The Fogg behaviour model
A behaviour happens when motivation, ability and a prompt land at the same moment.
Fogg proposes that three elements must converge for a behaviour to occur: enough motivation, enough ability, and a prompt to act. Motivation and ability trade off, so a hard task needs high motivation and an easy one needs little. Without a prompt at the moment both are sufficient, nothing happens.
Motivation against ability
How it shows up in software
The model earns its keep as a failure diagnostic. When a feature is not used, it asks which of the three is missing, and the answer is usually ability. Teams reach for motivation campaigns, emails and incentives, when the flow simply has too many steps. Prompt design covers push, email, in-app nudges and the placement of the entry point itself.
Using it well
- Diagnose before you build: for a behaviour that is not happening, name whether motivation, ability or the prompt is the binding constraint.
- Attack ability first, since removing steps is cheaper and more durable than raising motivation.
- Place the prompt where ability is already highest, which usually means inside the flow rather than in an email.
- Stop prompting a behaviour the user cannot currently perform. A prompt without ability teaches people to ignore your prompts.
Where it turns manipulative
- The model is silent on whether the behaviour is good for the user, and it was written for persuasion. Applied without an independent check on user interest, it optimises compliance.
- Prompt escalation, where a team responds to low conversion by sending more notifications, is the standard failure. It raises short-term taps and burns permission.
- Lowering ability barriers around costly or irreversible actions, such as one-tap purchase or one-tap posting with no undo, is the same lever pointed at the user.
Where you have seen it
Amazon
One-click ordering removes nearly all ability cost at the point where purchase intent is highest.
Headspace
A three minute option sits alongside longer sessions, so low motivation still meets a doable task.
What the research says
- Fogg, 2009Contested
Introduced the model at the Persuasive Technology conference as a design framework for behaviour change systems.
A framework, not an empirical finding. It was not derived from a study and it makes no quantitative prediction, so it cannot be confirmed or falsified as stated. Useful as a diagnostic checklist; treat claims of scientific backing with suspicion.
- Michie, van Stralen and West, 2011Mixed evidence
The COM-B model reached a similar three-part structure, capability, opportunity and motivation, from a systematic review of behaviour change frameworks.
Independent convergence on the shape. It does not validate Fogg's version, and COM-B's own evidence base is mostly in health behaviour.
Grades are a judgement about the evidence, not about how useful the idea is. Plenty of contested effects are still worth knowing, as long as you do not cite them as settled.