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When my oldest son was a toddler, he never stopped moving. He crawled early and walked early, then quickly got around to jumping off walls and turning somersaults. Maybe he would be an athlete, I thought.

At the playground, Nate watched other children closely, mimicking and playing well with them, never hitting them or taking their toys. Maybe he would be really outgoing, I thought, adept at navigating social interactions.

When he got frustrated, Nate threw wild tantrums, dissolving onto the floor in sobs several times a day. Probably a phase, I thought.

My son is now 5, and he’s a creative, emotional introvert who’s entirely uninterested in sports but loves to raid the recycling bin for found objects to use in the wild sculptures he builds with tape and glue and staples. I did a terrible job interpreting his toddler personality, and the reason, I believe, is because I couldn’t tell what was toddler and what was his personality. Most toddlers are physically active, throw tantrums and make observations of other children. But understanding the degrees of difference within those normal toddler behaviors was too sophisticated for this first-time mom.

That’s why it’s been so fun to size up my second child now that he’s a toddler asserting a will of his own. At 17 months, Harvey is extraordinarily friendly in a way that Nate never was, enthusiastically greeting strangers on the street, grinning and flirting with them for as long as they will let him. I have to watch him closely on the playground because it’s not unusual for him to pinch other kids and pull their hair. He was much slower to crawl and walk than Nate was, but that’s because he’s more physically precise. He has an eye for detail and a great throwing arm; I now have him pegged as the outgoing, easygoing athlete to his brother’s temperamental artist.

Kids change, of course, and my predictions today could end up being as wrongheaded as my earlier ones were. And yet, while I can’t confidently predict their career paths, I am more confident in reading my children’s basic personality traits because I recognize them so well.

My husband, Aaron, is the most extroverted person I know. He can talk to anyone, makes friends everywhere he goes and is usually the last one to leave a party. Being around people charges and energizes him. We spent our honeymoon traveling around the Yucatan Peninsula, exploring ruins and beaches, just the two of us. Aaron’s a very romantic person, and he was thrilled to get married and take this trip together. And yet, on the second week of our honeymoon, he told me he was “lonesome” because we were spending so little time with other people.

That’s Harvey all over. Being around new people lights Harvey up and can snap him out of a bad mood. Social gatherings fuel him, and unlike many kids, he doesn’t get overtired and crash.

I’m the opposite, a classic introvert who enjoys spending time with friends but needs time alone to recharge. I relate so strongly to Nate when he comes home from school worn out and sits outside by himself or shuts himself in his room to unwind. It’s sweet for me to see myself in him, but it makes me ache for him, too, because I know how it feels to be the kid who’s shy, quiet and inward. He just started kindergarten, and it’s hard for him to be in a new school with a big class of kids he doesn’t know.

My hope is that by relating to how he experiences the world, I can help him through the tough parts. And I can tell him from my own experience that whatever life he has as an adult, the ability to be alone, self-reliant and reflective will be something he treasures in himself.