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Defining the COM-B subcomponents

Breaking down the COM-B model into sub-components

Each of the three components of COM-B can be divided into two subcomponents.


Capability is divided into Physical Capability and Psychological Capability.

Physical Capability refers to a person’s abilities arising from their physique and bodily functioning. Examples of Physical Capability are having the manual dexterity to carry out a surgical procedure, or having enough stamina to complete rehabilitation exercises.

Psychological Capability refers to a person’s ability to perform a behaviour arising from their psychological functioning.

For example, in order to give feedback to a patient about their weight status a nurse will need to know about the health risks associated with being overweight (knowledge), how to communicate about a difficult issue with sensitivity (interpersonal skills), and to make a judgement about the best time to raise the issue (decision-making skills). The nurse may also need to reflect on whether his or her skills are in line with best practice and make plans to attend Training if there is a need to improve.


Opportunity is divided into Social Opportunity and Physical Opportunity.

Social Opportunity refers to a person’s opportunity to enact a behaviour relating to the social world they inhabit, including the rules and norms that are operating and social cues. For example, people may be more likely to wear face coverings in enclosed spaces to control the spread of an infectious disease if they see others doing the same thing and are aware that there is strong approval for this behaviour within their community.

Physical Opportunity refers to a person’s opportunity to enact a behaviour that arises from objects and events in their environment, the space they inhabit, the time available or the material and financial resources available to them. For example, adhering to advice to self-isolate during a pandemic may be more difficult for self-employed workers who may not be able to pay their bills if they do not work.


Motivation is divided into Reflective Motivation and Automatic Motivation.

Reflective Motivation refers to psychological processes of conscious planning and decision making. For example, for a person to start cycling to work instead of taking the car they might need to believe that this is an achievable action in which the benefits (e.g. saving money and improving fitness) outweigh the costs (e.g. safety concerns and additional time) and have a clear plan of how they are going to access a bike and the route they will take.

Automatic Motivation refers to motivation that involves a) responding habitually or instinctively, or b) wants and needs arising from emotions or drives. For example, in order for the behaviour of cycling to work to be maintained the person will need to gain a sense of pleasure or satisfaction from the behaviour until such time as the behaviour becomes routine (that is something that is done as a general course of action) and eventually automatic (something we have done so routinely for so long, we don’t even think about it – for example, cleaning our teeth before bed).

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Behaviour Change Interventions: Introductory Principles and Practice

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