Can personality be deliberately changed? Effects of a randomized, placebo-controlled intervention on character strengths and Big Five personality traits

The promise of intentional change in adult personality traits attracts broad interest, even as convincing evidence remains scarce and methodologically challenging. In a preregistered randomized placebo- and waitlist-controlled study with N = 3,434 adults, we tested whether an eight-week online training of a self-selected character strength produces short- and long-term changes in character strengths (states and traits) and Big Five personality traits. Participants in the intervention condition increased targeted strengths states more than both placebo and waitlist control conditions. However, intervention and placebo participants experienced similar gains in targeted strengths traits, extraversion, and agreeableness, as well as similar decreases in neuroticism relative to the waitlist condition. Thus, some effects may result from non-specific aspects of the structured activity. Informants did not observe any between-condition differences in strengths trait change. These findings underscore the importance of using rigorous control conditions in research on volitional personality change.