What Explains Personality Change Intervention Effects?

V olitional personality change interventions have been shown to help people change theircurrent personality towards their ideal personality. Here, we address three limitations of thisliterature. First, we contrast the dominant theoretical perspective of self-improvement withself-acceptance as pathways to reduce the discrepancy between current and ideal personality.Second, we test how well-being aspects change as a by-product of targeting personality.Third, we use a waitlist control group to account for expectancy and demand effects. Acrossthree studies (combined N = 2,094; 1,044 women, 1,050 men; M_age = 30.74, SD_age = 9.57,range_age = 18-75), we implemented randomized online interventions of self-improvement orself-acceptance over a 3-month period, with another follow-up 6 months after baseline and awaitlist control group added in Study 2. Across Studies 1 and 2, participants in bothintervention groups reduced discrepancies between current and ideal personality andincreased in well-being. In both intervention groups, current personality increased, whereasideal personality remained stable. Critically, however, control group participants changedsimilarly, with no significant differences in change compared to participants who received theinterventions. Study 3 compared different control group specifications and highlighted thatthe intervention recruitment framing might have induced selection effects and expectancy anddemand effects leading to positive changes in neuroticism, conscientiousness, andextraversion as well as life satisfaction and self-esteem. Thus, we demonstrate bothshortcomings of previous intervention designs and imprecisions in theoretical frameworks ofpersonality change mechanisms. We discuss future directions including multi-method studies,measurement advances, and micro-randomization of intervention components.