AffectionateTouch Is Better For Brain Growth


If you’ve seen the headlines, you might have gotten the wrong idea – that new brain research suggests “two parents are better than one,” or that “kids raised by both parents” experience “better brain development.”

Provocative, right? But rather misleading. The study in question focused on mice, and what researchers actually discovered is this:

If you provide a mouse mother with an adult helper (of either sex), her offspring get licked and groomed a lot more, and this stimulates growth in specific parts of the brain.

In other words, two parents are not necessarily better for brain development–but lots of physical affection might be.

That’s a cool result, and it’s a result that’s consistent with lots of other research on rodents. When rats and mice get “extra” touch during infancy, they experience enhanced brain growth. This usually translates into better learning abilities (at least for spatial tasks) and an increased tendency to explore. Studies also show that extra licking and grooming makes pups less reactive to stress.

So extra lovin’ during infancy can produce lasting developmental effects in rodents, and we’ve reason to think that the same may be true of us. As I note here, a recent study of humans suggests that “at risk” babies who receive more affectionate caresses are less likely to develop stress disorders.

Moreover, what’s really fascinating is the idea of transmitting these effects to the next generation. Previous research suggests that certain environmental triggers can “methylate” a rodent’s genes, determining whether or not specific segments of DNA get “turned on” or “turned off.” In this way, the environment can alter the way genes get expressed, and these changes can get passed onto offspring.

It’s been studied for bad stuff – like early life stress. What about the good stuff, like affectionate touch?

In the new study, Gloria Mak and her colleagues tested the idea. After establishing that male mice raised by two parents experienced more growth in a part of the brain called the dentate gyrus, the researchers mated these males to the daughters of “single” mothers. The resulting offspring were raised by just one parent, so they got less licking and grooming. But the boys nevertheless showed enhanced growth in the dentate gyrus. They were, it seems, benefiting from the extra licking and grooming their fathers had received a generation before! The researchers observed a similar phenomenon among females, though in that case the brain region of interest was the corpus callosum.

Which brings up another point. In this interesting study of mouse parenting, males and females didn’t receive the same benefits. Compared to males raised by single mothers, males from two-parent families enjoyed a boost in growth to the dentate gyrus. But for females, parenting had no effect on the dentate gyrus. Instead, it influenced growth in the corpus callosum.

Why the sex differences? The researchers aren’t sure. But they remind us that we have to be careful when making generalizations. If the effects of “extra” parents differ within a species, it seems likely they differ between species as well.


What does all this mean for humans?

This research does not tell us that human children living with two parents will have “better brain growth” than will kids in single-parent homes. Yes, kids from dual-parent families are often better off – for one thing, they usually have higher socioeconomic status. And it’s not hard to imagine a scenario in which some children of two-parent households – because they more affluent and less stressed – enjoy developmental benefits. But that’s not what this mouse study is about. It’s really about the benefits of early, affectionate touch, and I think it offers a message of interest to everyone.

We can’t assume human babies respond to snuggles in the same way that rat pups respond to licking and grooming, but the power of touch is very ancient. It evolved long before the existence of humans, and modern research suggests we’ve inherited a need for touch. Might “extra” parenting – affectionate touch from mothers, fathers, grandparents, siblings, teachers, nannies – give our kids an advantage? It’s an idea worth testing in everyday life, even if there are no randomized, controlled experiments to guide the way.


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