1. WORKING PAPER
John Mayne
4 July 2016
The COM-B Theory of Change Model
Introduction
Most interventions seek to change the behaviour of individuals and/or
organizations. Yet surprisingly evaluation of interventions has not made much
use of the quite large literature on behaviour change theories and models. One
review of the literature is by Darnton (2008).
There are exceptions. Bennett’s hierarchy has been used in the evaluation of
education programs (Bennett 1975; Bennett and Rockwell 1995). The hierarchy
includes an imbedded behaviour change model where by changes in capacity of
knowledge, aspirations, skills and attitudes (KASA) are seen as leading to practice
changes. Steve Montague has used the Bennett hierarchy in a variety of
evaluation settings (Montague 2000; Montague and Valentim 2010; Montague
and Lamers-Bellio 2012).
In a recent article (Mayne 2015), I used the NOA (Needs, Opportunities and
Abilities) model of Gatersleben and Vlek (1998) discussed by Darnton (2008) as
a key part of a useful theory of change model. Darnton’s review of behaviour
change models notes a key aspect, namely that all of the capacity change
elements in the models are necessary to bring about behaviour change. How the
capacity change elements are organized and grouped differ among different
models, but are essentially referring to the same set of capacities. The NAO model
argues that needs and opportunities lead to motivation which when combined
with abilities leads to behaviour change.
The COM-B model
In working with the Palladium group, a more recent behaviour change model was
identified that seems even more intuitive and is specifically aimed at
interventions aimed at changing behaviour. Michie, Stralen and West (2011) set
out a COM-B model of behaviour change: behaviour (B) occurs as the result of
interaction between three necessary conditions, capabilities (C), opportunities
(O) and motivation (M).
Capability is defined as the individual’s psychological and physical
capacity to engage in the activity concerned. It includes having the
necessary knowledge and skills. Motivation is defined as all those brain
processes that energize and direct behaviour, not just goals and conscious
decision-making. It includes habitual processes, emotional responding, as
well as analytical decision-making. Opportunity is defined as all the
factors that lie outside the individual that make the behaviour possible or
prompt it. (Michie et al. 2011: 4) [italics added]

2. 2
Their COM-B systems model is shown in Figure 1. Note that both capabilities and
opportunities can influence motivation and all three not only bring about
behaviour change but can also be influenced by the resulting behaviour change,
i.e., there is often a feedback loop from behaviour change to capacity change. If
practice change seen as limited, then there may be a need for more capacity
change work.
Reflecting on Bennett’s KASA model:
• Capability relates to knowledge and skills, and is similar to abilities.
• Opportunity is not in the KASA model (but is in the NAO model).
• Motivation relates to attitudes and aspirations.
Interventions typically address one or more of capabilities, opportunities and
motivation, indeed often just capabilities such as when knowledge and skills are
enhanced through workshops and training. In such a case, the behaviour change
assumptions would have to include an assumption about adequate opportunities
and motivation being in place, since a key behaviour change assumption is that
the capabilities, opportunities and motivation are all present and adequate.
In a theory of change context, for the COM-B model we would have Figure 2.
Further discussion on this type of behaviour-change based theory of change
model can be found in Mayne (2015). Note that Figure 2 includes possible
unintended results that could be triggered by the intervention, and need to be
kept in mind.
Working with the COM-B model
In working with this COM-B generic theory of change model, it was not always
clear how to distinguish among the capacity and behaviour changes and their
associated assumptions. Consider these in turn:
Capabilities
Behaviour
change
OpportunitiesMotivation
Figure 1: The COM-B System Model

