Really interesting question.
For my part, I also think people have the twice sides inside, some of us increase the right side and some other the bad one. this is done by the fact we can live in our lives and of course, by the basis we had during the education time.But some of people also have a kind of little "failed part" and sometime from this, it results a really big changing, in the bad side.
we are all fragile. Events, family problem, money problem can increase a kind of desepering feeling and pushing people through few things they wouldn't do if they had found a solution, a rational one!
It was just my feeling about the question asking in the article and in substance, coz i'm unableto enter in the subject with the perfect words in English. Just wanted to share!