

Dr. Pilley had been training Chaser for up to five hours a day, five days a week, for nine years. Through her training, Chaser mastered the names of over a thousand toys, learned how to differentiate between nouns and verbs, and even landed a book deal. 

"This is a very serious science… we're not talking about stupid pet tricks," Brian Hare, an evolutionary anthropologist at Duke University, told 60 Minutes in the 2014 report. "Chaser is learning tons, literally thousands of new things by using the same ability that kids use when they learn lots of words." 

Dr. Greg Berns, a physician and neuroscientist at Emory University, has studied the human brain for decades, and was inspired by his dog to venture into learning more about the canine brain. He created an experiment to try to understand dogs' relationships with their owners, by conducting brain scans on them while they're awake, using an fMRI machine. 

While inside the scanner, the dogs were given various cotton swabs to smell. First, a swab with the sweat of a complete stranger, followed by a swab with the sweat of their owners. Berns analyzed their brain scans, and as he predicted, the part of a dog's brain that lights up when they smell their owner's scent is the caudate nucleus, or "reward center." 

According to Dr. Berns, it showed that the dog is recognizing somebody important to them. 

"We're using the brain as kind of the test to say, okay, when we see activity in these reward centers, that means the dog is experiencing something that it likes or it wants and it's a good feeling," he says.

According to Emory's Berns, human reward centers light up when we listen to a favorite song, or anticipate seeing someone we love. 

60 Minutes reported in 2014 there were over 70 million dogs in this country, more dogs than children, but there was still so much more to learn about the canine brain. And though scientists have only recently started to dig beneath the surface of our favorite pets, we can still conclude that they really are man's best friend. 

Learn more about dogs, where they come from, and what makes them so friendly, this Sunday on 60 Minutes. 

Dr. John Pilley died in 2018, just shy of his 90th birthday.