3. 3
Behaviour Changes
The behaviour changes are the specific practice changes that occur. These are
usually easy to identify and indeed, to measure.
Behaviour Change Assumptions
Since, based on the model, capacity change ‘will’ lead to behaviour change, it is
not always clear what the behaviour change assumptions should be and indeed if
any assumptions are needed. A distinction in part could be that behaviour change
often takes time to become ingrained and seen as worthwhile, and may involve
feedback between the behaviour and capacity change. Teaching skills is fine, but
then putting them into practice takes time and no doubt some trial and error.
Possible generic behaviour change assumptions therefore could include, the need
for:
Behaviour
Change
Capacity Change
Figure 2: The COM-B Based Theory of Change
Reach &
Reaction
Activities/
Outputs
Direct
Benefits
Improved
Wellbeing
Reach
Assumptions
Capacity Change
Assumptions
Behaviour Change
Assumptions
Direct Benefits
Assumptions
Wellbeing
Assumptions
External
Influences
Capability Opportunity
Motivation
Unanticipated
Results

4. 4
• Sustained leadership
• Other sustained support
• Resources
• Early successes
• Application of new capacities being not too difficult
Capacity Changes
Capacity changes should be the actual changes acquired in capabilities,
opportunities and motivation. These would often be more of a challenge to
measure and to set targets for. There might be behaviour change research
available that could help.
Of more immediate concern, is understanding exactly what these terms mean in
the COM-B model. Michie et al. (2011) define the terms as follows:
“In this ‘behaviour system,’ capability, opportunity, and motivation interact to generate
behaviour that in turn influences these components …
• Capability is defined as the individual’s psychological and physical capacity to
engage in the activity concerned. It includes having the necessary knowledge and
skills.
• Motivation is defined as all those brain processes that energize and direct
behaviour, not just goals and conscious decision-making. It includes habitual
processes, emotional responding, as well as analytical decision-making.
• Opportunity is defined as all the factors that lie outside the individual that make
the behaviour possible or prompt it.” (p. 4)
“Within the three components that generate behaviour, it is possible to develop further
subdivisions that capture important distinctions noted in the research literature. Thus,
• With regard to capability, we distinguished between physical and psychological
capability (psychological capability being the capacity to engage in the necessary
thought processes - comprehension, reasoning et al.).
• With opportunity, we distinguished between physical opportunity afforded by the
environment and social opportunity afforded by the cultural milieu that dictates the
way that we think about things (e.g., the words and concepts that make up our
language).
• With regard to motivation, we distinguished between reflective processes (involving
evaluations and plans) and automatic processes (involving emotions and impulses
that arise from associative learning and/or innate dispositions).” (p. 4)
Capabilities is the more straightforward component comprising skills and
knowledge, and frequently addressed in interventions through training and
workshops.

5. 5
Note though how opportunity is defined. Opportunities include events outside
the individual(s) that make behaviour change possible—including changes in
social norms—or prompt it—such as incentives or sanctions.
Motivation could include new ways of thinking and decision-making. Obviously,
in many cases, new opportunities would trigger enhanced motivation.
Note then that:
• Motivation are internal processes that have changed such as new
realizations, thinking and forms of decision-making,
• Opportunities are external to the individuals and might include reasonable
costs, making the time to learn, changes in social norms, incentives or
penalties.
Capacity Change Assumptions
These assumptions need to be the events and conditions that are needed to bring
about the capacity changes. To some extent, the outputs intending to lead to the
capacity change are precisely those events and conditions, or perhaps more likely
the events.
Generic capacity change assumptions might be that:
• Training is relevant to the setting
• Outputs are sensible
• Messages are understood
• Enabling environment is supportive
• Social norms are supportive
• Incentives are supportive
• Reach, if not specifically included.
Further, assumptions for each of changes in capabilities, motivation and
opportunities need to be addressed or accounted for.
Reach and Reaction
Reach and Reaction are the target groups who are intended to receive the
intervention’s outputs and their initial reaction. In an ex post situation, reach
would be those actually reached which could be different from who were intended
to be reached. The expectation would be that those reached saw or were involved
with the outputs. The expected reaction is that the intervention approach and its
outputs were positively received and deemed worth further consideration.

