Investigating personality differences using nuance-level traits and links with health

Abstract

Research on personality differences has been well-established on the levels of broad personality domains such as the Big Five and their more specific facets. Over the past decade, a small number of researchers have proposed that lower-level, more specific personality traits, especially nuances (items), are also of vital importance for personality research, yet nuance-level research has not received sufficient attention. Considering that personality research has been getting broader as well as more fine-grained over time, the structured domains or the Big Five are not sufficient to fit the diversity of research purposes nowadays. Nuance-level research provides a new avenue for research by offering additional information which can supplement the Big Five focused research. This thesis aims to explore whether nuances offer additional useful information above and beyond domains and facets and whether nuance-level research can help to advance understanding of two important research areas in personality: the mechanism of personality differences over time and the association between personality and health outcomes. The data used in this thesis came from five studies: the Ained ja Arenevad Ajud (AAA; Drugs and Developing Brains), the Common-Language California Child Q-Set Study (CCQS), the Life Outcomes of Personality Replication Project (LOOPRP), the HEXACO Online Study (HEXACOS), and the German Revised NEO Personality Inventory validation study (GNEOPIRS).

Results of the empirical studies indicate that lower levels of the personality hierarchy contained substantially more unique information than higher levels which means that nuances provide unique information beyond the information captured by their shared variance that represent broader traits. Thus, aggregating individual traits might result in the loss of useful information which is only offered by nuances (chapter 2). Therefore, nuance-level research could supplement the high-dimensional approaches (domains, and facets) focused research and provide a more complete picture of personality change. This information further allows for the testing of novel hypotheses that rely on systematic between-trait variance in age differences. Based on these findings, this thesis tested some potential mechanisms of personality differences across the life span using nuance-level traits and found that while traits’ self-regulation requirements could not explain personality change, social expectations partially explained personality differences during childhood and adolescence (chapter 3). These findings are further used to test whether they support the social investment theory which has also been proposed to explain personality change based on the maturity principle. The finding that social expectations partially explain personality differences was also evident in young adulthood and results also offered some limited empirical evidence to support the social investment theory (chapter 4). In the last empirical chapter, nuances were used to create personality profiles of health-related lifestyles and outcomes, which allowed for new insights into the covariance structure of these health and wellbeing outcomes. The sixteen outcomes (health-related lifestyles and mental health problems) could be categorized into four groups based on their personality correlations (shared personality correlates): psychological distress, health awareness, emotional control and substance use. The high personality correlations between mental health problems support the hypothesis that co-occurring mental health problems can be partly explained by a general personality-based psychopathology factor, that makes individuals more vulnerable to developing any form of psychopathology.

Overall, the findings of this thesis indicate that nuance-level traits can be useful for personality research, highlighting that it is essential to develop theoretical models specifically for nuance-level personality research. Importantly, this thesis aims to illustrate the possible value of lower-level personality traits, that is nuances, to extend and diversify the field, not to criticize or negate the Big Five focused research.