Although borderline personality is characterized by a variety of interpersonal antecedents and consequences, interpersonal theory has yet to develop an adequate model of the disorder. It was hypothesized that considerations of non-interpersonal features that influence interpersonal behavior can inform the description of the interpersonal process associated with borderline personality. Specifically, it was proposed that borderline personality is not adequately conceptualized as characterized by rigid and extreme traits. Instead identity diffusion, or under-developed personality organization, characterizes the disorder, as do notable problems with perception and behavioral impulsivity. Three samples of dyads interacting in a collaborative task were compared using structural equation models of their traits and situational behavior from the perspectives of multiple raters. Two samples included dyads without a borderline interactant and one dyad had one person with and another without borderline personality features. It was hypothesized that dyads including borderline participants would manifest behavior that deviates from normative interpersonal processes.

Results were consistent with hypotheses in suggesting that dyads without an individual who has borderline characteristics demonstrate very similar interpersonal patterns, whereas dyads with a borderline interactant deviate from normative interpersonal process. Specifically, borderline individuals appear to be hyper-perceptive of others’ efforts to control (dominate or submit to) them. With regard to affiliation (warmth vs. coldness), borderline individuals appear to have very different perceptions of their own interpersonal style than do individuals who know them, and unlike nonborderline individuals, these styles exert minimal influence on their behavior in interpersonal situations. These results suggest practical implications that vary across interpersonal dimensions. Data imply that clinicians should take seriously suggestions by borderline patients that they feel controlled. With regard to affiliation, data are consistent with the theory of identity diffusion in suggesting that borderline personality features are associated with a lack of stable interpersonal traits that influence behavior across situations, and the development of such a style is an important therapeutic target.