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Change Management, Systems Thinking

Capability, Opportunity and Motivation interact to generate behaviour: the COM-B Model

One of my favourite models for human behaviour change is Dr Susan Mitchie’s Behavioural Change Wheel and COM-B. She created the COM-B model from a 2011 study of peer-reviewed papers on behaviour change. She concluded: “Interventions and policies to change behaviour can be usefully characterised by means of a Behaviour Change Wheel comprising: a ‘behaviour system’ at the hub, encircled by intervention functions and then by policy categories.

Michie BCW 2011

Behaviour Change Wheel: Michie et al 2011

In the COM-B model, Capability, Opportunity and Motivation interact to generate behaviour. Capability and Opportunity address the question of whether a person can or can’t adopt a particular behaviour while Motivation addresses will they or won’t they adopt it. Capability covers a person’s psychological and physical capacity to adopt a particular behaviour. Opportunity relates to all the external factors that make a behaviour possible. Motivation covers the thought processes that direct behaviour. Both capability and opportunity can influence motivation; for example (but VERY simplistically), if someone understands the importance of a particular health screening programme and it is available nearby, they may be more motivated to participate in it.

Coercion vs. incentives

COM-B provides a way to design interventions aimed at changing behaviour. Michie’s work has created a taxonomy of 93 behaviour change techniques (BCTs), drawn (primarily) from work in public health. The model also differentiates between “interventions” (activities aimed at changing behaviour) and “policies” (actions taken by authorities to enable interventions). So, for example, introducing new legislation is a policy approach with the intervention typically being focused on coercion or restriction. This approach to restrict behaviour relies on the behavioural change technique of “future punishment” (if you don’t comply, you will be punished). Interestingly, a 2019 paper by Mitchie reported that coercion and restriction were the least cost-effective interventions in a public health setting, while the use of incentives was more cost-effective.

Michie also points out that interventions operate within a social context and should be evaluated against 6 criteria (abbreviated to APEASE):

Criterion Description Example questions to answer
Affordability An intervention is affordable if it can be delivered within an acceptable budget to all those who should benefit. What is the budget to implement the proposed intervention and ensure it is working as intended?
Practicability An intervention is practicable if it can be delivered and implemented as designed. Who will implement the proposal?
Effectiveness and cost-effectiveness Effectiveness refers to the effect size of the intervention in relation to its objectives. Cost-effectiveness is the ratio of an intervention’s effect to its cost. Does the evidence support the recommendations for the intervention?
Acceptability Acceptability refers to the extent to which an intervention is judged to be appropriate by relevant stakeholders (and this may differ for different stakeholders). What are the views of different stakeholders and have they all been considered?
Side-effects An intervention may have unwanted side-effects or unintended consequences. What might be the unintended consequences or displacement actions?
Equity An intervention may reduce or increase the disparities between different potential beneficiaries. What will be the effect on other people or other groups?

The Quality Guru Joseph Juran said: “If you always do what you always did, you’ll always get what you always got”. Is it time we took a more behavioural and systems-oriented approach to look at why so many business improvement initiatives (“Change Programmes”) aren’t working or are not working fast enough?

I’ve written before about the need to change the situation to change behaviour, and this ties in very neatly with the idea of BCTs and the Behaviour Change Wheel.

Read also about my favourite Change Models.


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