Nature vs Nurture

When a child is born, do they come out with a brain already printed upon with their personalities? Are their characteristics pre-determined?

I wonder.

I always thought some of the nastier traits were learned. The ability to tap dance on another persons nerves for example. I understand that the response to the persons reactions is learned, but the drive to harass, the desire to reach out and torment another human as a way to occupy and enjoy yourself, that I always understood was inate. You are born with a mean gene that you can act on, or not. But you learn the ways to maximize the other persons discomfort.

Come to find out, a certain level of obnoxious-ness comes from within. And oddly, some children appear to have the natural ability to get right in there. Things I was positive had to be learned, may not! My world order is all smashed up!

How does one child know, KNOW, that to copy her sister, will drive her crazy. To repeat word for word, inflection for inflection, what the other has said, will allow the first child the opportunity to watch the second child blow up her own head. It is something I always thought was passed down through the generations on school playgrounds wherein the mean kids huddled together discussing the best torments and filling in the newbies. Or learned by watching bad tv shows. Or reading about it. Or hearing their evil cousins do it. Thousand of years worth of one sibling repeating what the other has said, thousands of years of the other saying 'stop copying me', thousands of years of the first child refusing to quit, and thousands of years of parents yelling out, "STOP COPYING YOUR SISTER".

I am coming to realize that for some, seeing a behavior is not necessary. It is inherent. The question, ''where did she learn to do that?" has no answer. She didn't learn it. She just knows. And since I have contributed to the genetics of one of my children, and I know what she has been exposed to, I can officially say I haved resolved the issue that has tangled through the brains of some of the most brilliant minds in history.
Nature vs Nurture solved.