Photograph by Suzanne Kreiter, The Boston Globe via Getty
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Sari Sherman trains with her dog Molly at the National Education for Assistance Dog Services in Princeton, Massachusetts, on October 23.
Photograph by Suzanne Kreiter, The Boston Globe via Getty

Dog Brains Link Pleasure With Owner’s Scent

An owner’s scent activates the parts of a dog‘s brain associated with pleasure, a new brain-imaging study says.

A dog encountering its owner’s smell could feel in some way like a person reacting to the perfume or cologne of a loved one, according to study leader Gregory Berns, a neuroeconomist at Emory University in Atlanta.

For his research, Berns trains dogs to sit still during functional magnetic resonance imaging (fMRI), allowing him to look into the minds of man’s best friends. Compared with MRI, which takes images of the brain, fMRI measures the activity of the brain’s nerve cells. (Watch a video of Berns at work here.)

Though people and dogs have been bonding for 40,000 years, scientists still have trouble interpreting their barks, wags, and other behaviors.

“We started the dog project about three years ago to get around this problem that we really don’t know what dogs are thinking or what they’re experiencing,” said Berns, whose study appeared March 6 in the journal Behavioural Processes.

Specifically, Berns and his team studies areas of the dog brain that are similar to areas in our brains, such as structures associated with reward. (Related: “OCD Dogs, People Have Similar Brains; Is Your Dog OCD?“)

Scent of a Human

In the new study, Berns and his team performed fMRI on 12 dogs, including 5 service or therapy dogs and his own dog, Callie, to test their response to biological odors.

The experiment dogs were presented with five scents on gauze pads: a familiar human, an unfamiliar human, a dog that lived in their household, an unfamiliar dog, and their own scent.

The researchers found that the dogs’ caudate nucleus, an area of the brain associated with positive expectations, was most activated by the scent of the familiar person. (Read “How to Build a Dog” in National Geographic magazine.)

This suggests not only that dogs can discern their familiar humans and have a positive expectation about them, but also that these humans’ smells linger in a dog’s mind.

The brain scans showed that the dogs didn’t respond to the other four scents in a meaningful way, though the familiar-dog smell came in second.

Sniffing Out Better Service Dogs

The research may also help people better understand working dogs, including service dogs, Berns noted.

For instance, future research with the fMRI-trained dogs will focus on hand signals and whether the dogs’ reward responses vary according to who gives those signals. This question is especially significant when it comes to service dogs, which “need to be tuned in to their one person,” Berns said. (Related: “Dogs’ Brains Reorganized by Breeding.”)

What’s more, scanning potential service dogs for enhanced brain responses may pinpoint canines that are most up to the task. Training service dogs is very expensive, he said, and only 30 to 40 percent of those trained are placed with a person.

Overall, Berns believes the dogs experience something akin to pleasure when they smell their owners. (Read “Minds of Their Own” in National Geographic magazine.)

“To the critics out there, it’s always difficult to prove that an animal is feeling something like a human emotion—although I think they do.”

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