Personality interventions are a field of growing interest, because many people want to change aspects of their personality and personality changes may positively impact important life outcomes. Although initial research shows that personality interventions can be successful in eliciting lasting trait changes, the strategies, timing, and context of effective personality interventions remain unclear. A careful examination of how these characteristics predict intervention effectiveness would advance theoretical models of volitional personality change. We used intensive longitudinal data from the Changing How I Live Life Study, a smartphone intervention study designed to decrease participants' neuroticism that combines experience sampling methods and mobile sensing (N = 399; nobs = 39,878; Mage = 25.48 years; 85% female; 47% living in Switzerland). Using these data, we examined the effects of different intervention strategies and their timing and situational context on the proximal outcomes of intervention adherence, intervention satisfaction, and changes in momentary positive affect. Intervention strategies that targeted the state level of neuroticism had more positive effects on people's momentary affect than habit-level strategies, providing novel insights into the mechanisms of successful personality change. Furthermore, effects differed depending on the timing and situational context of intervention prompts, highlighting possibilities of optimizing the timing of personality interventions. For example, people were more likely to adhere to intervention prompts in quieter environments or when at home. Together, these findings inform theoretical models of personality trait change and can be used to guide the development of effective and refined personality interventions. (PsycInfo Database Record (c) 2026 APA, all rights reserved).
Haehner et al. (Mon,) studied this question.