Peter Haehner

People and their environments continuously shape one another across time. Understanding person-environment transactions is essential for describing, predicting, and explaining the dynamics and development of individual differences. Yet, progress on this has been constrained by two common limitations: study designs driven by practical rather than theoretical considerations and neglecting how person-environment processes unfold across multiple timescales. Here, we present the rationale and design of the My Personality––Wrapped (MPW) Study, a measurement-burst study designed to investigate how individual differences in personality, well-being, attitudes, social and interpersonal behaviors, and health develop and dynamically fluctuate alongside environmental influences across multiple timescales. Across 1 year, participants ( N _max = 1,230) completed baseline (T0) and post-study (T6) assessment batteries, five bimonthly surveys (T1–T5), and 15 pseudorandomly scheduled 1-week bursts comprising mobile sensing, experience sampling, daily, and weekly surveys. This intensive, multi-method study provides comprehensive cross-timescale data on psychological constructs and contextual experiences. The MPW Study is designed to advance the field’s understanding of temporal dynamics underlying individual differences by disentangling within-person processes from between-person differences, facilitating theory development and testing of multi-timescale person-environment transactions, and informing future theory-driven research on the dynamics of personality and well-being, social and health processes, and life disruptions.

Personality traits predict health, well-being, relationship success, and work-related outcomes, but most of the relevant evidence comes from English-speaking populations. The Big Five Aspect Scales (BFAS) are one of the most used English-language personality questionnaires, allowing to assess Big Five domains and aspects validly and reliably. In the present study, we validated German, French, and Italian translations of the BFAS and its short-form (BFAS-40) in a representative sample of Swiss adults (N = 4,492). Across the three languages, the translations of the BFAS and the BFAS-40 showed satisfactory psychometric properties in terms of their factorial validity, reliability, and convergence of short- and long-version. Furthermore, we found partial weak measurement invariance across the three languages for all aspects and domains and strong invariance for some aspects. Finally, in line with existing research, aspects belonging to the same Big Five domain differed in their associations with external variables like political orientation and life satisfaction. The translations of the BFAS and the BFAS-40 may thus facilitate future research on personality traits in non-English speaking samples.

Stress generation describes processes by which individuals actively contribute to the occurrence of self-generated stressful events. Personal characteristics like neuroticism or psychopathology have been found to predict the occurrence of major life stressors over several months or years. However, a profound understanding of stress generation over shorter time periods in people’s daily lives is still missing. Here, we integrated recent research on person-environment transactions from personality psychology into the clinical stress generation literature to develop a process model of stress generation. This process model posits that stress generation unfolds across multiple timescales and that short-term dynamics between momentary, state-level personal characteristics and daily hassles are the building blocks for established long-term stress generation effects. To evaluate a core aspect of this model, we conducted a systematic literature search on stress generation in daily life (45 studies, Ntotal = 9’818). Results show that both dispositional traits and momentary states predict the occurrence of daily hassles, supporting the existence and relevance of stress generation in daily life. However, future research on stress generation across timescales is needed to test the theorized link between stress generation in daily life and long-term stress generation effects.

Many people worldwide want to be less neurotic. As lower levels of neuroticism predict a range of positive life outcomes, including health, work success, and relationship quality, interventions that help people to become less neurotic could have wide ranging impacts. This study protocol describes the rationale and design of the CHILL Study (Changing How I Live Life) that aims to evaluate the effects of a smartphone-based intervention to reduce neuroticism in the general public. The CHILL Study comprises four survey assessments spread over 5 months, a 6-week intervention phase, and two 1-week experience sampling phases without interventions. During the intervention phase, participants who wanted to become less neurotic were randomized to four different treatment groups. These treatment groups differed in the employed intervention strategies that target different aspects and levels of neuroticism. The CHILL Study moves beyond existing research on volitional personality change by testing which strategies most effectively decrease neuroticism and evaluating the longevity and generalizability of intervention-induced neuroticism change via peer-reports, implicit personality assessments, and a 7-week follow-up period. The goals of the CHILL Study are to generate an effective method for decreasing neuroticism and facilitating the development of a comprehensive theory of neuroticism change.

Personality traits have been found to be robust predictors of important life outcomes. However, evidence on longitudinal personality-outcome associations stems almost exclusively from Western countries. It is not yet known if, how, and to what extent personality traits are robustly linked to life outcomes in sub-Saharan Africa. Using data from the Africa Long Life Study, which sampled young adults from Kenya, Namibia, and South Africa (N = 2,770), we examined the Big Two personality traits, agency and communion, as predictors of seven life outcomes (self-reported health, life satisfaction, depression, anxiety, employment status, relationship status, financial situation) 2 to 3 years later. We used specification curve analysis to examine the robustness of personality-outcome associations. Higher levels of agency and communion robustly predicted higher levels of self-rated health and lower levels of anxiety and depression over 2 to 3 years. Furthermore, higher levels of communion predicted being employed 2 to 3 years later. However, personality-outcome associations were smaller than previously observed in Western countries (.02 ≤ |r| ≤ .11) and depended on analytic decisions such as country and the time lag between assessments. Our findings provide novel insights into the cross-cultural replicability of personality-outcome associations.

