A Computational Phenotype of Disrupted Moral Inference in Borderline Personality Disorder

A social inference model of idealization and devaluation

People often form polarized beliefs, imbuing objects (e.g., themselves or others) with unambiguously positive or negative qualities. In clinical settings, this is referred to as dichotomous thinking or "splitting" and is a feature of several psychiatric disorders. Here, we introduce a Bayesian model of splitting that parameterizes a tendency to rigidly categorize objects as either entirely "Bad" or "Good," rather than to flexibly learn dispositions along a continuous scale. Distinct from the previous descriptive theories, the model makes quantitative predictions about how dichotomous beliefs emerge and are updated in light of new information. Specifically, the model addresses how splitting is context-dependent, yet exhibits stability across time. A key model feature is that phases of devaluation and/or idealization are consolidated by rationally attributing counter-evidence to external factors. For example, when another person is idealized, their less-than-perfect behavior is attributed to unfavorable external circumstances. However, sufficient counter-evidence can trigger switches of polarity, producing bistable dynamics. We show that the model can be fitted to empirical data, to measure individual susceptibility to relational instability. For example, we find that a latent categorical belief that others are "Good" accounts for less changeable, and more certain, character impressions of benevolent as opposed to malevolent others among healthy participants. By comparison, character impressions made by participants with borderline personality disorder reveal significantly higher and more symmetric splitting. The generative framework proposed invites applications for modeling oscillatory relational and affective dynamics in psychotherapeutic contexts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Bayesian Decision-Making Under Uncertainty in Borderline Personality Disorder

Bayesian decision theory suggests that optimal decision-making should use and weigh prior beliefs with current information, according to their relative uncertainties. However, some characteristics of borderline personality disorder (BPD) patients, such as fast, drastic changes in the overall perception of themselves and others, suggest they may be underrelying on priors. Here, we investigated if BPD patients have a general deficit in relying on or combining prior with current information. We analyzed this by having BPD patients (n = 23) and healthy controls (n = 18) perform a coin-catching sensorimotor task with varying levels of prior and current information uncertainty. Our results indicate that BPD patients learned and used prior information and combined it with current information in a qualitatively Bayesian-like way. Our results show that, at least in a lower-level, nonsocial sensorimotor task, BPD patients can appropriately use both prior and current information, illustrating that potential deficits using priors may not be widespread or domain-general.

Focusing on the positive or the negative: Self-construal moderates negativity bias in impression updating

Negativity bias refers to the phenomenon whereby people put more weight on negative information. Although evolutionarily favorable for survival, negative bias in impression processing is detrimental to relationships and cooperation. To explore whether the motivation to maintain relationships, indicated by self-construal, mitigates negativity bias, two studies were conducted. In study 1, participants interacted with three agents (worsened, improved, baseline) in a modified social learning task and evaluated the moral level of these agents. Results showed that positivity bias appeared among interdependent individuals, with larger updating for the improved agent than for the worsened agent. Moreover, interdependent individuals exhibited less immediate decreases toward the worsened agent and steeper increases toward the improved agent than did independent individuals. To validate the results of study 1, we used a narrative description paradigm in study 2. Participants read the behavior descriptions of agents and rated them on morality. The negativity bias was significantly mitigated among individuals with high interdependence, though it did not reverse. These results indicate that interdependent individuals focus more on positive information when others change, yielding a more positive pattern in impression updating. This flexible interpersonal coping strategy can bring advantages to social interaction and cooperation.