Notes
This book gives general information about an everyday habit. It isn't medical advice, and it's no substitute for assessment and treatment where checking has become a condition. The NHS services I mention are those for England as I found them 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, 8, 12, 15, 17, 18, 19 and 22. The Tuesday, the door, the straighteners, the client's email and everything else in the running example are invented.
Before you start. The description of obsessive compulsive disorder, the advice to see a GP or self-refer to NHS talking therapies, the note about checking a baby's breathing and the statement that it's unlikely to improve without treatment are from the NHS pages "Overview" and "Treatment" for obsessive compulsive disorder.
Chapter 3. Van den Hout and Kindt, "Repeated checking causes memory distrust", Behaviour Research and Therapy 41, 2003, pages 301 to 316. Three experiments with healthy volunteers, 39, 40 and 40 people, using a computer animation of a gas stove. Radomsky, Gilchrist and Dussault, "Repeated checking really does cause memory distrust", Behaviour Research and Therapy 44, 2006, pages 305 to 316. Fifty undergraduates, a real stove and a real tap, 19 checking trials. Both used people without a diagnosis, which is the population this book is for. The application to the front door is mine.
Chapter 4. Van den Hout and Kindt as above, for the account of familiarity, conceptual processing and vividness. Coles, Radomsky and Horng, "Exploring the boundaries of memory distrust from repeated checking: increasing external validity and examining thresholds", Behaviour Research and Therapy 44, 2006, pages 995 to 1006. Two studies with a real stove. The summary says the changes appeared after a relatively low number of checks and doesn't give the number, so I haven't.
Chapter 5. Radomsky and Alcolado, "Don't even think about checking: mental checking causes memory distrust", Journal of Behavior Therapy and Experimental Psychiatry 41, 2010, pages 345 to 351. Sixty-two undergraduates. The account of why the replay is tempting is mine.
Chapter 6. Alcolado and Radomsky, "Believe in yourself: manipulating beliefs about memory causes checking", Behaviour Research and Therapy 49, 2011, pages 42 to 49. Ninety-one undergraduates, false feedback on a memory test, urges to check measured by self-report. The suggestion about describing yourself differently is mine.
Chapter 7. Rachman, "A cognitive theory of compulsive checking", Behaviour Research and Therapy 40, 2002, pages 625 to 639. A theoretical paper about clinical checking. Applying the multipliers to everyday checking is my extension. Van den Hout and Kindt, "Obsessive-compulsive disorder and the paradoxical effects of perseverative behaviour on experienced uncertainty", Journal of Behavior Therapy and Experimental Psychiatry 35, 2004, pages 165 to 181. Five experiments. The summary says there were "some indications" that repeated checking reduced the sense of having acted responsibly, and I've kept that hedge.
Chapter 9. Rachman as above, for the three multipliers. That they rise with tiredness and stress is my reasoning.
Chapter 10. Rachman as above, for the self-perpetuating loop. The general pattern of reassurance is described from the cognitive behavioural literature without a specific citation. The observation that doubt follows calm to new objects is mine.
Chapter 11. Muris, Merckelbach and Clavan, "Abnormal and normal compulsions", Behaviour Research and Therapy 35, 1997, pages 249 to 252. One hundred and fifty people, 54.7 per cent reporting rituals. The comparison group were patients with a diagnosis. The NHS description of when checking becomes a condition is from the pages cited above.
Chapter 13. Rachman as above, for the effect of perceived probability. The claim that the one time is almost always a missed once is my observation and hasn't been studied as far as I know.
Chapter 14. Parrish and Radomsky, "Why do people seek reassurance and check repeatedly? An investigation of factors involved in compulsive behavior in OCD and depression", Journal of Anxiety Disorders 24, 2010, pages 211 to 222. Fifteen people with OCD, 15 with depression and 20 controls, interviewed. What I say about photos, apps and the partner's role is my reasoning.
Chapter 16. Alcolado and Radomsky, Rachman, and van den Hout and Kindt 2004, as above. Everything else is my reckoning.
Chapter 20. 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 21. NHS pages as above, including the description of cognitive behavioural therapy with exposure and response prevention and medicine. Everything else in the chapter is my own suggestion.