Diagnose before you prescribe with COM-B

Before picking a strategy, identify which of Capability, Opportunity, or Motivation is the bottleneck.

Why it works

Behavior requires all three COM-B components simultaneously — a gap in any one is enough to block the behavior. Interventions matched to the actual gap outperform generic advice because they address the real constraint rather than a plausible-sounding one. The framework works by narrowing the solution space before effort is spent.

How to do it

1. Name the target behavior precisely ("go to the gym three times a week," not "exercise more").
2. Ask three diagnostic questions: Do I know how and am I physically able? (Capability) Do circumstances allow it? (Opportunity) Do I actually want it enough to act? (Motivation)
3. Identify the weakest link — the component scoring lowest — and target that first.
4. Reassess after 2–3 weeks; a fixed bottleneck often reveals the next limiting factor.

Evidence

COM-B is grounded in a systematic review of behavior-change theory synthesis by Michie et al. (2011). Its predictive validity at the individual level is principled rather than independently confirmed by RCTs. (mechanistic)

The model is a consensus synthesis, not an empirical theory derived from experiments. Using the wrong diagnosis still leads to ineffective intervention.

Sources

• Michie, van Stralen & West (2011), "The behaviour change wheel: A new method for characterising and designing behaviour change interventions," Implementation Science

Common mistake

Skipping the diagnosis and defaulting to motivational strategies when the real gap is a skill deficit (capability) or a logistical barrier (opportunity).