The Scent That Brings Dogs the Most Pleasure

Dogs Prefer Human's Scent

Story at-a-glance -

  • A recent study suggests dogs prefer the scent of their special humans to even the scent of other dogs.
  • The study involved a dozen dogs trained to remain perfectly still in an fMRI scanner. While in the scanner, the dogs were presented with swabs containing the scent of a familiar and an unfamiliar person, a familiar and unfamiliar dog, and their own scent.
  • Pleasure centers of the dogs’ brains were most highly activated when presented with the swab containing their human’s scent. This suggests not only that dogs react positively to the scent of their people, but also that the scent lingers in a dog’s mind.
  • The dogs showing the most positive response to human smells were those with training as service or therapy dogs.
  • The researchers believe this and other fMRI studies of the canine brain could at some point help select the best candidates for service and therapy dog training.

By Dr. Becker

Here’s a neat new scientific finding for dog lovers – did you know your scent activates the pleasure centers in your pet’s brain? According to neuroeconomist Gregory Berns of Emory University, who led the study, it’s similar to the way the human brain responds to the perfume or cologne of a loved one.

Berns is known for his ability to train dogs to sit perfectly still for fMRI (functional magnetic resonance imaging) tests, which affords him the ability to examine the inner workings of the canine brain. Whereas an MRI takes images of the brain, an fMRI measures the activity of the brain’s nerve cells.

Berns and his team started their dog studies a few years ago to learn more about what dogs are thinking and experiencing. The researchers were especially interested in studying the areas of a dog’s brain that are similar to areas in the human brain, for example, areas associated with reward.

Dogs Are Given a Whiff of This and a Whiff of That While Undergoing Brain Scans

In his latest study, which is the first brain-imaging study of canines responding to the smells of other dogs and people,1 Berns enlisted the help of 12 dogs of various breeds, including five service and therapy dogs and his own dog, Callie. All the dogs were trained to hold perfectly still in the fMRI machine. The goal was to use the technology to measure the dogs’ response to biological odors.

While being scanned, the dogs were presented with gauze pads containing five different odors, including the scent of a familiar human (someone from their household, but not their owners, who were their handlers during the experiment), an unfamiliar human, a canine housemate, an unfamiliar dog, and their own scent. The scents were swabbed from the rear/genital areas of the dogs, and the armpits of the humans. The familiar humans were typically the husbands of the dogs’ owners, who were asked not to bathe or use deodorant for 24 hours before they were swabbed.

(Needless to say, the humans involved in the experiment weren’t too thrilled with the whole don’t-bathe-swab-your-armpit thing!)

The Result: Dogs’ Brains Are Most Activated, and Pleasantly So, by the Scent of a Familiar Human

Berns and his colleagues discovered that an area of the brain related to positive expectations, the caudate nucleus, was most triggered by the scent of a familiar person. This indicates that dogs are not only able to pick out the scent of their owners and have a positive response, but also that a familiar human scent remains in a dog’s mind.

In an interview with Discovery News, Berns said:

“It’s one thing when you come home and your dog sees you and jumps on you and licks you and knows that good things are about to happen. In our experiment, however, the scent donors were not physically present. That means the canine brain responses were being triggered by something distant in space and time.”2

The researchers also learned from the fMRI scans that the dogs didn’t respond to any of the other four scents in a significant way, though the familiar dog smell came in second.

The dogs in the study that were trained as service or therapy dogs showed the most positive response to human smells. This could be due to genetics, or a more highly developed connection to people resulting from their specialized training.

“While we might expect that dogs should be highly tuned to the smell of other dogs, it seems that the ‘reward response’ is reserved for their humans. Whether this is based on food, play, innate genetic predisposition or something else remains an area for future investigation,” Berns said.

fMRI Studies May One Day Help in the Selection of the Best Candidates for Service and Therapy Dog Training

Berns thinks these and other fMRI study results may help us learn more about working dogs, including service dogs. It’s possible that scanning service dog candidates for specific heightened brain responses may point out the animals most likely to be successful in the role. Training service dogs is very expensive, and less than half (30 to 40 percent) of those trained are ultimately suitable to be placed.

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