The present study investigated transparency estimation, that is, the ability to estimate how observable one's emotions are, in patients diagnosed with borderline personality disorder (BPD) (n = 35) and healthy controls (HCs; n = 35). Participants watched emotionally evocative video clips and estimated the transparency of their own emotional experience while watching the clip. Facial expression coding software (FaceReader) quantified their objective transparency. BPD patients felt significantly less transparent than HCs, but there were no differences in objective transparency. BPD patients tended to underestimate the transparency of their emotions compared to HCs, who in turn overestimated their transparency. This suggests that BPD patients expect that others will not know how they feel, irrespective of how observable their emotions actually are. We link these findings to low emotional awareness and a history of emotional invalidation in BPD, and we discuss their impact on BPD patients' social functioning.
Keywords: borderline personality disorder; emotional arousal; facial expressions; mentalizing; transparency estimation.