Problems with decoupling self from others: An experimental approach to mentalizing about self and others in borderline personality disorder

The capacity for self-other distinction (SOD) refers to the ability to distinguish one’s own body, actions, and mental states from those of others. Although several theoretical and treatment approaches, such as mentalization-based treatment and transference-focused psychotherapy, suggest that impairments in the capacity for SOD may play an important role in explaining key features of patients with borderline personality disorder (BPD), little empirical research to date has directly focused on SOD in BPD. Furthermore, in recent years, novel insights into the neural and behavioral mechanisms involved in SOD have emerged from the fields of social cognitive neuroscience and experimental psychology. However, these insights have not yet been applied to the study of SOD in BPD. Building on these efforts, this doctoral research project aims to provide a better understanding of the nature of impairments in SOD impairment in BPD, which may have important implications for the treatment of this condition. Based on a review of existing neural and behavioral evidence on SOD in BPD, a conceptual framework for understanding SOD in BPD was developed. Furthermore, several experimental investigations of SOD in BPD were conducted in the context of this doctoral research project, both in non-clinical participants with elevated BPD features and in clinically diagnosed BPD patients. Specifically, we investigated embodied SOD in BPD using the self-other facial morphing task and the Enfacement Illusion task. Mental-state SOD in BPD was studied using the transparency estimation task, referring to the ability to correctly estimate the extent to which one’s own mental states are observable to others. Findings of this doctoral project suggest that individuals with BPD have problems with SOD in terms of difficulty flexibly shifting between and co-representing self-other representations, and that they exhibit difficulties in embodied SOD as underpinned by multisensory integration. These impairments have important implications for BPD patients’ self- and interpersonal functioning, although more research on SOD in BPD is needed.