There is a fantastic article by Dr. Craig Childress about the nature of the splitting dynamic that is characteristic of both borderline and narcissism. The article elaborates the equivalence of both at the attachment level and explains the defense mechanism splitting and gives neurological explanations as well. The article then goes into detail how splitting plays a key role in parental alienation.

You will learn how a person with borderline and/or narcissistic traits is neurologically unable to simultaneously experience both positive and negative perceptions of a person. When a breakup occurs, the ex husband for example becomes the bad/evil husband. In the black-and-white polarized brain pathways the “bad husband” MUST also become the “bad father” or in the case of a step father, you become the “bad step father”.

Since their brain fundamentally cannot experience ambiguity, the ex or ex spouse must also become a bad father, or bad step father. All memories held by the borderline person of the positive relationship the targeted parent may have had with the children are lost to relevance. The ex spouse has now become a bad parent, and the ex-husband must become a bad father or bad step father, and there is a “complete incapacity for emotional linkage” to any prior experiences of the targeted parent as a good spouse or good parent. These memories have “no emotional relevance.”

The article explains how the splitting defense mechanism realistically elevates the risk of false allegations of abuse directed towards the ex or ex spouse. It is described how the dynamic also significantly increases the risk of emotional child abuse as the borderline and narcissistic persons manipulate childs against the ex or ex spouse and how it comes to a role-reversal relationship in which the child is being used to meet the emotional and psychological needs of the borderline or narcissistic parent.

Rather than telling the child directly what to do or think, as does the behaviorally controlling parent, the psychologically controlling parent uses indirect hints and responds with guilt induction or withdrawal of love if the child refuses to comply. In short, an intrusive parent strives to manipulate the child’s thoughts and feelings in such a way that the child’s psyche will conform to the parent’s wishes.

Furthermore, persons with borderline personality traits may have been emotionally abused themselves (often by their mothers) and so have a pre-potentiated schema of fearfulness in which they see abuse where none exists (the term “borderline” refers to being on the “border” of neurosis and psychosis). Thus, they’re disposed to misinterpret events during or after the relationship and to construct delusional beliefs which can harm children and their mental health but also the ex-spouses as it often leads to the mentioned false allegations, distorted views and severe trust issues.

Typical core beliefs of a person with borderline traits are that other people are malevolent, cannot be trusted, and will abandon or punish you, especially when you become intimate with them. These issues but also attachment issues in general, are often the consequence of having growing up with a personality-disordered parent themselves , for example a narcissistic mother. When a child is raised with controlling, emotionally unavailable or unpredictable parenting, or emotional abusive parenting, the consequences of this upbringing are attachment issues.

Narcissistic mothers are for example controlling, blaming, self-absorbed, intolerant of others’ views, unaware of their children’s needs and unaware of the effects of their behavior on their children, and require that the children see them as the parents wish to be seen. They may also demand certain behavior from their children because they see the children as extensions of themselves, and need the children to represent them in the world in ways that meet the parents’ emotional needs.

Children raised by narcissistic parents come to believe that all other people are narcissistic to some extent, that you can not trust people. As a result, they orient themselves around the other person in their relationships, lose a clear sense of themselves, and cannot express themselves easily nor participate fully or independently in their lives. That’s the consequence of having been controlled the entire life.

They can only see things in extremes due to their dichotomous thinking. At first the partner will be seen as all-good, ideal, and wonderful or later as all-bad, entirely devalued, and demonized. They alternate between those two states, and that is called splitting. People are either idealized as the all-wonderful source of nurture and narcissistic supply, or they are entirely demonized as being “abusive” and as “deserving” to be punished for their inadequacy.  Splitting involves black-or-white extremes of polarized thinking and perception.

But at some point they devalue and demonize the partner (and now ex or ex spouse permanently). And that’s when their distorted perceptions will likely lead to false accusations, smear campaigns and sadly also to manipulation of children and parental allination.

You can read the mentioned article here.