| Abstract: | A 3-month experimental online study examined the short-term and 1 month follow-up effects of regularly practicing one of two cognitive interventions on subjective well-being. Participants were 435 self-selected adults (366 female, 69 male, aged 18–63) randomly assigned to one of three conditions: writing about best possible selves in the future (n = 135), making gratitude lists (n = 150) or writing to-do-lists as a control condition (n = 150). The study was fully self-administered and exercise instructions were given in online videos. Repeated-measures MANOVA revealed that both interventions significantly increased subjective well-being in comparison to the control condition. Effect sizes for the different components of subjective well-being ranged from r = .09–.13 (η2 = .01–.02) for the 2 months intervention period. These effects were maintained until the 1-month follow-up. Enjoyment and interest regarding the exercise as indicators of perceived person-intervention-fit moderated the effect; participants of the happiness interventions who perceived a better fit showed greater increases in subjective well-being. These findings confirm previous research on these interventions and encourage further studies on online interventions, especially regarding possibilities to increase participants’ motivation and reduce dropout attrition. |
