The Genetics of Parenting

Most parents live in fear that their decisions will permanently mess up their kids. It turns out, according to new research, that kids can also mess up their moms’ and dads’ parenting decisions.

It’s obvious, if seldom said out loud, that some kids are more difficult than others—and that it’s a lot harder to be warm and patient with a child when he’s being difficult. A new paper draws on a rich history of behavioral-genetics research on this issue and also makes a novel contribution, pinpointing specific Big Five personality traits in children that may play a role in connecting their genetics to the parenting they receive.

The idea that good parenting is partly a function of having easy-to-deal-with kids raises some uncomfortable questions for those of us who like to be judgmental of the other dads at the park, of course. It also makes it difficult to measure the long-term consequences of parenting, as so many studies have tried to do, because any measure of parenting will almost certainly measure the child’s traits indirectly as well. And, of course, these results provide important background information to those who want to help parents do a better job. It may be that to improve a home environment, one must consider the unique proclivities not only of the parents but also of the children.

The basic insight of behavioral genetics is simply that twins and adoptive siblings provide a window into the power of genes: If identical twins tend to be more similar than fraternal twins even when they’re raised in the same home, for example, this is strong evidence that genes are at work. With data collected from these types of siblings, statistical models can even estimate the degree to which the variations among them are genetic and environmental in origin, with the “environmental” bin divided into parts of the environment that siblings do and don’t share. (The answer for the typical human trait: half genes, with the other half overwhelmingly accounted for by the unshared environment.)

Numerous studies over the years have used these methods in a somewhat counterintuitive way, estimating the degree to which the parenting a child receives is dependent on the child’s own genes—which can happen if kids provoke certain reactions from their parents, or even deliberately mold the interactions they have with their caregivers. As the new study recounts,

Avinun and Knafo (2014) conducted a meta-analysis of child genetic and environmental influences on parenting in child-based twin designs. They found that 23% of the variance in parenting behavior was attributable to child genetic effects, 43% to shared environmental effects, and 34% to nonshared environmental effects. Another meta-analysis of genetically informative studies of parenting estimated that 26% of the variance in parental warmth was attributable to child genetic influences, 39% to shared environmental influences, and the remaining 35% of the variance attributable to the nonshared environment (Klahr & Burt, 2014). Parental negativity was slightly more strongly influenced by child genetic influences (40%) compared to the shared environment (27%), with the remaining 33% of the variance attributable to the nonshared environment.

Interestingly, the “shared environment” is a lot stronger in this line of research than it is in most other areas of behavioral genetics, suggesting that parents do bring a consistent approach to all of their kids to some extent—though, of course, this might be a result of the parents’ own genes. Unfortunately, the authors don’t discuss parental genetics in much depth, but the Klahr and Burt research review they cite concludes there are also “significant effects of parental genetic makeup on parental behavior.” So, when researchers rate interactions between parents and their kids and think they’re measuring “parenting quality,” one could argue that they’re actually, to some degree, just measuring the natural interplay between two hardwired personality types.

Anyhow, the new study includes more than 1,400 twin sets; the twins’ parents answered a questionnaire about their interactions with each child (“TWIN1 does things that really bother me,” and so on), and researchers measured the kids’ personalities using a child version of the Big Five Inventory. Like previous work, the study finds that children’s genes affect the parenting they receive, with identical twins being parented much more similarly than fraternal twins are. Child genes accounted for 45% of the variance in parental stress and 27% of the variance in parental warmth.

What’s interesting and new, though, is an additional analysis in which the researchers tied the measured effect of kids’ genes to their personalities. They found a significant link “between child genetic influences on warmth and child agreeableness and conscientiousness,” and also a link “between child genetic contributions to stress and child agreeableness.”

“Want to be a good parent?” the paper seems to ask. “It helps if you start with conscientious and agreeable kids.”

One can only be so confident in any study that relies on self-report questionnaires and psychological tests, of course. And these “classic” twin studies will likely fade as more modern and complicated genetic research—the kind that identifies specific genes rather than overall genetic contributions—takes over.

Some especially tantalizing new research suggests that parents’ genes can affect kids’ outcomes even if the kids don’t inherit those genes, presumably because the genes help the parent provide a better environment.

But however future studies shake out, you have to admit that, by the luck of the draw, some parents have it a lot easier than others.

Robert VerBruggen is a deputy managing editor of National Review.