You know exactly what to do, and you have known since Tuesday.
The task is three lines long. It matters, and knowing it matters has done nothing for four days. Then at 4:40 pm, with the thing due at 5, your hands move on their own and it is done in nine minutes. If you have ADHD this is your whole week, and there is a name for the pattern.
An ADHD brain starts on four things, and importance is not one of them
An interest-based nervous system is the psychiatrist William Dodson's term for how an ADHD brain decides what to start. Most brains engage on importance: this matters, so I begin. An ADHD brain engages on four other things instead, interest, novelty, challenge and urgency. Importance is not on the list, and knowing a task matters does not start it.
That is the whole idea, and it explains the afternoon above. The email was not interesting, not new, not a game, and nobody was watching. At 4:40 it became urgent, and urgency is on the list.
What it is, and what it is not
The model comes from a clinic, not a laboratory.
Dodson saw adults with ADHD in his practice for decades and wrote down the pattern he kept seeing. That is what the term is: a clinical model built from years of patients. It is not a diagnosis; nobody is tested for an interest-based nervous system. It is not a trial result; no study randomised people and measured it. It is a description a great many people with ADHD recognise on first reading, and we say it at exactly that size and no bigger.
There is a second big model of ADHD, and it deserves the same plain words. Russell Barkley's 1997 theory paper in Psychological Bulletin puts inhibition and executive function at the centre: the trouble is holding back the first response, and with it the working memory, self-talk and planning built on holding back (Barkley, 1997). Barkley describes what the brain cannot hold. Dodson describes what it will start on. They are the same afternoon from two sides: you could not hold the email in mind on Tuesday, and nothing about it made you start on Wednesday.
Neither model is the last word, and neither one needs to be for the afternoon to make sense.
The four, in plain words
We say Dodson's four in plainer words, and we add one every ADHD forum found on its own.
- Urgency is a deadline. Not a date in a calendar. The last hour, when time is almost up and the task becomes the only thing in the room. A 2016 meta-analysis of 21 studies and 3,913 people found people with ADHD discount a delayed reward more steeply than other people, a medium effect; the tasks used money, not work (Jackson and MacKillop, 2016). Far-away things count for little until they are close. The deadline lever.
- Novelty is something new. A new place, a new tool, a new page. An email from last Tuesday is not new, and the same email at a cafe table is a little newer. The novelty lever.
- Challenge is a game. A clock, a bet, a race against your own last time. Not points, because points are counted back at you. The game lever.
- Interest is the one you cannot fake, so we do not try. When a task is interesting you do not need this page. The other three exist for every task with no interest in it.
- And someone there. Not one of Dodson's four, but the one people with ADHD found before anyone named it: a friend on the sofa, a stranger on a call, a body double. The company lever.
A deadline, something new, a game, or someone there. Each one is a lever you can pull on one task, today, without becoming a different person. The pillar page walks through all of them.
Why a to-do list has to know this
Almost every to-do list is built for the importance brain.
It asks you to rank tasks by priority, and priority is importance with a number on it. It shows a due date, a fact. It stores the task and waits for you to care enough. For an interest-based brain, the app has stored the task in exactly the shape the brain does not start on, and then it has one more problem. With ADHD, it is hard to keep a list in your head; a 2013 meta-analysis of 38 studies found adults with ADHD score lower on working memory, the short store for a thought while you use it (Alderson and colleagues, 2013). So the list has to live outside the head, and it has to hand back the four levers, not a ranking.
Translate each lever into a list and you get a short spec. Show the time left, not the date, so urgency arrives at noon and not at midnight. Make the place new sometimes. Offer a race against yourself, never a score. And put something in the room. You were never lazy. The list was speaking a language your brain does not start on.
How Kaapi does it
We built Kaapi as the four levers on one page, and nothing on it ranks by importance.
A time you write in the dump, "by 4pm" or "tmrw", becomes a badge on the task: "3h left", then "1h 20m left" under three hours, filling and darkening in the last two hours. That is the deadline. Every focus session opens on a different sky drawn in code, Fog on hills or Fireflies or Night lake, from a bag with no repeat twice running. That is something new. Turn on "Make it a game" and Timi offers at most one a day, chosen from your list, no menu: Your usual is 12:00. Race it? No points, no leaderboard. That is a game. And Timi sits at the bottom right of the screen and says one line about a real open task every five minutes, settable to sixty, quiet during a session, never a banner. That is someone there.
The founder built it for himself: "I have ADHD. When something interests me, I hyperfocus. That is how I have been shipping code since I was 11. But when a task is boring, I know exactly what to do, and I still can't start. So I built Kaapi." Everything you write stays on your Mac. $9.99 a month or $99 a year, plus tax; you try the whole loop first, then you pay.
Frequently asked questions
What is an interest-based nervous system?
It is the psychiatrist William Dodson's term for how an ADHD brain decides what to start. Instead of importance, it engages on four things: interest, novelty, challenge and urgency. The model comes from decades of clinical work with adults, not from a trial, so it is a description many people recognise rather than a measured result.
Is the interest-based nervous system a real diagnosis?
No. It is a clinical model, a way of describing a pattern, and nobody is tested for it. Dodson's term explains one part of how it feels from inside: knowing a task matters does not start it, and a deadline, something new, a game or someone there does.
How is it different from Barkley's executive function model?
Barkley's 1997 theory paper puts inhibition first: the trouble is holding back the first response, and working memory and planning depend on holding back. Dodson describes what the brain will start on. Barkley says what the head cannot hold; Dodson says what moves the hands. They describe the same afternoon from two sides.
How do I use the interest-based nervous system on my to-do list?
Turn each of the four into something on the page. A time of day on a task instead of a date, so urgency is visible. A new place for a stale task. A race against your own last time, with no score. And someone there, a friend on a call or a body double on your screen. Pull one lever on one task, today.
Sources
- Dodson, W. (updated 2025). How adults with ADHD think: Uncomfortable truths about the ADHD nervous system. ADDitude. additudemag.com/adhd-in-adults-nervous-system. A clinical model from practice, not a trial.
- Barkley, R. A. (1997). Behavioral inhibition, sustained attention, and executive functions: Constructing a unifying theory of ADHD. Psychological Bulletin, 121(1), 65–94. doi.org/10.1037/0033-2909.121.1.65. A theory paper.
- Alderson, R. M., Kasper, L. J., Hudec, K. L., and Patros, C. H. G. (2013). Attention-deficit/hyperactivity disorder (ADHD) and working memory in adults: A meta-analytic review. Neuropsychology, 27(3), 287–302. doi.org/10.1037/a0032371. A meta-analysis of 38 studies; well supported.
- Jackson, J. N. S., and MacKillop, J. (2016). Attention-deficit/hyperactivity disorder and monetary delay discounting: A meta-analysis of case-control studies. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 1(4), 316–325. doi.org/10.1016/j.bpsc.2016.01.007. 21 studies, 3,913 people, d = 0.43; the tasks used money, not work.