Running head: Personality and Relationship Quality Who Makes Whom Happy in a Romantic Relationship? Contributions to the Predictive Validity of Personality Questionnaires in Mating Contexts. Doctoral Dissertation University of Hamburg Faculty of Psychology and Human Movement Department of Psychology Von-Melle-Park 5, 20146 Hamburg, Germany Inga Grossmann Matriculation Number: 6483333 Email: [email protected] Date of Submission: 25.09.2017 I Personality and Relationship Quality Date of Disputation: 19.03.2018 Vorsitzender des Prüfungsausschusses: Prof. Dr. Alexander Redlich Erster Dissertationsgutachter: Prof. Dr. Burghard Andresen Zweiter Dissertationsgutachter: Prof. Dr. Jan Wacker Erste Disputationsgutachterin: Prof. Dr. Monika Luzi Beyer Zweite Disputationsgutachterin: Prof. Dr. Juliane Degner II Personality and Relationship Quality Abstract Whose romantic relationships last happily? The present work aimed to contribute to the pre- dictive validity of personality questionnaires in mating contexts. Thereby, it refined the un- derstanding of how personality and romantic relationships - particularly their quality - inter- play. Five studies that utilized questionnaires for self-assessing both relationship-related and general personality traits were conducted. Study I and IV focused on predicting relationship quality with the help of methods from ma- chine learning: in both, linear additive models were developed and cross-validated based on different sets of personality variables as predictors. They reproducibly predicted relationship quality to an unprecedented extent. In the four-year longitudinal Study I, variables of rela- tionship-related personality better than those of general personality predicted future relation- ship quality, while actor effects were better predictors than partner, similarity, and other in- teraction effects. In contrast to Study I’s findings, interaction effects (fittings, similarities, other moderators) outperformed actor and partner effects in the cross-sectional Study IV; this may be due to the usage of a novel matching test which was developed and validated success- fully in Study III, thus paving the way to be applied in Study IV and V. The novel economic questionnaire measures one’s own and preferred partner characteristics in a parallel design to enable real-ideal fittings with a current (potential) partner. Just as similarity scores, fitting scores showed high predictive validity in Study III, but were not able to incrementally con- tribute to prediction of relationship quality in the cross-sectional Study IV. Requesting transferability to singles in mating contexts, Study II and V contributed to assess the cross-contextual applicableness of prediction models, which are typically developed on couple’s datasets in anonymous settings. During the four-year-longitudinal Study II, relevant changes of relationship-related personality facets over time and different relationship status- es were tested and described. Unsurprisingly, but still pioneering, many facet changes were relevantly affected by current partnerships and their outcome, while others were not. The findings partly limit the applicableness of models from Study I, which are based on the same personality test. In Study V, answer distortions between an anonymous and a fake online da- ting setting were tested and described. Patterns of self-exaggeration, lower retest-correlations for preferred than for own characteristics, and setting-related differences in predictive validity regarding relationship quality were found. These outcomes partly limit the applicableness of models from Study IV, which are based on the same personality test. III Personality and Relationship Quality Summarized Table of Content 1. General Introduction ________________________________________________________________________ 1 2. Study I: Long-term Prediction of Relationship Quality with Machine Learning by Personality Traits _______ 11 3. Study II: Relationship-related Long-term-stability of Relationship-related Personality Traits ____________ 48 4. Study III: Psychometric Evaluation of Scales for Preferred and Own Personality Traits _________________ 75 5. Study IV: Cross-sectional Prediction of Relationship Quality with Machine Learning by Personality Traits 107 6. Study V: Answer Distortions when Testing Personality Traits in an Online Dating Setting ______________ 129 7. General Conclusion and Contribution ________________________________________________________ 150 Literature__________________________________________________________________________________ 154 List of Figures ______________________________________________________________________________ 165 List of Tables _______________________________________________________________________________ 167 List of Abbreviations _________________________________________________________________________ 169 IV Personality and Relationship Quality Complete Table of Content 1. General Introduction ________________________________________________________________________ 1 1.1. Background ______________________________________________________________________ 1 1.1.1. Relevance of the topic _____________________________________________________________ 1 1.1.2. Reproducible success of previous prediction models _____________________________________ 2 1.1.3. Accuracy- and application-related personality test evaluation _____________________________ 3 1.2. Description of the present work ______________________________________________________ 4 1.2.1. Objectives and conducted studies ____________________________________________________ 4 1.2.2. Data collection ___________________________________________________________________ 7 1.2.3. Own and external contribution _____________________________________________________ 10 2. Study I: Long-term Prediction of Relationship Quality with Machine Learning by Personality Traits _______ 11 2.1. Additional background ____________________________________________________________ 12 2.1.1. Actor-, partner- and similarity effects ________________________________________________ 12 2.1.2. Trait-specific effect of similarities ___________________________________________________ 12 2.1.3. Effects of relationship-related and general personality __________________________________ 13 2.1.4. Gender effects __________________________________________________________________ 13 2.1.5. The present study ________________________________________________________________ 14 2.2. Methods ________________________________________________________________________ 15 2.2.1. Operationalization _______________________________________________________________ 15 2.2.2. Sample _________________________________________________________________________ 18 2.2.3. Procedure ______________________________________________________________________ 20 2.3. Results _________________________________________________________________________ 22 2.3.1. Preliminary analysis ______________________________________________________________ 22 2.3.2. Model performances _____________________________________________________________ 34 2.3.3. Variable importance ______________________________________________________________ 39 2.4. Discussion _______________________________________________________________________ 43 2.4.1. Conclusion ______________________________________________________________________ 43 2.4.2. Limitations and outlook ___________________________________________________________ 46 3. Study II: Relationship-related Long-term-stability of Relationship-related Personality Traits ____________ 48 3.1. Background _____________________________________________________________________ 49 3.1.1. Stability of relationship-related personality traits over time ______________________________ 49 3.1.2. Retest-stability for the Relationship- and Attachment-related Personality Inventory __________ 49 3.1.3. Associations of partnerships to mean-level-changes in personality _________________________ 51 3.1.4. The present study ________________________________________________________________ 51 3.2. Methods ________________________________________________________________________ 52 3.2.1. Sample _________________________________________________________________________ 52 3.2.2. Operationalization _______________________________________________________________ 54 3.2.3. Procedure ______________________________________________________________________ 54 3.3. Results _________________________________________________________________________ 55 3.3.1. Preliminary analysis ______________________________________________________________ 55 3.3.2. Correlates of individual retest-stability _______________________________________________ 59 3.3.3. Overview about facet changes ______________________________________________________ 60 V Personality and Relationship Quality 3.3.4. Figures for significant relationship-related mean-level changes ___________________________ 65 3.4. Discussion _______________________________________________________________________ 67 3.4.1. Main results ____________________________________________________________________ 67 3.4.2. Conclusion ______________________________________________________________________ 68 3.4.3. Possible implications for predicting relationship quality _________________________________ 70 3.4.3. Limitations and outlook ___________________________________________________________ 73 4. Study III: Psychometric Evaluation of Scales for Preferred and Own Personality Traits _________________