I've been thinking a lot recently about the concept of differentiation. Differentiation is an outgrowth of normal psychological and emotional development. It gradually develops throughout childhood and adolescence. If all goes well, the process culminates in an adult with a well defined sense of self and the capacity for intimate relationships with others. Different people achieve varying levels of differentiation. The Bowen Center (http://www.thebowncenter.org/) explains the difference between a well-differentiated individual and someone who is poorly differentiated.
A person with a poorly differentiated self needs frequent approval and validation from others in order to feel good about himself and to maintain an inner sense of stability. Without it, a poorly differentiated person feels unworthy, insignificant, and even empty. Because he needs others' approval and validation in order to feel stable, a poorly differentiated person tries to control the people in his life, either overtly or covertly.
These are the people you know with "control issues." They are the ones who cannot tolerate disagreement from others. They are easily overwhelmed by their emotions and look to external sources (such as alcohol, sex, eating, shopping, etc.) for comfort when they are distressed. They are those who go along with what "everyone else" says and does and who are not able to stand up for themselves or to speak their minds. They often have problems in interpersonal relationships because they expect others to meet their emotional needs and feel angry or rejected when they don't.
A well-differentiated person recognizes the importance of interpersonal relationships and acknowledges their influence on his thoughts, feelings, and behaviors. He has, however, a clear set of values and goals that guide his decisions. He experiences strong emotions but is not controlled by them. He is comfortable accepting or rejecting another's viewpoint based on its merits, not on his desire to influence the other's opinion of him. He is able to comfort himself when he is upset and copes with negative emotions in ways that are not harmful to himself nor to others. He is comfortable with himself and so has no anxiety about revealing his true self to other people in the context of an intimate relationship.
So what determines an individual's level of differentiation? This is one instance where the cliche that all adult problems have their origins in childhood actually applies. The level of differentiation you achieve depends upon the degree to which your family of origin meets your emotional and psychological needs throughout your childhood, thereby endowing you with the inner resources needed for you to grow and develop as an individual. Dr. Robert Noone describes this as "the degree to which the emotional unit of the family has been able to allow that individual to grow toward emotional maturity."
The theory is that individuals achieve about the same level of differentiation as their parents and that by the time an individual reaches adulthood, his or her level of differentiation is pretty well established. It is very difficult - but NOT impossible - to achieve higher levels of differentiation after a person reaches adulthood.
There is actually a scale that measures an individual's level of differentiation. Here's the link, if you're interested: http://www.personal.psu.edu/eas14/The%20Differentiation%20of%20Self%20Inventory,%20Development%20and%20initial%20validation.pdf
It's a PDF file; the scale is on the last page (pg. 12 of 12). I haven't taken it yet, but I'll share my score as soon as I do.