Your pet dog's brain carries your odour like a perfume, a new study suggests.
Researchers found that canines' brains produce a reward signal more strongly in the presence of familiar humans than they do in the presence of familiar dogs or unfamiliar humans.
"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," said lead researcher Gregory Berns, director of Emory University's Centre for Neuropolicy.
"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. It shows that dogs' brains have these mental representations of us that persist when we're not there," said Berns.
When humans smell the perfume or cologne of someone they love, they may have an immediate, emotional reaction that's not necessarily cognitive, Berns noted.
"Our experiment may be showing the same process in dogs. But since dogs are so much more olfactory than humans, their responses would likely be even more powerful than the ones we might have," Berns said.
Berns led a team that captured the first brain images of alert, unrestrained dogs, using harmless functional magnetic resonance imaging (fMRI), setting the stage for exploring the neural biology and cognitive processes of man's best friend.
He has shown that dogs have a positive response in the caudate region of the brain when given a hand signal indicating they would receive a food treat, as compared to a different hand signal for "no treat."
In humans, the caudate region is associated with decision-making, motivation and processing emotions.
"Olfaction is believed to be dogs' most powerful and perhaps important sense, making it an obvious place to explore canine social cognition," said researcher Mark Spivak.
An area of the canine brain associated with reward responds more strongly to the scents of familiar humans than it does to the scents of other humans, or even to those of familiar dogs, researchers said.
The dogs in the experiment that had received training as service/therapy dogs showed greater caudate activation for the scent of a familiar human compared with the other dogs.
It is unclear whether this difference was due to genetics or had simply been fostered through the service/therapy training, said researchers.
The study was published in the journal Behavioural Processes.