Baby development

Nurture over nature

Can your smiling face change your baby?

By John Hoffman
Nurture over nature

If there’s one thing I’ve learned about parenting, it’s that some kids are harder to parent than others. With these kids, the standard strategies don’t seem to work as well. And parents don’t always get the immediate feedback that their efforts are helping, whether it’s trying to comfort a high-strung baby, keep tabs on a get-into-everything toddler or help an “act first, think later” five-year-old. So it’s harder to know if you’re doing the right things.

Sometimes we just have to go on faith, telling ourselves that our efforts haven’t been wasted. Have you ever felt that way? Well, here’s a study that shows your faith may not be misplaced.

Researchers with the Center for Developmental Science at the University of North Carolina at Chapel Hill are following a group of babies, some of whom have low vagal tone — a reflex in which a nerve (called the vagus nerve) acts as a sort of brake on the heart. In stressful situations, that brake is removed so the heart can beat faster to help us deal with the threat. When the stress or threat is over, the brake goes back on, the heartbeat decreases, and we can calm down. In people with a certain version of a certain gene (let’s call it the risk gene), that mechanism doesn’t work as well, so they have a harder time dealing with stress. People with low vagal tone are more prone to poor emotional control, attention problems, aggression, substance abuse and other risky behaviours. This vulnerability is not obvious in infancy, but this research has shown that responsive parenting can lessen its effect.

Scientists can wire babies up to measure vagal tone. In this study, they assessed it while subjecting the baby to a mildly stressful situation (being ignored by mom). At age three months, the kids with the risk gene all displayed lower vagal tone than babies without the risk gene, regardless of the parenting they got. But at 12 months, babies with the risk gene whose mothers were responsive and sensitive had vagal tone similar to those without the risk gene. In other words, responsive parenting had a biological effect that cancelled the effect of the gene, a gene that, of course, they didn’t even know their child had.
Keep in mind that these sensitive and responsive mothers were not supermoms. They were average moms who simply paid attention, responded to and interacted positively with their babies in typical ways. However, some of the other mothers were more detached. They didn’t show as much of that animated motherly interest, such as smiling back when their babies smiled at them or showing interest in a toy that the baby was excited about.

What does this have to do with you, who will likely never know whether your child has low vagal tone or some similar genetic vulnerability? It means that your inclination to tune in to your kids, read their cues and respond to their needs is bang on and may have effects that go even deeper than you imagined. So if your baby cries, you go to her and try to figure out what’s wrong and comfort her. If she shows interest in a picture on the wall, you take her over for a closer look. If you sing and she lights up, you keep singing.

Sometimes you’ll see that your efforts are working, and other times you won’t be so sure. But this study suggests that in those uncertain moments, you’re probably doing more good than you know. So keep at it.

This article was originally published on May 11, 2009

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