By scanning the brains of mothers who are also dog owners, researchers show that babies and pets evoke similar responses in brain areas linked to emotion and reward. The study, published in PLOS ONE this week, suggests that dog owners really do love their pups like their babies.

So, all joking aside, how closely does the human-pet relationship mirror the parent-child bond? A team led by Massachusetts General Hospital’s Lori Palley and Luke Stoeckel investigated differences in how certain brain structures are activated when women viewed images of their children and of their dogs. "Levels of neurohormones like oxytocin -- which is involved in pair-bonding and maternal attachment -- rise after interaction with pets, and new brain imaging technologies are helping us begin to understand the neurobiological basis of the relationship, which is exciting," Palley says in a news release.

The team recruited 16 women with at least one child aged two to 10 and one pet dog who’s been part of the household for at least two years. Participants completed several questionnaires asking about their relationships with their kid and their pooch, who were both photographed in their own homes.

Then researchers used functional magnetic resonance imaging (fMRI) -- which measures brain activity based on blood flow and oxygen levels -- to scan the brains of the women as they viewed photos of their children and their dogs. These pictures were alternated with those of unfamiliar children and dogs. Each recruit also rated images based on things like pleasantness and excitement.

The team found striking similarities and differences in how various regions reacted. Brain areas linked to emotion, reward, affiliation, visual processing, and social interaction all showed increased activity when they viewed either their own child or dog, but not with unfamiliar kids and hounds.

The substantia nigra and ventral tegmental area -- two midbrain regions important to bond formation -- activated only in response to images of their children. On the other hand, the fusiform gyrus, which is involved in visual processing functions like facial recognition, displayed greater response to puppy pics than baby photos. Additionally, the nucleus accumbens, which played a pair-bonding role in previous human and animal studies, showed greater deactivation when mothers viewed images of their dogs -- instead of their children, which was unexpected.

“We think the greater response of the fusiform gyrus to images of participants’ dogs may reflect the increased reliance on visual than verbal cues in human-animal communications,” Stoeckel explains. Humans communicate primarily through language, rather than the facial cues dogs might look for. The differences in activation may reflect the varying evolutionary course and function of these relationships.

While the study was small and fMRI is only an indirect measure of brain activity, Stoeckel adds, there appears to be a common brain network important for pair-bond formation and maintenance that’s activated in mothers viewing images of their babies, furry and otherwise.

Image: Christian Collins via Flickr CC BY-NC-SA 2.0