Exploring Individual Differences in Volitional Personality State and Trait Change: The Role of Motivation and Engagement During a 12-week Intervention

Recent studies suggest that personality traits can be changed through volitional change efforts such as personality interventions. However, there is limited empirical research on which factors explain individual differences in intervention gains. Based on suggestions from recent personality development theories and intervention frameworks, we 1) examined whether achieved personality state changes during an intervention explain differences in the degree of trait change and 2) whether individual differences in change could be explained by participants’ motivation and intervention engagement. The study was based on a 12-week personality intervention with a total of 1,523 participants. Personality states were assessed on a daily and weekly basis, whereas personality traits were measured with self- and observer-reports at the beginning and end of the intervention. Participants who deviated in their states most strongly from their initial trait level also changed more in their trait levels in the corresponding direction. Both state and trait changes were stronger if participants a) were more committed to their change goal, b) believed more strongly in the changeability of personality traits, c) completed more implementation intentions, and d) enjoyed their implementations more (i.e., reinforcement). In contrast, the strength of the desire to change, expected attainability, opportunities identified for practice, difficulty of the implementation intentions, and preference for self-reflection or behavioral practice did not systematically predict change. Taken together, these findings provide support for most of the central components of volitional change theories and can help guide future individualized intervention efforts.