Thank Good Mothers for Licking Their Little Rats

Published by —  On Mother’s Day, let us heartily commend those profoundly affectionate moms, who don’t hover, but do console.

When a character flaw appears in ourselves or others, our instinct is to blame Mom.  I know that’s my own boys’ working theory.  But, as it turns out, hard science is on their side.

Researchers who work with lab rats have long known that some rats are cooperative and social while others are nasty and aggressive.  And everything in between, like humans.  So certain researchers have been investigating the origins of these differences in social character.

You got it:  Mom.

When rat babies are born, their mothers lick them in a mammalian bonding gesture like human cuddling and caressing.  Some go at it truly, madly, deeply.  Others, more indifferent, lick their offspring with varying degrees of enthusiasm.  As the babies get older, they start venturing away from Mom to seek adventures of their own.  Even good rat moms don’t hover, prevent them from taking risks, adjudicate their kids’ fights, or do their homework, so to speak.  But when the little rat does run into trouble — with a predator, a fall or a fight — they return for a good dose of licking.  The licking lowers their stress level, assures them someone’s there for them, and rebuilds the confidence they need to get back out and cope with reality.

Well-licked rat babies grow up pleasantly-socialized, curious, and fun to be around.  Oh and btw, they live longer.  Poorly-parented rats become high-strung, fearful, aggressive, and at worst, full-on violent.

I first heard of these experiments years ago at a lecture by Richard Tremblay, a research psychologist from the University of Montreal.  He studied the origin of aggression which, he argued, could be greatly reduced with affectionate parenting.

With a charming French accent and naughty pleasure, Tremblay often repeated the word “lick.”  As George Orwell’s book 1984 exploited so well, rats hold an especially dark, yucky place in our imaginations.  So, at Tremblay’s lecture, even super-open-minded Brown University folks were squirming with a lot of “eeuuu!”

Still, there it is:  nurture affects nature.  Or, as the biologists put it, epigenetic events strongly affect how your genes are expressed.  Your DNA is what makes you you.  But your Mom can make you way better.  (Actually, I already knew that.)

More recently, RadioLab produced a terrific interview with researchers Michael Meaney, from McGill, and Frances Champagne, from Columbia, who’d also researched the effects of good and bad rat parenting.  Their technique was to switch the rat babies of affectionate moms and indifferent ones.

Like most of us, rat moms parent much as they were parented.  So the ones who got a lot of affection, tend to give affection generously, thereby reproducing a bloodline of pleasant rats with affectionate DNA.  Similarly, aggressive DNA is passed on by indifferent rat moms.

Yes, humans can make rational choices about such things, but surely you know people who complain bitterly about how they were parented, and then turn to their own kids and neglect, constrict or criticize them in exactly the same ways.  Parenting styles are largely inherited.

The researchers found that when affectionate moms licked and cared for babies born of indifferent mothers, those babies became more trusting and social than would have been their genetically-determined path.  If DNA is genetic software, the epigenetic environment can alter the code.  The good-mom’s loving tongue licking the aggressive mom’s baby lets the genes “express” themselves, as the scientists say, in a river of neuronal bio-chemistry that produces pleasure, reassurance and calm.  The born-nervous baby calms down, fears less and trusts that she will be comforted if she falls down and goes boom.  The researchers’ switcheroo reprogrammed a baby’s aggressive DNA inheritance, allowing her to be a good parent herself some day.  (And vice versa.)

Assuming rats have something to teach us about ourselves, which I do, we have three take-aways.  First, moms need to know that affectionate nuzzling is far more likely to send their kids to Stanford than Einstein videos or toddler academic tutoring (which totally exists, if you didn’t know).  Second, that humans can change their behavior if they so choose.  Reluctant moms who are indisposed towards goofy baby-play need to get over it.  Seriously.  They need to suck it up and learn to lick their little rat.  Third, and perhaps most important, if a kid isn’t getting their cortisol level reduced by a generously-licking mom, the extended family or community absolutely must find someone to step in.  Otherwise aggression or other mental-health issues will follow.

And when that happens, once again, folks will point fingers and, that’s right, blame Mom.

So, on the occasion of May is Mental Health Month — and especially on Mother’s Day — let us heartily commend those profoundly affectionate moms, who don’t hover, but do console.  Because above all, we need a nation of well-licked rats.

Julia Steiny is a freelance columnist whose work also regularly appears at and She is the founding director of the Youth Restoration Project, a restorative-practices initiative, currently building a demonstration project in Central Falls, Rhode Island. She consults for schools and government initiatives, including regular work for The Providence Plan for whom she analyzes data.For more detail, see or contact her at or c/o GoLocalProv, 44 Weybosset Street.

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