Source: Clipart division of Vital Imagery

While I was standing in line for a cup of coffee I overheard a snippet of conversation between the two women in front of me.

"So what brought you to the mall today?" the first asked.

"Just buying a new collar for my baby. Here's a picture that I took of her on the weekend, "she said as she held up her smart phone to show a picture of an amber colored spaniel flanked by two young children. Since the two kids were not wearing collars or other kinky accoutrements, I assumed that her phrase "my baby" was meant refer to her dog.

Many dog owners feel that their dogs are part of their families, much like their children, and some even refer to themselves as "pet parents" which reflects the similarity in the affection that they feel for both their dogs and their kids. The interesting fact is that some recent research suggests that your brain seems to be wired to react as if that were true. The most recent confirmation of this appears in a study published in the journal PLOS ONE*. A research team headed by Luke Stoeckel at Massachusetts General Hospital investigated differences in brain activity when women viewed pictures of their dogs, their own children, and also unfamiliar dogs and children. What they found suggests that the bond between humans and dogs tugs at the same heartstrings — or at least stimulates the same brain centers — as the bond between a mother and her child.

The experimenters had an expectation that this might be the case because of earlier research that looked at changes when people interact with dogs. In the previous studies the of was measured. Oxytocin is a hormone which many researchers believe is associated with social interactions and affection. Some have gone as far as calling it the "love hormone". What was found was that the levels of oxytocin went up in human beings when they engaged in friendly interactions with their dogs which is a clear physiological sign of affection (to read more about this click here).

In this new study the researchers collected data from 14 women who had at least one child aged 2 to 10 years old and one pet dog that had been in the household for two years or longer. The women were first surveyed about their relationship to their children and their pet, and then tested using functional magnetic resonance imaging (fMRI) which is a technique that indicates the level of activity in specific brain structures by detecting changes in blood flow and oxygen levels. As the women laid in the scanner they were shown a series of test photographs of kids and dogs. It turns out that many of the areas of the brain that are involved in emotion and reward processing (such as the amygdala, the medial orbitofrontal cortex, and dorsal putamen) were activated when mothers viewed pictures of their own children or the family dog, but not when they viewed photos of unfamiliar dogs and children.

Still, as is usually the case with studies of this sort, the imaging results add some interesting nuances to the human-dog relationship. One example of this is that a brain region known as the fusiform gyrus was activated more when mothers looked at their dogs then when they looked at their kids. The researchers suggest that this might be because this area is involved in face processing. "Given the primacy of language for human-human communication, facial cues may be a more central communication device for dog-human interaction," the authors write.

On the other hand, two areas in the midbrain (the substantia nigra and ventral tegmental area) were more active when mothers looked at their children but not when they looked at their dogs. These brain areas contain high concentrations of , oxytocin, and vasopressin, all of which are chemicals that are involved in reward and bond formation (typically mother-child and romantic bonds). This could mean that these areas are crucial for forming pair bonds within our own species but not so relevant for the bonds we form with . This makes sense if we consider things in terms of evolutionary significance. It would be reasonable for the brain to have at least one area which is tied to certain species-specific relationships — ones that should be maintained at all cost — such as that between a person and their child or their mate.

The authors conclude by saying "These results demonstrate that the mother-child and mother-dog bond share aspects of emotional experience and patterns of brain function, but there are also brain-behavior differences that may reflect the distinct evolutionary underpinning of these relationships."

So in effect, our dogs are not our children, but according to our brain responses they are close enough in terms of evoking our affection so that we should not look down on people who refer to their pets as their "babies".

Stanley Coren is the author of many books including: The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; The Left-hander Syndrome

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission

* Data from: Stoeckel LE, Palley LS, Gollub RL, Niemi SM, Evins AE (2014) Patterns of Brain Activation when Mothers View Their Own Child and Dog: An fMRI Study. PLoS ONE 9(10): e107205. doi:10.1371/journal.pone.0107205