Does your dog love you more than her dinner bowl?

As the first domesticated animal species, dogs have a longstanding reputation as man’s best friend. Could the motivation behind that friendship be more self-serving than it appears? 

A recent study published in the journal Social, Cognitive, and Affective Neuroscience investigates whether dogs are really as loyal as they’re said to be, or whether their relationship with humans is motivated primarily by food.

"Dogs are hypersocial with humans," lead author Gregory Berns, a psychologist at Emory University, said in a press release, "and their integration into human ecology makes dogs a unique model for studying cross-species social bonding."

Dog owners are well aware of their pets' response to food motivators, and previous experiments have confirmed that canines are highly motivated by food: Ivan Pavlov’s famous early 20th-century experiment, for example, in which he trained dogs to salivate at the sound of a bell by using food as a reward.

Outside of a lab, however, humans training their pets often combine social rewards like praise or play with food rewards, making it difficult to determine which one motivates dogs the most. Dr. Berns's team wanted to determine just how much dogs are motivated by food, and how much they are motivated by intrinsic devotion to humans.

"One theory about dogs is that they are primarily Pavlovian machines: They just want food and their owners are simply the means to get it," Berns said. "Another, more current, view of their behavior is that dogs value human contact in and of itself."

In order to test these theories, researchers trained dogs to associate three different toys with different outcomes: a hairbrush represented no reward, a pink truck represented a food reward, and a blue knight brought praise from the pooch’s owner.

After completing the association training, researchers hooked the dogs up to an fMRI machine and watched their responses to each of the toys, through 32 trials per toy. Next up, they were given a behavioral test. The pups reentered a maze room they'd already been trained to navigate, and found a choice of two paths: one ended with a bowl of food, and one ended with the dog’s owner, who sat with their back to the maze. If the dog chose to go to their owner, the owner praised it.

Thirteen dogs completed both experiments, just two were "real chowhounds," Berns says, meaning they appeared to prefer food over an interaction with their owner. The majority seemed to like both equally, or to prefer the praise. 

Moreover, researchers found that dogs responded to the maze similarly to how they responded to the toy association experiment, which led them to conclude that dogs have individual personalities shaping their responses to stimuli. While most dogs alternated between choosing the food and choosing their owner’s praise, the dogs who had the strongest positive response to praise in the toy experiment chose to go to their owners 80 to 90 percent of the time.

"Dogs are individuals and their neurological profiles fit the behavioral choices they make," says Berns, whose team is now exploring dogs' ability to process human language. 

So what does this study mean for you and your dog? Fido probably likes you just as much, if not more, than he likes food. 

But the findings may come in useful for hard-working dogs, as well. 

"A dog with high preference for social reward might be best suited for certain therapeutic or assistance jobs, while a dog with less of a neural preference for social reward might be better suited for tasks that require more independence from humans, like search-and-rescue dogs or hearing-assistance dogs," the study notes.