Many people want to change their personality in some way and personality traits have been found to predict various important aspects of life, including well-being, health, relationship quality, and work success. As a result, volitional personality interventions designed to elicit personality trait change in desired directions have recently gained momentum in research and public discourse. Although the initial evidence on the effectiveness of these interventions is promising, concerns regarding their benefits, risks, and societal implications remain underexplored. In this review, we discuss 10 concerns regarding methodological, ethical, and practical limitations of volitional personality change interventions. Drawing on research across different areas of psychology, we provide a balanced discussion of each concern and outline directions for future research and practical applications of these interventions. Volitional personality change interventions have the potential to improve people’s life and increase satisfaction with the self. However, realizing this potential requires sustained research efforts, thoughtful study design, and careful implementation of these interventions to maximize benefits and mitigate concerns.

Recent meta-analyses and large-scale longitudinal studies have shown that the mean-levels and rank-orders of personality traits change throughout the lifespan. However, people differ from each other in their patterns of personality development. These individual differences in personality trait changes provide important insight into the sources and course of personality development. The present meta-analysis quantified the magnitude of individual differences in personality trait changes and their fluctuation across time lags and age by integrating findings from 229 longitudinal studies (N = 230,492). Results indicated significant individual differences in change in all traits, with neuroticism showing the most pronounced differences, and openness and agreeableness the least. Charting effects across the lifespan, individual differences in change were most pronounced in childhood, decreased during young adulthood, but were significant across the entire lifespan. The age at which individual differences in change were smallest varied across traits, from ages 30 to 75. Finally, individual differences in personality trait changes were larger over longer assessment intervals, for facet-level traits, and among measures that were not designed to examine the Big Five taxonomy. Our findings support theoretical claims that highlight the relevance of genetic and environmental sources of personality development and suggest that individual differences in change endure, challenging the predictions of set-point models of personality development. Moreover, our results provide benchmarks for individual differences in change that can be used to compare the magnitude of differential personality development in future research.

Although personality traits are relatively stable compared to other constructs, comprehensive meta-analyses have shown that the mean-levels and rank-orders of personality traits change throughout the lifespan. In contrast, relatively little is known about whether and how the variance of personality traits develops with age. Examining changes in personality trait variance is, however, critical to contextualize knowledge on mean-level changes, to identify disruptive life phases, to evaluate the changes in predictive utility of personality traits, and to advance personality development theories. The present meta-analysis thus integrated research from 362 longitudinal studies (Ntotal = 398,124) to identify changes in personality trait variance across time and age. We found remarkable stability of personality variance for all traits, indicating that, at the population level, people neither get more different nor more alike across the lifespan. The only deviations from this pattern were variance increases in neuroticism during late childhood and early adolescence (5 to 14 years) and variance decreases in extraversion during middle and late adulthood (45 to 80 years). Notably, though, effect sizes differed substantially across studies and measures. Our results provide novel insights into the lifespan development of personality traits that can be used to advance theoretical frameworks and inform practical applications. Furthermore, by providing benchmark values for the comparison of effect size estimates of future studies (https://personalityresearch.shinyapps.io/VarianceChange/), we aim to facilitate more systematic and cumulative research on variance changes in psychological traits.

Stressful events can trigger mental health problems. Mental health problems, in turn, predict the occurrence of stressful events—a phenomenon called stress generation, which can initiate detrimental cycles between stress and mental health. However, existing research has focused on long-term stress generation. Here, we aimed to advance the understanding of how stress generation unfolds across different timescales by combing experience sampling, daily diary, and 1-month longitudinal data (N = 403). We found that between-person differences in depression, rumination, reassurance seeking, and neuroticism were linked to the occurrence of daily hassles over hours and days and major life stressors over a month. Furthermore, momentary neuroticism and rumination prospectively predicted the occurrence of daily hassles over several hours. Finally, some indicators of hourly and daily stress generation prospectively predicted the occurrence of major life stressors. These findings provide the starting point for a thorough understanding of how stress generation unfolds over time.

Life events like entering a romantic relationship or losing a job have been found to predict changes in personality traits and well-being. However, findings on event-related changes stem almost exclusively from Western countries. Here, we address this limitation by examining event-related changes in agency, communion, life satisfaction, and mental health among young adults living in Namibia, Kenya, and South Africa (N = 3,928). A finding that converged with prior meta-analyses from Western contexts was that childbirth predicted decreases in agency whereas event-related changes in other events diverged substantially from findings in Western samples. For example, finishing education or getting a driver’s license predicted decreases in agency and communion. Furthermore, having first sexual intercourse was associated with decreases in mental health. Future cross-cultural research is needed to test potential explanations for why event-related changes differ across cultural contexts.