The Science Behind Mental Fitness
Every tool in the 2027 Mental Fitness Diary comes from somewhere: a study, a researcher or a long tradition of people trying to build a life of wisdom and wellbeing.
This page lists the sources behind each month’s chapter in the 2027 Diary, along with a book, a podcast and an article if you’d like to read further.
There's also some additional information on a variety of Mental Fitness topics, elements of our Toolkit, and behavioural design habits.
Reading this page isn't strictly neccessary to enjoy the diary. In fact, it's probably a hindrance. But it’s here if you ever wonder whether we made it all up.
Imagine if you could think about your
Mental Fitness just like your physical fitness.
The References
Explore the research and ideas behind our 2027 diary. Organised by month, these references bring together academic studies, books, podcasts and further reading to help you explore each theme in more depth.
January · Progress By Design
Researcher featured: Peter Gollwitzer. Theme: implementation intentions, or ‘if–then’ plans.
Study: Gollwitzer, P. M. (1999). Implementation intentions: Strong effects of simple plans. American Psychologist, 54(7), 493–503.
Study: Gollwitzer, P. M. & Sheeran, P. (2006). Implementation intentions and goal achievement: A meta-analysis of effects and processes. Advances in Experimental Social Psychology, 38, 69–119.
Book: Milkman, K. (2021). How to Change: The Science of Getting from Where You Are to Where You Want to Be. Portfolio.
Podcast: Social Science Bites: Katy Milkman on behaviour change. SAGE, February 2025.
Article: Halvorson, H. G. (2011). Nine Things Successful People Do Differently. Harvard Business Review.
February · The Way We’re Working Isn’t Working
Theme: strategic rest and recovery.
Book: Pang, A. S.-K. (2016). Rest: Why You Get More Done When You Work Less. Basic Books.
Book: Schwartz, T. (2010). The Way We’re Working Isn’t Working. Free Press. Further reading whose title is echoed in this month’s theme.
Study: Sonnentag, S. & Fritz, C. (2007). The Recovery Experience Questionnaire. Journal of Occupational Health Psychology, 12(3), 204–221.
Podcast: Work Better: The Science of “Aha!” Moments with Alex Soojung-Kim Pang. Steelcase. Transcript.
Article: Schwartz, T. & McCarthy, C. (2007). Manage Your Energy, Not Your Time. Harvard Business Review.
March · Are You Getting What You Need?
Researchers featured: Edward Deci, Richard Ryan and Christina Maslach. Themes: self-determination theory and burnout.
Study: Ryan, R. M. & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. American Psychologist, 55(1), 68–78.
Book: Maslach, C. & Leiter, M. P. (2022). The Burnout Challenge: Managing People’s Relationships with Their Jobs. Harvard University Press.
Book: Deci, E. L. & Flaste, R. (1995). Why We Do What We Do.
Podcast: Making Positive Psychology Work: Richard Ryan on motivation. Michelle McQuaid, episode 56, 2017.
Article: Maslach, C. & Leiter, M. P. (2022). Burnout at work: fix the job, not the person. World Economic Forum.
April · Don’t Believe Everything You Feel
Featured perspectives: David Burns on emotional reasoning, and Stoic philosophy.
Book: Burns, D. D. (1980). Feeling Good: The New Mood Therapy. William Morrow.
Study: Gross, J. J. & John, O. P. (2003). Individual differences in two emotion regulation processes: Implications for affect, relationships, and well-being. Journal of Personality and Social Psychology, 85(2), 348–362.
Podcast: Feeling Good Podcast: How to Crush Negative Thoughts: Emotional Reasoning. David Burns & Rhonda Barovsky, episode 203, August 2020.
Article: Emotional Reasoning. Psychology Tools. Clinician resource.
May · Mind Your Language
Researchers featured: Matthew Lieberman, Lisa Feldman Barrett and Kristin Neff. Themes: affect labelling, emotional granularity and self-compassion.
Study: Lieberman, M. D., Eisenberger, N. I., Crockett, M. J., Tom, S. M., Pfeifer, J. H. & Way, B. M. (2007). Putting feelings into words: Affect labeling disrupts amygdala activity in response to affective stimuli. Psychological Science, 18(5), 421–428.
Book: Barrett, L. F. (2017). How Emotions Are Made: The Secret Life of the Brain. Houghton Mifflin Harcourt.
Podcast: Huberman Lab: Dr. Lisa Feldman Barrett – How to Understand Emotions. October 2023.
Article: UCLA Health (2007). Putting feelings into words produces therapeutic effects in the brain.
June · The Psychology of Hope
Researcher featured: C. R. Snyder. Theme: hope, agency and pathways thinking.
Book: Snyder, C. R. (1994). The Psychology of Hope: You Can Get There from Here. Free Press.
