From my little experience working with kids, (I taught swimming lessons for a couple years, and I volunteer at a preschool) I've been surprised to learn how very different they can be behaviorally speaking at such early ages. I think this has a lot to do with parenting, which is mentioned in our book on page 388. I also think that the style of parenting kids grow up with has long-term effects on development.
A parenting phenomenon that has been highly discussed recently is "helicopter parenting." I would classify a helicopter parent under the style the textbook calls an "Authoritarian." An authoritarian is strict, offering little freedom and much punishment. Helicopter parents are involved with every aspect of a child's life. Many interpretations of the term appear as comic strips with an apathetic looking kid in the middle of two hovering parents, one whispering an answer to the test they're currently taking and the other trying to wrap the kid in bubble wrap.
The term reminded me very much of many of my friends' parents in high school, in particular my friend B's mom. B's mom always decided what classes B would sign up for. She wouldn't allow her to take art because there were more important classes that would be "more beneficial to B later on in life." When I first started to hang out with B she admitted to being constantly stressed out, she told me how on holidays she would always get drunk in her bathroom because she felt like she didn't belong with her family and they didn't think she was good enough. This really freaked me out and I suggested she tell her mom how she felt about how much control she had over B. B's mom didn't like this at all and eventually stopped allowing B to come over to my house. She said I was a bad influence on her because my parents were too liberal and they were divorced so I was "troubled." As stated in our textbook the effects of divorce on children are variable and "better-designed studies show that the substantial majority of children survive their parents' divorce without long-term emotional damage." My parents' divorce came as a relief to me because I knew the constant fighting would be over. B's parents condemn divorce and yet have separate bedrooms and fight often. So then in 2008 came Bs transition and mine into college. While my parents had been lenient with me (or authoritative) I was reluctant to disobey them and their suggested limits because I was generally happy with life. When B got to college it was as if you let her out of a cage, once overwhelmed with structure and limitations B was now free to do as she pleased. She drank heavily and her grades suffered. So was the cause of this her helicopter mom? Or had she simply been wired that way..with little self-control, and thus her mom had no other choice but to constantly dictate her every action?
http://www.time.com/time/magazine/article/0,9171,1940697-1,00.html <---good article on helicopter parenting