The capability–opportunity–motivation–behaviour (COM-B) model. Reproduced from ref. 48. Capability is an attribute of a person that together with opportunity makes a behaviour possible or facilitates it. Opportunity is an attribute of an environmental system that together with capability makes a behaviour possible or facilitates it. Motivation is an aggregate of mental processes that energise and direct behaviour. Behaviour is individual human activity that involves co-ordinated contraction of striated muscles controlled by the brain. Physical capability is capability that involves a person's physique and musculoskeletal functioning (e.g., balance and dexterity). Psychological capability is capability that involves a person's mental functioning (e.g., understanding and memory). Reflective motivation is motivation that involves conscious thought processes (e.g., plans and evaluations). Automatic motivation is motivation that involves habitual, instinctive, drive-related and affective processes (e.g., desires and habits). Physical opportunity is opportunity that involves inanimate parts of the environmental system and time (e.g., financial and material resources). Social opportunity is opportunity that involves other people and organisations (e.g., culture and social norms).