Most dog owners would give anything to know what their pet thinks about them - and a new study has set out to answer this burning question.
Animal cognition scientists at Emory University, in Georgia, America, trained a group of dogs to lie down long enough to send them into an MRI machine to figure out how they perceive their owners.
Using fMRI (functional magnetic resonance imaging), the team measured the dogs' neural responses to the smell of people and dogs, both familiar and unknown to them.
As dogs navigate the world through smell, it is thought a person's scent could offer a greater insight into their social behaviour with humans.
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The study, written by Gregory Berns, Andrew Brooks and Mark Spivak, reads: "Understanding dogs' perceptual experience of both conspecifics and humans is important to understand how dogs evolved and the nature of their relationships with humans and other dogs.
"Olfaction is believed to be dogs’ most powerful and perhaps important sense and an obvious place to begin for the study of social cognition of conspecifics and humans."
The team presented five scents to 12 dogs of various genders, ages and breeds. These included their own smell, a familiar human, a strange human, a familiar dog and a strange dog.
They aimed to discover how the dogs would react upon smelling the scent and whether their "primary association to reward" would activate more towards their favourite humans.
The study continues: "The main result is that while the olfactory bulb/peduncle was activated to a similar degree by all the scents, the caudate was activated maximally to the familiar human.
"Importantly, the scent of the familiar human was not the handler, meaning that the caudate response differentiated the scent in the absence of the person being present.
"The caudate activation suggested that not only did the dogs discriminate that scent from the others, they had a positive association with it.
"This speaks to the power of the dog's sense of smell, and it provides clues about the importance of humans in dogs’ lives."
With their research showing how a dog's brain lights up when smelling a familiar human, owners can rest easy knowing their dog loves them and experiences positive emotions when they're around.
However, the findings made the team question the origin of dogs' social flexibility, leaving them to wonder whether the caudate response the result of selective breeding or social environment.
"Selective breeding may have created a natural interspecies bond that is stronger than the dogs’ innate intraspecies bond," the study reads.
"Nine of the 12 dogs were purebred, of which four were from service-dog programs, and the other five were specifically bred to perform in conformation or working shows.
"Three of the dogs were mixed breeds that were adopted from rescue agencies or shelters. Most likely these dogs emanated from accidental, not purposeful, breeding.
"Alternatively, the caudate response to familiar humans may be a result of the nurturing environment in which the dogs were raised. All of the dogs were family pets and had been raised by humans since they were puppies.
"However, because the service dogs were both bred for this job and raised with intense human contact from a young age, this may explain the greater response of their caudates to human scents.
"Because the same result was obtained in the analysis of the differential response to hand signals indicating the presence or absence of food reward, the greater caudate responsiveness of the service dogs appears to be a stable trait of the dogs.
"However, we cannot distinguish the respective roles of heredity from environment in this regard, or that the difference in service dogs may be due to the small sample size.
"But even without interpreting the dog's subjective experience, it is significant that the caudate was more active to the smell of a familiar human than a familiar dog."
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