The Fascinating Reason Your Kids Might Be Polar Opposites

When it comes to personality, my kids are opposites in almost every way. My son, four years older than my daughter, has always been outgoing with new people, noisy, obsessed with all things science, critical, inattentive, short-tempered, messy, easily bored, a homebody, and doesn’t give two shits what people think about him. He doesn’t care what the customary way of doing things is—he’d rather come up with his own way and instruction manuals can fuck all the way off. He is unmotivated by rewards, impressively stubborn, and will argue all day and night about something if you engage him.

My daughter is slower to warm up to people, more into arts and crafts, has the ability to focus for hours, loves getting out of the house no matter where we’re going, and is compliant almost to a fault. She worries what people think about her and cares a lot about “keeping the peace,” sometimes even to her own detriment. If she even thinks she’s in trouble, she immediately apologizes and tries to remedy the situation.

A few traits my kids do share, though, is that they are both loving and kind. Both are always up for a good snuggle session and both care deeply for the well-being of other humans, animals, and the earth in general. I love that they share these traits.

But because of those other big differences in their personalities, I find I have to parent each of my children very differently. Since rewards don’t motivate my son, he needs a more punitive style of parenting. He learns from negative consequences, as in, when he misbehaves, he loses screen time. But to say, “Behave, and you’ll earn screen time” just doesn’t work with him. The potential for a future reward somehow doesn’t click as motivator in his brain the way misbehaving and then losing a privilege for a week does. He needs to be able to experience the sudden loss of what he loves, feel the pain of that loss, and be able to recall that pain the next time he’s about to act up.

I have to be more gentle with my daughter. She is so compliant, so eager to please and afraid to offend, that my goal is actually the reverse of how I approach my son. With my son, I almost feel a need to take him down a few pegs. He can be arrogant with his assertiveness, too aggressive in his mission to prove himself right.

My daughter, on the other hand, exhibits the kind of need to please that I worry may one day put her at risk for being a victim of abuse. I need her to work on her assertiveness, to speak up when she doesn’t like how something is going, to defend herself when she knows she didn’t do anything wrong. I have seen her apologize just to keep the peace, even when she’s done nothing wrong, and I desperately do not want her to carry that habit into adolescence or adulthood.

So what I end up with in parenting these two little creatures who are so vastly different from each other, is a big ol’ mountain of guilt. Primarily I worry that my son thinks I favor my daughter—he’s even said it before, that I like her better. The truth is, I am amazed by my son. Yes, I want him to work on accommodating other people’s opinions and points of view, but I’m in awe of the clockwork nature of his brain and how quickly he can analyze and understand a situation or piece of machinery. I love that at 13, he still says, “I love you, Mommy.” The kid melts my heart every day.

And though it may be tempting to say my daughter is “easier to parent,” that also isn’t true. She’s only nine. What if I can’t shape her into assertiveness? What if she gets treated like a doormat in high school or gets into a bad situation with an asshole in college? My parenting of my daughter may be quieter than my parenting of my son, but it is no less fraught with fear and even sometimes frustration.

But how did two kids from the same gene pool and raised in the same environment end up so different in the first place? Psychologists have a theory called “non-shared environment” about how children raised in the same household can be so different. The label is a bit misleading because it’s referencing what is literally a shared environment, but the “non” on the front has to do with the experience of living in that same environment. The environment may be the same, but the experience very much isn’t.

Birth order has long been thought to influence personality, with the first child generally being more in control, more compliant, higher-achieving, and the second child more prone to be the “wild child.” That’s supposedly due to this non-shared environment. The first child is born into a situation where the parents have their entire attention devoted only to them, doting and obsessing over getting everything right. The stakes feel so high with that first child, and the child feels that and behaves accordingly.

The second child is born into a family of divided attention. They have an older sibling they must compete with. They may find they can’t compete in some ways and so intentionally choose a different path. They may act out as an alternative to competing, failing, and being perceived as “less than.” Parents are less rigid with their schedules, more relaxed about rules. And so the second child “becomes” more wild.

So, as the theory goes, though the same two children are born into the same environment, their experiences are not shared. Non-shared environment.

Except, more and more, psychologists are starting to wonder if the variation in sibling personalities is simply a difference in in-born personality. Birth order and non-shared environment may have less to do with personality and parenting style than the genes influencing the child’s personality. It used to be that, in terms of the success or failure of an adult child, it was assumed that parenting played a massive role, was almost the entire reason, in fact, for the success or failure of a child. Children’s behavior was said to “reflect on” the parents. We still do this, actually—how many times have you looked to the parent when their kid acted like an ass? We all do it.

It’s both discouraging and a relief to think about, but as the science progresses, we are beginning to see that, in the nature versus nurture debate, nature plays a far greater role than we ever realized. Where we used to think that siblings behaved differently because parents treated them differently, now we’re starting to see we may have interpreted this causal relationship in the wrong direction. It’s not the parenting that changes the kid’s personality. It’s the kid’s personality that influences how the parent treats the kid.

In other words, my son doesn’t misbehave because I parent him more harshly than my daughter. I parent him more harshly because his personality requires it.

Studies bear this out, but I was already confident my kids’ differences were not a result of birth order or a difference in how I treat them. They were incredibly different even as infants. Literally from day one in the hospital, their personalities were already starting to show. My son stayed up the entire first night, eyes wide, examining everything in the room, and my daughter snoozed peacefully, eager to adapt to ordinary circadian rhythms as quickly as possible. My son was colicky and had a hard time self-soothing, needed constant contact and affection, and my daughter would get annoyed if you tried to continue to hold her after she’d fallen asleep. She wanted to be in a quiet room by herself. We had to do cry-it-out with my son but not my daughter.

This isn’t to say that nurture plays no role. Of course it does. It’s critical for children to feel attached to their caregivers and to have all their physical and emotional needs met. But all those things do is allow for their true personalities to emerge. And that’s the part we may not ultimately have a whole lot of control over.