Building on Bowlby’s early assertions that internal working models of self and others form key features of the attachment  system, supported by research which has indicated that these views are related to infant attachment, Bartholomew (originally in 1990) proposed a new attachment classification system of four types. This involved adding a second type of avoidance to the existing three classification. This additional type differentialted between fearful avoidant and dismissing avoidant and was based on a similar category from the Adult Attachment Interview (George, Kaplan & Main, 1985). This was tested against 15 dimensionsal interview which was found to confirm the underlying structure. Their four category self-report item called the Relationship Questionairre was later revised and scored on a seven item Likert scale.

Subjects classifications were: