There are many contributing factors other than the attachment style that is developed as an infant that contribute to the overall deveolopment of a child. I think that a bigger contributing factor is the social environment that the child is raised in. If the relationships of the people around the infant are well-balanced and loving then the child will respond positively and emulate those later in life. One negative example is when a family undergoes a domestic disturbance such as a divorce. This drastic shift in the family dynamic can change attachment styles and negatively impact the development of the child.
