Really good questions. I'd love to read some research on this association between attachment and unmet/met needs. Since perfection in parenting is an illusion, I do wonder if the intensity of the therapeutic relationship has the potential to pull previously unrecognized unmet needs to the surface, and so manifest as transference. I'm sure that temperment also plays a role, and what would elicit transference in one person, maybe wouldn't be of sufficient intensity for another.

But I also think there isn't enough attention paid to mixed parenting states, even in the face of tremendous abuse. Children, in particular, are often very capable of compartmentalizing their experiences. When abuse happens at very young ages--like 6 months to 3 years--it can prevent children from developing the capacity to merge feeling states and perceptions, resulting in personality disorders like BPD. But children who get past those ages before significant abuse happens have usually developed the flexibility to be able to merge feeling states or not, depending upon circumstances. So the parent who abuses, can also be accepted as the same parent who nurtures.

I know for me, my parents were abusive. There was also alcoholism during a large number of years of childhood. But the difference was that while there wasn't enough nurturing during the earliest years, there probably wasn't abuse (instances of inappropriately severe punishments, but not a sustained pattern of abuse). So I was able to develop that flexibility of perception. My mother, however, was cold and angry when she wasn't abusive. My father was nurturing and soft-spoken when he wasn't abusive. So my child's brain was able to separate my father's nurturing presence from his abusive presence and allow them to co-exist. I could benefit from his nurturing, despite the abuse.

So while there were many unmet needs brought to therapy, I also brought a "hopeful" transference--the capacity to trust and attach and not be beset with fears of abandonment. My transference, despite occasional fears, largely derived from the healthier parts of myself. I'm sure it's why I preferred a male T. I think the needs that can be healed through transference are largely those not met in childhood; but the capacity to attach probably stems from those needs that were met in childhood, whether such met needs are conscious or not. Those who have tremendous difficulties with capacity for attachment, and who experience the push/pull issues of trust and abandonment, developmentally, probably have unmet needs from an earlier age and little nurturing--or less ability to recognize what nurturing there may have been--to bring to the therapy relationship.