Everyone knows someone who treats their dog like one of their children. But how closely does that relationship mirror the parent-child relationship?
That’s the question researchers at Massachusetts General Hospital set out to answer with their newest study, published in the open-access journal PLOS ONE.
“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 wellbeing of humans,” said Lori Palley, D.V.M., of the hospital’s Center for Comparative Medicine and 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.”
For the study, researchers recruited women who had at least one child between the ages of two and ten, as well as a dog that had been in the household for at least two years.
The experiment included two sessions. The first was a home visit where the women completed several questionnaires, including some related to their relationships with their child and dog. The dogs and children were also photographed in each participants’ home.
The second session took place at the Athinoula A. Martinos Center for Biomedical Imaging at the hospital, where functional magnetic resonance imaging (fMRI) — which indicates levels of activation in specific brain structures by detecting changes in blood flow and oxygen levels — was performed as the women lay in a scanner and viewed a series of photographs.
The photos included images of each woman’s own child and 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, according to the researchers. Each woman also rated several images on factors relating to pleasantness and excitement.
Of the 16 women originally enrolled, complete information and fMRI data was available for 14.
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, according to the researchers.
Areas important for functions such as emotion, reward, affiliation, visual processing, and social interaction all showed increased activity when the women viewed either their own child or their own dog, the study found.
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 woman’s own child.
The fusiform gyrus, which is involved in facial recognition and other visual processing functions, actually showed greater response to images of their dogs than images of their child, the researchers reported.
“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,” said Luke Stoeckel, Ph.D., MGH Department of Psychiatry and co-lead author of the study.
“We also observed differences in activation of some regions that may reflect variance in the evolutionary course and function of these relationships.” Stoeckel said.
“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.”
“Since fMRI is an indirect measure of neural activity and can only correlate brain activity with an individual’s experience, it will be interesting to see if future studies can directly test whether these patterns of brain activity are explained by the specific cognitive and emotional functions involved in human-animal relationships,” added Randy Gollub, M.D., Ph.D., of MGH Psychiatry and a co-author of the study.
“Further, the similarities and differences in brain activity revealed by functional neuroimaging may help to generate hypotheses that eventually provide an explanation for the complexities underlying human-animal relationships.”
The researchers note that further research is needed to replicate these findings in a larger sample and to see if they are seen in other groups, such as women without children, fathers, parents of adopted children, and with other animals.
Source: Massachusetts General Hospital