NEW YORK - Brain scans showing that human responses to our dogs are not unlike those evoked by our children suggest a deep evolutionary bond, according to a recent study.
The findings are in line with dogs' special place as mankind's best friend, and may support the benefits of dog-assisted therapies, researchers say.
"The overlap says a lot about how similar the relationships could be, but we're only speculating," said Lori Palley, who led the study with Luke Stoeckel at Massachusetts General Hospital in Boston.
The experiments involved 14 mothers ages 22 to 45, each with at least one child between two and 10 years old and one dog owned for at least two years.
Each woman underwent magnetic resonance imaging, or MRI, (which measures brain activity by detecting changes in blood flow) and viewed images of her own child and dog as well as unfamiliar children and canines.
Afterwards the mothers took an 11-question multiple choice test that asked about the hair colour of their child and dog, the number of pictures viewed and had the women rate images based on their emotional value.
"Basically we compared the human-pet bond with that of the maternal-child relationship and analysed patterns of brain activity when moms viewed the images with the aim of understanding what areas might be common and what areas distinct," said Palley, who is assistant director of Veterinary Services at the hospital's Center for Comparative Medicine.
When mothers looked at pictures of their own kids and their own dogs, areas of their brains associated with emotion, reward, visual processing and social cognition showed increased activity on the scans.
But there was more brain activity in areas involved in bond formation (typically maternal-child and romantic bonds) when mothers viewed their own children versus their own dogs, the study team reports in the journal PLOS ONE.
"What's really interesting about this is we suspect that perhaps there is some evolutionary significance to that," said Palley. "It would make sense that would be an area where you would want it to be kind of specific for relationships that should be sustained at all cost."
In all cases, brain responses were strongest when the women viewed their own child versus one they didn't know, and their own dog versus an unknown dog.
An area of the brain involved in visual and social processing was more active when moms looked at their pets than at their kids.
"I think perhaps we process the dog's face differently than we process the human face, but we don't know that. We'd actually have to do more work to look at that area more specifically to determine exactly what this finding means," Palley said.
She added that she was interested in the health benefits of pet ownership and animal-assisted therapy and, in this study, wanted to examine the science involved.
"How do you better understand the human animal-connection or figure out for whom perhaps pet or animal assisted-therapy would be more beneficial," Palley said. "What is going on in the brain?"
Palley cautioned that the results would need to be replicated in a larger study involving other people, including women without kids and men.
The findings help support what many researchers already suspected, according to Alan M. Beck, professor and director of the Center for the Human-Animal Bond at Purdue University School of Veterinary Medicine.
"We have a long history, a kind of affiliation," said Beck of the relationship people have with dogs. "Dogs learn from us, we learn from dogs, so it's not surprising that even brain activity would show how inborn it is."
Beck, who has done a number of studies and written extensively on human-animal bonds, also said the study might add some scientific legitimacy to pet ownership.
"It was kind of cool," Beck said of the study. "It's just one of the tools that allows a better understanding that this is a true biological/species behaviour as opposed to something we've learned from our mothers… to be nice to animals."
The study might also help show that people who love pets can also love people.
"We are wired to some degree to be nurturers of critters that evoke a desire of being nurtured and cared for," Beck said.