Fogg Behavior Model

What it is

Most advice about behaviour is advice about wanting it more. Fogg's model is interesting because it treats wanting as only one of three inputs, and the least useful of the three to work on.

The formula is B = MAT. A behaviour happens when motivation, ability and a trigger arrive together and in sufficient quantity. Motivation is how much the person wants the outcome. Ability is how easy the behaviour is for that person at that moment, which is a question about the behaviour rather than about the person's capabilities in general. The trigger is whatever prompts them to do it now. Fogg draws this as a curve, with motivation on one axis and ability on the other, and an Action Line running through the space. A trigger that lands above the line produces the behaviour. The same trigger below the line produces nothing, and Fogg's point about that case is worth keeping: a badly timed prompt does not just fail, it teaches the person to ignore prompts.

Fogg also pairs the possible motivators into three axes: pleasure and pain, hope and fear, acceptance and rejection. Those are the emotional registers a trigger has to land on, and the list is short by design, since a designer who cannot name which register they are appealing to usually has not chosen one.

The asymmetry between the two levers is what makes the model useful rather than merely tidy, and it is the reason it runs the whole Action chapter of Hooked. Motivation is expensive to build. It moves slowly, it costs money, and people notice when it is being manufactured at them, which produces resistance rather than compliance. Ability behaves differently. It can be measured, decomposed into its components, and reduced, one tap instead of three, one field instead of six, no login at all. Removing friction does not persuade anyone of anything. It converts intent that already exists, and it does so invisibly.

Nir Eyal's summary of ability is the flat one: "ability is the capacity to do a particular behavior" (p. 71). The design consequence is that a great deal of what looks like persuasion in modern products is not persuasion. It is subtraction.

This page carries unreviewed, and on this site that describes us rather than the model. Nobody here has assessed the research behind B = MAT, and no study testing the three-factor formula appears in our notes. What can be said without any assessment is what kind of object it is. B = MAT is a model, proposed by a researcher, used as a design heuristic by a generation of product teams. The vault's audit of Hooked records it as a framework and adds the instruction that matters most for anyone citing it: credit Fogg for the model, not Eyal, who applies it.

The reason that instruction is needed is that Fogg is the least visible person in this cluster and the most consequential. He founded the Persuasive Technology Lab at Stanford in the late 1990s, later renamed the Behavior Design Lab, and his classes and workshops trained a large number of the people who went on to build the products the critics write about. Nearly every critique of engagement design is arguing with techniques that were formalised in his laboratory. The critics are famous. The curriculum is not.

In effect

The laboratory, and what it produced

The strongest case connected to this model is a history rather than an experiment, and it should be labelled as one. Fogg's Stanford lab ran classes and retreats through which a large share of Silicon Valley's product culture passed. Eyal attended a retreat at Fogg's home as a Stanford Business School student. A prototype built by Mike Krieger in Fogg's 2007 class on mass interpersonal persuasion became Instagram. Eyal gives that history in Indistractable, pages 92 to 93.

A laboratory whose alumni built successful products is evidence about influence and not about correctness. Products succeed for many reasons, and a curriculum that produced Instagram also produced a great deal that failed and was never written about. The honest claim is that B = MAT has been enormously influential as a design heuristic, and that our notes contain no test of it.

The Obama poster, and the three pairs

Eyal illustrates the motivator axes straight from advertising, on pages 63 to 66 of Hooked. The Obama "Hope" poster runs on hope and fear. Campaigns that sell with sex run on pleasure and pain. A Budweiser spot about belonging and a fear-based motorcycle-helmet public-service advertisement cover the remaining ground, acceptance and rejection, and the darker end of hope and fear.

Set out like this, the three pairs work as a checklist for reading advertising rather than as a theory of motivation. That is roughly the level at which they should be used. They are a taxonomy someone proposed, they are memorable, and no evidence in our notes establishes that motivation divides into these six registers rather than some other set.

Twitter's homepage, 2009 to 2012

The product case is the clearest demonstration of the asymmetry. Between 2009 and 2012 Twitter's homepage went through a shift Eyal documents on pages 80 to 83: the company stopped trying to explain to visitors why they should sign up, and instead made signing up require less. The persuasion was removed and the friction was removed with it.

That is the ability lever pulled in the direction the persuasive-design tradition usually pulls it. The same lever runs backwards, which is the whole design of effort pacts: if ability is cheap to reduce, then adding steps is the cheapest available defence, and Indistractable is in large part an instruction manual for doing to your own environment what Hooked teaches product teams to undo. Same author, same lever, opposite sign.

What it does not say

It is not a tested effect, and this page is definitional. No study in our notes tests B = MAT as a formula. The three factors have no units, no measurement procedure and no stated exchange rate between them, so the model cannot be wrong in any particular case: a behaviour that failed to happen is explained by saying one of the three was insufficient. That is a property of a good design heuristic and a disqualifying property of a scientific claim, and the model is the former.

The Action Line is drawn, not measured. The curve in Fogg's diagram is a way of showing that motivation and ability trade off against each other. It does not come with coordinates, and nobody in our notes has plotted a real behaviour on it.

It does not say motivation is unimportant. The claim is about cost, not about irrelevance. Motivation is one of the three necessary inputs, and the model says a behaviour will not fire without it whatever the ability. Eyal's argument is that a designer facing a choice about where to spend should spend on friction, which is a claim about the designer's budget rather than about the psychology.

The date is uncertain, and our notes say so. The vault records 2009 at medium confidence. Fogg's lab dates from the late 1990s and the underlying ideas were in circulation there well before any single formulation of them, so the year should be read as when our notes place the model rather than as a verified publication date.

The vault does not agree with itself about the Elements of Simplicity. The six factors that decompose the ability leg of B = MAT are described in one place in the vault as Fogg's own diagnostic and in another, the reliability audit of Hooked, as Eyal's elaboration on Fogg's model. That disagreement is unresolved here and is recorded rather than papered over. Anyone citing the six elements should check which of the two books they are actually citing. Elements of Simplicity has no page on this site yet.

Who developed it

B. J. Fogg, a behaviour scientist at Stanford who founded the Persuasive Technology Lab in the late 1990s, later renamed the Behavior Design Lab. The vault records the model at 2009 and medium confidence. He is the most-leaned-on source in the endnotes of Hooked, and the model is his rather than Eyal's, a distinction the vault's audit of that book states explicitly because the popular framing tends to lose it. Fogg has no page on this site yet. Nir Eyal, who applies the model in both Hooked and Indistractable, does.

---