Study: Snyder, C. R. (2002). Hope theory: Rainbows in the mind. Psychological Inquiry, 13(4), 249–275.
Podcast: Hidden Brain: You 2.0 – Fighting Despair. With psychologist Jamil Zaki.
Further reading · provisional reference: Rand, K. L. Hope theory, in The Oxford Handbook of Hope. Oxford University Press. View the supplied reference.
Editorial note for this draft: confirm the June handbook citation and link before publication, or replace it with a suitable general-audience overview.
July · Connecting Under Pressure
Researchers and research featured: John Cacioppo, Julianne Holt-Lunstad, Nicholas Epley and the Harvard Study of Adult Development. Theme: social connection.
Study: Holt-Lunstad, J., Smith, T. B. & Layton, J. B. (2010). Social relationships and mortality risk: A meta-analytic review. PLoS Medicine, 7(7), e1000316.
Book: Cacioppo, J. T. & Patrick, W. (2008). Loneliness: Human Nature and the Need for Social Connection. W. W. Norton.
Book: Waldinger, R. & Schulz, M. (2023). The Good Life. Simon & Schuster.
Podcast: The Science of Happiness: A Cure for Loneliness. Greater Good Science Center, UC Berkeley. With former US Surgeon General Vivek Murthy.
Article: Office of the US Surgeon General (2023). Our Epidemic of Loneliness and Isolation: Advisory on the Healing Effects of Social Connection.
August · Will You Be There for Me When Things Go Right?
Researcher featured: Shelly Gable. Theme: active constructive responding.
Study: Gable, S. L., Reis, H. T., Impett, E. A. & Asher, E. R. (2004). What do you do when things go right? The intrapersonal and interpersonal benefits of sharing positive events. Journal of Personality and Social Psychology, 87(2), 228–245.
Book: Seligman, M. E. P. (2011). Flourish. Free Press.
Podcast · provisional reference: The Science of Happiness: Capitalizing on Positive Events episodes. Greater Good Science Center, UC Berkeley. View the supplied podcast link.
Editorial note for this draft: the supplied August podcast link is identical to July’s. Confirm the intended episode and replace the link before publication.
Article: Capitalizing on Positive Events. Greater Good in Action, UC Berkeley.
September · Why We Need To Be Needed
Researcher featured: Gordon Flett. Theme: mattering.
Book: Flett, G. L. (2018). The Psychology of Mattering: Understanding the Human Need to Be Significant. Academic Press.
Study: Rosenberg, M. & McCullough, B. C. (1981). Mattering: Inferred significance and mental health among adolescents. Research in Community and Mental Health, 2, 163–182.
Podcast: Hidden Brain: Do You Feel Invisible? With Gordon Flett, February 2026.
Article: Cornwall, G. (2023). Want to Believe in Yourself? ‘Mattering’ Is Key. The New York Times. Reprinted by the Association for Psychological Science.
October · Reclaiming Your Attention
Researcher featured: Paul Leonardi. Theme: digital exhaustion.
Book: Leonardi, P. (2025). Digital Exhaustion: Simple Rules for Reclaiming Your Life. Ebury / Penguin Random House.
Study: Leroy, S. (2009). Why is it so hard to do my work? The challenge of attention residue when switching between work tasks. Organizational Behavior and Human Decision Processes, 109(2), 168–181.
Podcast: unSILOed: Paul Leonardi. Episode 615, January 2026.
Article: UC Santa Barbara News (2025). Digital Exhaustion: Paul Leonardi shares how to make technology work for you.
November · The Art of Savouring
Researchers featured: Fred Bryant, Barbara Fredrickson and Rick Hanson. Theme: savouring positive experiences.
Book: Bryant, F. B. & Veroff, J. (2007). Savoring: A New Model of Positive Experience. Lawrence Erlbaum.
Study: Fredrickson, B. L. (2001). The role of positive emotions in positive psychology: The broaden-and-build theory of positive emotions. American Psychologist, 56(3), 218–226.
Podcast: The Science of Happiness: Three Good Things. Greater Good Science Center, UC Berkeley.
Article: 10 Steps to Savoring the Good Things in Life. Greater Good Magazine.
December · Meaning Is the Missing Link
Researcher featured: Michael Steger. Theme: meaning, coherence, purpose and significance.
Study: Martela, F. & Steger, M. F. (2016). The three meanings of meaning in life: Distinguishing coherence, purpose, and significance. Journal of Positive Psychology, 11(5), 531–545.
Book: Frankl, V. E. (1946/2006). Man’s Search for Meaning. Beacon Press.
Book: Esfahani Smith, E. (2017). The Power of Meaning. Crown.
Podcast: The Psychology Podcast: Meaning, Purpose, and Significance with Michael Steger. Scott Barry Kaufman, July 2018.
Article: Three Ways to See Meaning in Your Life. Greater Good Magazine.