YAB a bit U. Yes, external influences will be there, but I do believe that a solid base level code of decency will provide a great advantage. I did do some rebellious stuff as a teen (drinking, taking cannabis, lying about where I was going etc) but there was an unconcious line drawn, as I loved and respected my parents a lot, and knew it would hurt me to upset them.
Having been educated by Jesuits, I have seen the "give me the boy until he is 7 and I'll show you the man" and I do believe there is a grain of truth in it. I am no psychologist. In fact, I'm a vet! With puppies, for example, there is a "critical period" for socialisation between about 7-16 weeks, when things become "normalised", and it is harder to change hardwired behaviour (but not impossible) outwith this period, so it is very important to get this part of the pup's life right. I know it is tenuous (and I am very guilty of trying to bring my children up the way I did my dogs! ) but I can't help wondering if there is a similar (but obviously more protracted) period for humans. Whether what a child experiences between the ages of say 1 and 7 becomes "normalised". That is not to say that it is set in stone, but it becomes the basis for normality- things like a stable, loving home, with no fear. To feel worthwhile and capable. To have the courage and confidence that comes from knowing you are loved and cared for. The idea that you have some kind of social and personal morality.
I have 3 children. they are all very different, and DH and I have often joked about how they will be as teens. DD1 (currently 7, and a stickler for rules and fairness) I think will be gobby (as she is now) and defiant (as she is now, when she perceives something as "unfair") , but ultimately I think will reluctantly toe the line, more or less, with much protest and flouncing.
DD2 (6) is a bit sneakier and more of an individual thinker. I imagine she will be a challenge. I think she will get away with whatever she can, and will eschew the arguing for simply doing what she wants (eg staying out all night) and accepting the consequences later. My guess is I will have to keep my wits about me to keep up with her. But I will never stop trying, and she will know I love her, deep down, even if she hates me.
DS (3) is a moody little git. I envision lots of strops, and a fair bit of defiance and swagger. I can see battles between him and DH. He is very very determined, and even at this age I find I have to take a harder line with him, as he is at great risk of being overindulged by his loving sisters and because he is the youngest and only boy.
Will it work out the way I think? Who knows! My dad always said that even in my more obnoxious days, and despite horribly unsuitable boyfriends/ drinking/ bad behaviour, he felt confident that he "knew" me and that I would come through it fine, based on my intrinsic personality and the values they instilled in me. I hope my children will be the same. One thing is for sure, I will never sit back and shrug my shoulders and say "nothing I can do".