some factors that may affect the independent and dependent variables of a child and his or her relationship with her mother can be:
-environment: maybe the child is not happy? poverty? dangers of environment?
-degree of care of mother/father: mother may be too clingy...maybe even too caring, inhibiting the future harder for that child, possibly. Or the father figure could be abuse, or maybe not even there at all as to give the child a model of a father figure
I think that the environmental variable is one that is very likely and has definitely been seen to effect relationships, especially when someone is living in an extreme environment as they are developing and doing a lot of learning, as a young child does.