Genes + environment = personality. Personality + situation = behaviour
I don't think this accounts for everything.
You have some control over what parts of you personality are expressed. The whole nature vs demeanor thing.
Personality + situation = behaviour
Also, you have a choice in how you behave that is independent of your personality. We are not at the whim of our urges. We can choose to behave in a way that goes against what comes naturally, or go against how we are compelled to behave.
Of course you could just push it back to going against the compulsion is the behavior you have no control over. But it is counter intuitive to me.
It certainly
seems like I am choosing the behavior I exhibit.
Of course, that doesn't prove that I am. But I think its going to be hard to convince me that I'm not.