If we consider that secure attachment and good outcomes later in life are both dependent varriables caused by the same independent varriable, then I believe the most obvious IV would be the home enviornment of the child.
If the child is in a stable home environment (either good or bad), they are likely to act in a similarly consistent manner, ruling out a disorgainized attachment. If they are in both a stable and good/loving enviornment it is probably more likely that they will display a secure attachment and have the family support and capabilities to succeed later in life.
I completely agree that the home environment has a significant impact on the child, even more than school itself because children tend to mimic their parents any way they can(who else are they going to learn from?) If a child is raised properly with nurturing parents than chances are, the personality and temperament of the child will return positive. This child will view the world with optimism and trust and since a t a young age his parents were his "world" later in life people translate this "world" as expectations for the outside world. On the other hand, if a child grew up in a household where the parents were always fighting and there was a lack of trust between these two people. this baby will grow up being cautious and wary of the world. He may not stay in a relationship for long or there even might be trust issues with this child because he grew up with it.
