Degree Name

Doctor of Philosophy


School of Psychology


Background: Borderline personality disorder (BPD) is associated with difficulty forming trust and maintaining cooperation in trust-based exchanges, but little is known about how the disorder influences the temporal ebb and flow of trust, and what aspects of the disorder might be responsible for these trust patterns. An economic game paradigm, the trust game (TG), was used to examine the trajectories of trust as it formed, dissolved, and restored in response to trust violation and repair. Study 1 examined how these trust patterns varied as a function of the number of BPD traits endorsed. Study 2 investigated whether insecure attachment style, self-protective beliefs, and feelings of rejection moderated the effect of BPD trait count on these trust patterns. Study 3 explored how the social-cognitive reasoning for the decisions made during the TG – before, during, and after the trust violation and repair – varied based on the level of BPD trait count.

Method: In all three studies, young adults (N=234) played a 15-round TG in which partner cooperation was varied to signal trust violation and repair, resulting in three phases of trust: formation, dissolution, and restoration. Following the TG, participants were asked to provide the reasoning behind the decisions that they and their partner made. In Study 1, discontinuous growth modelling (DGM) was employed to first model the trajectory of trust during these phases, and the magnitude of the changes in trust in response to the violation and repair, and second, to examine how these trust patterns were influenced by BPD trait count. Study 2 extended the DGM by examining whether the effect of BPD trait count on the levels and trajectory of trust was modified based on attachment style (fearful or preoccupied), endorsing the belief that pre-emptive action should be taken to protect oneself from others, and pre-existing feelings of rejection. In Study 3, 16 of the participants with a high BPD trait count (7-10 traits) and 16 randomly selected, age and gender matched participants with a low BPD trait count (0-2 traits) were asked to provide reasons to explain their own and their partners behaviour during the TG. These reasons were subsequently categorized and compared for between-group differences across each phase of the game.

Results: In Study 1, BPD trait count was associated with an incongruous pattern of trust behaviour in the form of declining trust when interacting with a new and cooperative partner, and paradoxically, increasing trust following multiple instances of trust violation by that partner. BPD trait count was also associated with trust restoring at a faster rate than it was originally formed. Results from Study 2 suggest that the slower rate of trust formation associated with BPD trait count was accounted for by pre-existing feelings of rejection and self-protective beliefs, each of which predicted a slower rate of trust growth. In contrast, endorsing a preoccupied attachment style was found to temper the trust-negating effect of BPD trait count when trust was forming. The faster rate of trust growth in response to trust violations associated with BPD trait count was no longer significant after self-protective beliefs were accounted for, but the latter’s effect on trust during this phase did not reach significance. Study 3 found that during trust formation, the high BPD trait group more frequently attributed negative characteristics to the other player and described their own behaviour as a tit-for-tat strategy despite reasoning that their partner was responding with positive reciprocity. Notably, they articulated these reasons markedly less during the restoration phase compared to the formation phase. Both groups provided similar reasons to describe behaviour during the dissolution phase. Overall, the high BPD trait group was also more likely to say that they did not know why they or the other player made the decisions that they did.

Conclusions: The studies in this thesis adopted an innovative methodological and analytical approach to illustrate both behaviourally and cognitively how relational disturbances may play out in trust-based interpersonal exchanges for those with a high BPD trait count. Interestingly, the studies revealed a paradoxical style of relating where cooperative partner behaviour elicited less trusting behaviour and more hostile reasoning by those with high levels of BPD traits. In contrast, these individuals appeared to engage in more trusting behaviours in response to trust violation, but this phenomenon requires further investigation. Interventions which focus on improving the capacity and accuracy of social-cognitive reasoning may address the trust-related interpersonal difficulties associated with BPD. In particular, exploring themes of rejection and the need to self-protect may provide further insight into these incongruous trust behaviours.

FoR codes (2008)

110319 Psychiatry (incl. Psychotherapy), 1701 PSYCHOLOGY, 170106 Health, Clinical and Counselling Psychology, 170202 Decision Making



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.