OBJECTIVE: Deficits in mentalization ability have been theorized to underlie borderline personality disorder (BPD) and have led to mentalization-based treatments. Yet there has been little empirical investigation into whether mentalization deficits do differentiate the BPD population from healthy controls, and the specific nature of these differences.
METHOD: Five pre-existing Theory of Mind (ToM) tasks that assessed simple to complex mentalization capacity in both the affective and cognitive domains were administered to the same groups of age and gender matched patients with BPD and controls. Self-report measures assessed cognitive and affective empathy and childhood trauma and abuse.
RESULTS: The BPD group did not differ significantly from the healthy control group on basic cognitive false-belief picture-sequencing tasks, or on overall accuracy when discriminating mental states from viewing images of eyes, and attributing emotions based on social events. They were, however, significantly less accurate in identifying positive mental states on the Reading the Mind in the Eyes (RME) task and showed significantly more mentalization errors on affective and cognitive understanding of faux pas (faux pas total score p<.01) and on a Joke Appreciation task (p=.01), that required integration of multiple perspectives. They also self-reported less empathic perspective taking (p<.01). Observation of patterns of performance hinted at specific underlying biases (e.g. a default tendency to use superficial black-and-white attributions to others, such as, "he is mean", when explaining behavior). It was also found that as childhood experiences of punishment increased, adulthood mentalization ability decreased on all affective ToM tasks and on the cognitive and affective components of understanding faux pas.
CONCLUSIONS: The BPD group was as capable as controls in undertaking simple mentalization. However, deficits in mentalization capacity became evident when mentalization tasks became more complex and required the integration of multiple perspectives. Increasing childhood experiences of punishment were related to decreasing mentalization ability in adulthood. Findings support the use of treatments to improve mentalization skills in BPD, however, further research is needed to better specify the nature of underlying mentalizing biases in this population.