I find psychology to be pretty interesting. I don't buy into everything I read, but at the very least, it's fun to hear theories. I recently finished the book "The New Birth Order Book" (Kevin Leman). It's all about how your birth order (first born, middle, baby, only child, ect..) effects your personality.
I was sold on the book when it described Joel and his second brother perfectly, lol. It's like he wrote it about those two! Anyways, I see alot of Sam in what he describes as the first born (although I'm sure I could find the other traits in him as well). I don't have time to look it up in the book, so I just googled it (this is several chapters in a couple sentences):
Sam's already our little perfectionist. He's the kid that gets upset when the other kids don't follow the rules...Probably about a year or so ago I told him that you were "supposed" to color inside the lines and he has been serious about it ever since. Anyways, thought I'd recommend this book. It's fun to compare people you know to their birth orders and see how they match up. Oh, and I'm not sure what my birth order actually is, but I think I go towards the firstborn the most.