The Neurobiological Basis of a Human-Pet Relationship

My wife adores our cats. Now, I’m not a cat person, but my wife loves them. In fact if we had children and someone held a gun to her head and said choose between the kid or the cats, there would likely be an uncomfortable amount of time before a response. The big question is, why do we love animals like we do our own children? Well a small study helps try to answer this complex question by investigating differences in how important brain structures are activated when women view images of their children compared to images of their own dogs.

“Pets hold a special place in many people’s hearts and lives, and there is compelling evidence from clinical and laboratory studies that interacting with pets can be beneficial to the physical, social and emotional well being of humans,” says Lori Palley, co-lead author of the report.

“Several previous studies have found that 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.”

In order to compare patterns of brain activation involved with the human-pet bond with those elicited by the maternal-child bond, the study enrolled a group of women with 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.

Participation consisted of two sessions, the first being a home visit during which participants completed several questionnaires, including ones regarding their relationships with both their child and pet dog. The participants’ dog and child were also photographed in each participant’s’ home.

The second session involved functional magnetic resonance imaging (fMRI) — this imaging technique indicates levels of activation in specific brain structures by detecting changes in blood flow and oxygen levels –which was performed as participants lay in a scanner and viewed a series of photographs. The photos included images of each participant’s own child and own dog alternating with those of an unfamiliar child and dog belonging to another study participant.

After the scanning session, each participant completed additional assessments, including an image recognition test to confirm she had paid close attention to photos presented during scanning, and rated several images from each category shown during the session on factors relating to pleasantness and excitement.

Of 16 women originally enrolled, complete information and MR data was available for 14 participants. The imaging studies revealed both similarities and differences in the way important brain regions reacted to images of a woman’s own child and own dog. Areas previously reported as important for functions such as emotion, reward, affiliation, visual processing and social interaction all showed increased activity when participants viewed either their own child or their own dog.

A region known to be important to bond formation – the substantia nigra/ventral tegmental area (SNi/VTA) – was activated only in response to images of a participant’s own child. The fusiform gyrus, which is involved in facial recognition and other visual processing functions, actually showed greater response to own-dog images than own-child images.

“Although this is a small study that may not apply to other individuals, the results suggest there is a common brain network important for pair-bond formation and maintenance that is activated when mothers viewed images of either their child or their dog,” says Luke Stoeckel, PhD, and co-lead author.

“We also observed differences in activation of some regions that may reflect variance in the evolutionary course and function of these relationships. For example, like the SNi/VTA, the nucleus accumbens has been reported to have an important role in pair-bonding in both human and animal studies. But that region showed greater deactivation when mothers viewed their own-dog images instead of greater activation in response to own-child images, as one might expect. 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.”

The investigators note that further research is needed to replicate these findings in a larger sample and to see if they are seen in other populations — such as women without children, fathers and parents of adopted children — and in relationships with other animal species. Combining fMRI studies with additional behavioral and physiological measures could obtain evidence to support a direct relationship between the observed brain activity and the purported functions. Which may help in unraveling the mysteries of the brain.

Sources: 
Stoeckel, L., Palley, L., Gollub, R., Niemi, S., & Evins, A. (2014). Patterns of Brain Activation when Mothers View Their Own Child and Dog: An fMRI Study PLoS ONE, 9 (10) DOI: 10.1371/journal.pone.0107205