Monday, October 27, 2014

Furbabies vs human babies: what do functional MRIs say?

Do photos of human babies trigger similar responses in our brains to photos of companion animals? (NB I borrowed this human baby for the photo!)
The expression “furbaby” has crept into the common parlance, and I must confess to using it in a sentence or two as shorthand to describing the human-animal bond, at least as it is manifested in certain contexts (my own included).

The practice of adopting and caring for other species, like dogs and cats, is a common human behaviour across cultures and places. It has been referred to as “alloparenting”. Alloparenting occurs when individuals other than the biological parents of someone play a parenting role toward that someone. For example, if your grandparents raised you, they were alloparenting. Pet owners are not a homogenous group and the human-animal bond is far from homogenous, so the term “alloparenting” doesn’t apply to every human-companion animal situation.

But, aside from that, companion animals bother some scientists. What possible evolutionary benefit, they ask, is there in looking after someone else’s baby? Why invest time and energy in providing for another being? Many studies looking at the potential benefits of pet ownership are prefaced by such a concern. What’s in it for us?

Bring on the fMRI, I can feel most of my brain light up at the site of Phil.

One hypothesis that has gathered much traction is that “happy hormones” such as oxytoxin, beta-endorphin, prolactin, beta-phenylthylamine and dopamine are increased in positive interactions with pets. They’re also “bonding” hormones in people.

So are we bonding to pets the way we bond to babies?

A team of researchers from Massachusetts General Hospital and Harvard Medical School got together to work out if the attachment looks the same on the brain level (see the full paper here).

They compared interviews and functional magnetic resonance imaging (fMRI) patterns in mothers viewing photographs of their own child and their own pet dog, as well as an unfamiliar child and unfamiliar dog.

The mothers were 22-45 years old, had at least one child who was 2-10 years old, had at least one dog for at least two years, and were generally healthy. A complete data set was collected from 14 participants – so we’re talking a reasonably small number here.

In interviews, mothers reported images of their own child and dog as eliciting similar levels of excitement/arousal and pleasantness (valence), although they were bigger differences in the response to own vs unfamiliar child than there were to own vs unfamiliar dog.

The pleasantness a mother felt when seeing her own dog’s photo was positively correlated to how attached she was to her own dog, which makes sense.

Viewing photographs of their own child was associated with activity in the midbrain (specifically the ventral tegmental area/substantia nigra, an area rich in dopamine, oxytocin and vasopressin). This area of the brain is thought to be critical in reward/affiliation – but it was NOT activated by images of the dog.

Viewing photographs of their own dog was associated with a more posterior cortical brain activation pattern involving fusiform gyrus (usually responsible for visual processing, social cognition). The authors speculate that maybe we find dogs harder to read so there is a lot more processing of visual cues.

The amygdala, believed to be an important region for bonding, was activated by both familiar child and familiar dog images.

So the researchers conclude that mother-child and mother-dog bonds are same-same but different: they share aspects of emotional experience and patterns of brain function (at least as apparent on fMRI), but there are also differences in the brain’s activity which might reflect differences in these relationships. It doesn't quite solve the mystery of "alloparenting" but provides another piece of information in the puzzle.

On a related note, if you’ve ever contemplated introducing a human baby where you have a pre-existing furbaby, check out this post.