People say it all the time: be thankful. Posters, songs, and holiday cards all repeat it. It sounds nice, but nice advice can still be wrong. For a long time, nobody ran a real test. Then scientists did.
Sources
Davis et al., "Thankful for the little things: A meta-analysis of gratitude interventions," Journal of Counseling Psychology, 2016
Emmons & McCullough, "Counting blessings versus burdens," Journal of Personality and Social Psychology, 2003
Greater Good Science Center, UC Berkeley — gratitude research summaries
Seligman, M. E. P., Steen, T. A., Park, N., & Peterson, C. (2005). "Positive Psychology Progress: Empirical Validation of Interventions." American Psychologist, 60(5), 410-421. — the gratitude-visit study behind screens 12-16 and 23
Cregg, D. R., & Cheavens, J. S. (2020). "Gratitude Interventions: Effective Self-help? A Meta-analysis of the Impact on Symptoms of Depression and Anxiety." Journal of Happiness Studies, 22, 413-445. — the k=27 / N=3,675 review behind screens 2 and 41
Wood, A. M., Joseph, S., Lloyd, J., & Atkins, S. (2009). "Gratitude influences sleep through the mechanism of pre-sleep cognitions." Journal of Psychosomatic Research, 66(1), 43-48. — the 401-adult sleep survey behind screens 37-40
Algoe, S. B., Haidt, J., & Gable, S. L. (2008). "Beyond reciprocity: Gratitude and relationships in everyday life." Emotion, 8(3), 425-429. — the sorority gift-week study behind screens 27-28
Algoe, S. B. (2012). "Find, Remind, and Bind: The Functions of Gratitude in Everyday Relationships." Social and Personality Psychology Compass, 6(6), 455-469. — the theory behind screens 25-26
Kumar, A., & Epley, N. (2018). "Undervaluing Gratitude: Expressers Misunderstand the Consequences of Showing Appreciation." Psychological Science, 29(9), 1423-1435. — the letter-prediction experiments behind screens 31-32
Watkins, P. C., Scheer, J., Ovnicek, M., & Kolts, R. (2006). "The debt of gratitude: Dissociating gratitude and indebtedness." Cognition & Emotion, 20(2), 217-241. — behind screens 33-36
Boggiss, A. L., Consedine, N. S., Brenton-Peters, J. M., Hofman, P. L., & Serlachius, A. S. (2020). "A systematic review of gratitude interventions: Effects on physical health and health behaviors." Journal of Psychosomatic Research, 135, 110165. — the first 2020 review on screen 43
Jans-Beken, L., Jacobs, N., Janssens, M., et al. (2020). "Gratitude and health: An updated review." The Journal of Positive Psychology, 15(6), 743-782. — the second 2020 review on screens 43-44
Sheldon, K. M., & Lyubomirsky, S. (2012). "The Challenge of Staying Happier: Testing the Hedonic Adaptation Prevention Model." Personality and Social Psychology Bulletin, 38(5), 670-680. — the HAP model on screen 24
Allen, S. (2018). "The Science of Gratitude." White paper prepared for the John Templeton Foundation by the Greater Good Science Center at UC Berkeley. — the source of the two-step definition on screen 4 (currently listed only as the vague "Greater Good Science Center, UC Berkeley — gratitude research summaries")
Read end to end and corrected: August 9, 2026. Numbers checked: August 9, 2026.