Dog owners will often refer to their 'babies' - but researchers have found they really do think of their pets as children.
Researchers analysed women who had both a child and a dog - and found showing pictures of them elicited the same response in the brain.
They even found some areas of the brain responded more to pictures of their dog than their children.
'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 of Massachusetts General Hospital (MGH), who led the research.
HOW THEY DID IT
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 participants' home.
Functional magnetic resonance imaging (fMRI) – which indicates levels of activation in specific brain structures by detecting changes in blood flow and oxygen levels – was then performed as participants lay in a scanner and viewed a series of photographs.
'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.'
Their report is being published in the open-access journal PLOS ONE.
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 participants' home.
Functional magnetic resonance imaging (fMRI) – which indicates levels of activation in specific brain structures by detecting changes in blood flow and oxygen levels – was then performed as participants lay in a scanner and viewed a series of photographs.
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, co-lead author of the PLOS ONE report.
'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.'
