Abstract
Psychopathy is a multifaceted construct which is characterised by marked impairment across affective, behavioural and interpersonal functioning. The relationship between psychopathy and interpersonal dysfunction is well-researched, particularly in regards to violent offending. However, a large proportion of this research relies on higher-order dimensions, such as factors, facet or domain scores, and neglects to examine the relationships at the lowest level of the trait hierarchy. The current thesis sought to fill this gap in the literature by investigating the associations between the fundamental symptoms of psychopathy and interpersonal dysfunction. This thesis contains three empirical studies, each adopting a multi-method, multi-informant approach and utilising a highly nuanced perspective of psychopathy, the Comprehensive Assessment of Psychopathic Personality (CAPP). The first study was published as a registered report and investigated the associations between the 33 symptoms scales of the CAPP-Self-Report in a large university sample (N = 669). The second study was preregistered on the open science framework and examined the associations between the fundamental symptoms of psychopathy and clinician-rated psychopathy, using the CAPP-Symptoms Rating Scale, in a community sample (N= 250). Finally, the third study directly compared the associations between the symptoms of psychopathy and interpersonal dysfunction across self- and informant-rated psychopathy in each of two aforementioned samples.
Overall, the results of the current thesis provide compelling evidence that the basic traits of psychopathy contribute meaningful and incremental information to the understanding of the relationship between psychopathy and interpersonal dysfunction. Specifically, symptom scales showed correlations of similar magnitude with, and generally explained a higher proportion of variance in, interpersonal outcomes, compared to higher-order dimensions. Additionally, individual symptoms showed distinct relationships with indicators of interpersonal dysfunction, which were attenuated or absent at the higher-order dimension level. These symptom specific associations underscore the importance of considering the fundamental symptoms at the lowest level of the trait hierarchy when exploring the relationship between psychopathy and criterion measures. The specific pattern of associations between symptoms and outcomes varied substantially between methods of psychopathy assessment. These differences could mean that important differences exist in the information gained from each perspective of psychopathy and highlights the need for multiple methods in research on psychopathy. Nevertheless, the current thesis identified traits related to antagonism as possible key drivers of interpersonal dysfunction across methods and samples. Identification of these key drivers of dysfunction could aid in the development of more targeted assessments, formulations, risk predictions, and treatment approaches. Further replication across diverse samples and with alternative psychopathy measures is needed to strengthen the findings of this thesis.