Notes
This book gives general information about an everyday habit. It isn't medical or psychological advice, and it's no substitute for a GP or a counsellor who knows you. The NHS guidance I mention is for England as I found it in September 2026.
I've kept sources out of the chapters where I could so they read easily. Here they are by chapter, with the limits I'm aware of. Unless I say otherwise, I read the published summary of each paper and not the full text. I checked each paper for a retraction or correction notice in September 2026 and found none. Where a chapter isn't listed, it rests on my own reasoning. That includes chapters 1, 2, 5, 6, 11, 12, 14, 15, 18, 20 and 23. The household, the pan, the report, the homework and the colleague are invented.
Before you start. The two-week guide for low mood and loss of pleasure is from the NHS pages on depression. The related habit, the scan turned on yourself, is the subject of an earlier book in this series, You wouldn't say it to a friend.
Chapter 3. Wilson and Gilbert, "Explaining away: a model of affective adaptation", Perspectives on Psychological Science 3, 2008, pages 370 to 386. This is a theoretical model with some new tests on pleasant events, and the account of attention going to unexplained, self-relevant events is theirs. The application to a kitchen is mine.
Chapter 4. Rozin and Royzman, "Negativity bias, negativity dominance, and contagion", Personality and Social Psychology Review 5, 2001, pages 296 to 320. Baumeister, Bratslavsky, Finkenauer and Vohs, "Bad is stronger than good", Review of General Psychology 5, 2001, pages 323 to 370. Both are reviews of many studies rather than single experiments. A critique published in 2018 argued that the evidence is less uniform than the reviews claim. The reading of the kitchen as a record unbalanced by count and by weight is mine.
Chapter 7. Kumar and Epley, "Undervaluing gratitude: expressers misunderstand the consequences of showing appreciation", Psychological Science 29, 2018, pages 1423 to 1435. Three experiments with written letters. The extension from letters to something said aloud is mine, and the chapter says so.
Chapter 8. Kumar and Epley, "A little good goes an unexpectedly long way: underestimating the positive impact of kindness on recipients", Journal of Experimental Psychology: General 152, 2023, pages 236 to 252. Field and laboratory experiments with small kindnesses between strangers. The finding about recipients passing kindness on comes from the fourth experiment. The claim that people repeat what's noticed is my reading and not theirs.
Chapter 9. Kumar and Epley 2018 as above, for expected awkwardness. Williams and Bartlett, "Warm thanks: gratitude expression facilitates social affiliation in new relationships via perceived warmth", Emotion 15, 2015, pages 1 to 5. A single experiment with a modest sample and a written note, which the chapter says.
Chapter 10. Wilson and Gilbert as above. Sheldon and Lyubomirsky, "The challenge of staying happier: testing the Hedonic Adaptation Prevention model", Personality and Social Psychology Bulletin 38, 2012, pages 670 to 680. Four hundred and eighty-one students followed for three months after a positive change. The reach from that to the ordinary fine in a household is mine, and the chapter says so.
Chapter 14. Emmons and McCullough, "Counting blessings versus burdens: an experimental investigation of gratitude and subjective well-being in daily life", Journal of Personality and Social Psychology 84, 2003, pages 377 to 389. Davis and colleagues, "Thankful for the little things: a meta-analysis of gratitude interventions", Journal of Counseling Psychology 63, 2016, pages 20 to 31. The effect sizes I describe as modest and small were 0.31 against no treatment and 0.17 against a filler activity, with no difference against a comparison designed to help. Lambert, Clark, Durtschi, Fincham and Graham, "Benefits of expressing gratitude: expressing gratitude to a partner changes one's view of the relationship", Psychological Science 21, 2010, pages 574 to 580. The outcome was the expresser's perception of the relationship, which the chapter says. The NHS page is "5 steps to mental wellbeing".
Chapter 17. Emmons and McCullough, Lambert and colleagues, and Sheldon and Lyubomirsky as above. Running each of them in reverse, to say what the scan costs, is my reasoning and not something any of the papers tested.
Chapter 18. Kumar and Epley 2018 as above, for the recipients' surprise. Everything else in the chapter is my reasoning.
Chapter 20. Lambert and colleagues as above, for expressing against thinking. Kumar and Epley 2018 as above, for the first week. The method is mine.
Chapter 21. The disputed ratio I decline to give is the positivity ratio for couples and teams, which comes from work whose predictive claims have been challenged and which I haven't verified.
Chapter 22. Gollwitzer and Sheeran, "Implementation intentions and goal achievement: a meta-analysis of effects and processes", Advances in Experimental Social Psychology 38, 2006, pages 69 to 119. The rule and its parts haven't been tested together, and what I say to expect is my expectation and not a finding.
Chapter 23. The NHS pages on depression as above.