Psychotic-Like Reasoning Styles in Patients With Borderline Personality Disorder? An Experimental Investigation of...

Patients with borderline personality disorder (BPD) commonly display psychotic symptoms such as hallucinations or delusional/paranoid ideas. We used the fish task to investigate cognitive biases (jumping to conclusions and overcorrection) implicated in the aetiology of psychotic symptoms in patients with BPD.

Participants received consecutive pieces of information to determine which of two lakes a fisherman was catching fish from. Outcome measures were draws to decision and frequency of premature decisions after just one and after not more than two fish (jumping to conclusions), probability estimate at the time of the decision (decision threshold) and adjustment of the probability estimate after receiving disconfirmatory information (overcorrection). With data aggregated from multiple studies, a total of 170 patients with BPD and 72 healthy controls (parallelized by age, gender and education) participated.

The two groups showed similar draws to decision and frequencies of premature decisions. The decision threshold was also comparable across the groups. However, the patients with BPD showed overcorrection.

The experimental study found no evidence for a jumping to conclusions bias or a lower decision threshold in patients with BPD. The stronger adjustment of probability estimates (overcorrection) in patients with BPD is compatible with the unstable affect, self-image and interpersonal relationships observed in patients with BPD.