Comparing siblings can be more harmful than you thought

As a parent, it's hard not to compare your kids to each other, what with everything you know about their feeding habits, developmental milestones and sleep schedules. I started comparing my children the moment I found out I was pregnant the second time. From first trimester morning sickness to a drug-free vaginal birth, everything about my second pregnancy was different from my first. Even afterward, I kept comparing Isaac and Gillian.

Some of the differences are stark: He's always been the better sleeper and more easygoing; she's a terrible sleeper with a spirited disposition. My husband and I try not to talk about these differences in front of the kids, but since they are now both in school, it's actually the two kids who are fiercely competitive with each other. And while we try hard to keep sweeping gender generalizations out of our conversations, Gillian is the better reader and Isaac is better at math. For example, at five years old, Gillian is already reading, whereas Isaac struggled until first grade. When it comes to math, Gillian is on track developmentally, but Isaac was so much further ahead at the same age.

I'd like to think their unique natures are as individual as their DNA, but emerging research from Brigham Young University suggests that our subtle comparisons may have had a role in how our children's personalities developed.

Recently published in the Journal of Family Psychology, the study focuses on the academic achievements of 388 teenage first- and second-born siblings in 17 school districts in the U.S. They interviewed the their parents to learn what they had to say about how capable their children were.

Lead author Alex Jensen says that parents often compare the elder sibling to the second, in the belief that the first-born is smarter. However, research shows that, on average, their academic achievements were similar. "The first-born likely learned to read first, to write first, and that places the thought in the parent's mind that they are more capable, but when the siblings are teenagers it leads to the siblings becoming more different. Ultimately, the sibling who is seen as less smart will tend to do worse in comparison to their sibling," Jensen says.

Researchers found that the teenagers' future report card grades were influenced by their parents' beliefs as to which child was smarter, even though these parental beliefs weren't based on past grades. The child considered to be smarter performed better than the one parents believed was less capable. The grade point average difference was small—only 0.21—but Jensen points out that over time those small effects add up.

An exception to these findings occurs when the sibling pair is an older brother and younger sister, like it is in my house. "Parents also tend to think their daughters are more academically competent than their sons, and, at least in terms of grades, that seems to be true," says Jensen.

With year-end report cards to be issued this week, I'll definitely have Jensen's research in the back of my mind. I can't promise that I won't compare my kids, but I'll be aware of how I talk about their grades in front of them. And, rather than pointing out when one child did better than the other, I'll celebrate every single accomplishment.

Follow along as Jennifer Pinarski shares her experiences about giving up her big-city job and lifestyle to live in rural Ontario with her husband while staying home to raise their two young children.

 @JenPinarski.