I think this explanation of cause and effect, the attachment gained from primary caregiver being the IV, and the well being in life being the DV, I think this neglects to acknowledge individual behaviors of a child. Some children may be naturally shy, or naturally outgoing, regardless of initial relationships gained between themselves and parents.
Also, it doesn't acknowledge a genetic predisposition towards some conditions. Some children could suffer from autism, a disease that doesnt allow the child to make good connections with people, even though he may have been given alot of attention and care as a child.