6. 6
Reach Assumptions
The assumptions here are the events and conditions needed to occur if the
outputs delivered are to reach and be positively received by the reach groups.
Generic reach assumptions could include such things as
• the targeted audience is well defined and can be communicated with,
• the approach and outreach is context sensitive, and
• the outputs are seen as acceptable, and worth considering.
Some examples
I have redone, using the COM-B model, several of the examples I used in earlier
publications. Figure 3 is the nutrition example I used in Mayne (2015). The
changes are in the Capacity and Behaviour Change Assumptions, where the COM
components of capacity change are spelled out.
The second example is the one previously used in Befani and Mayne (2014)
illustrating an intervention to improve girl’s education outcomes, shown here in
Figure 4. Here the intervention is shown as a composite intervention covering
• Pathway 1: engagement with community leaders and parents (PW1),
• Pathway 2: improvement to accommodation for girls in schools (PW2),
and
• Pathway 3: gender sensitive training to teachers (PW3).
Again the explicit use of the COM-B model is evident.
Types of Behaviour Change Interventions
Michie et al. (2011) also identify a classification of types of interventions and
policies that are used to change behaviour, based on a review of the relevant
literature (p. 7). Table 1 lists the types of interventions they identified. Also noted
in the table is which element of the COM-B model the intervention relates to.

7. 7
Behaviour Changes
Mother adopt new
feeding practices
External Influences
• Lower prices for
food
• Other staples
become more
Capacity Changes
Mother acquire new
capabilities about
nutrition benefits and
feeding practices
Reach and Reaction
Mothers with young
children
Direct Benefits
Children consume a
more nutritious diet
Capacity Change Assumptions
1. Capabilities - Nutrition benefits
and feeding practices understood
and relevant
2. Opportunities – Nutritious food
available and affordable
3. Motivation – Mothers want to
improve the health of their children
Reach Assumptions
1. Targeted mothers with young
children reached
2. Approach & material seems
appropriate
Wellbeing Changes
Children’s nutrition
status & health
improves
Figure 3: A Nutrition Intervention Theory of Change
Activities/Outputs
Training & Informing
on Nutrition Benefits &
Feeding Practices
Time line
Behavioural Change Assumptions
1. Mothers make decisions about
children’s food
2. New practices supported by
husbands and mother-in-law
3. Parents see improvements in
children’s health
Direct Benefits Assumptions
1. Practices prove practical
2. No reduction in other
nutritious food intake
Wellbeing Change Assumptions
1. Children have access to health
care

8. 8
Restructuring the information in Table 1, we have Table 2 showing the types of
interventions associated with each COM-B component. This suggest ways of
bring about capacity changes.
Table 1 Possible Types of Behaviour Changing Interventions
Intervention Definition Examples
Education
(Capability)
Increasing knowledge or
understanding
Providing information to promote
healthy eating
Persuasion
(Motivation)
Using communication to induce
positive or negative feelings or
stimulate action
Using imagery to motivate increases in
physical activity
Incentivisation Creating expectation of reward Using prize draws to induce attempts to
Behaviour Change
Girls actively
engaged in learning
Girls’ Behaviour Change Assumptions
A2. Continued support by parents and
community (PW1)
A3. Continued improved teaching that
recognizes improvement in girls’ learning
(PW3)
A4. Girls see their improvement in
learning
Girls’ Direct Benefit Changes
Assumptions
A1. Resources and will continue for
multi-year involvement
Figure 4: Beneficiary Theory of Change for Enhancing Education
Outcomes for Girls
Girls’ Capacity Change
Opportunities-social support, more
time for study; more time with
teachers
Motivation- girls more engaged in
and wanting an education
Direct Benefits Changes
Significantly improved
education outcomes for
girls
Girls’ Capacity Change Assumptions
Opportunities
A5. Girls see the greater support for their
education
A6. Girls relate to the improved teaching
Motivation
A7. Girls realize the importance of getting a
good education (PW1, PW3)
Capabilities
A8. Girls have the inherent capabilities
Outputs
• Teachers provide girls with more
empathetic and supportive teaching in
schools (PW3)
• Improved parental & community
support and time for study (PW1)
Outputs
PW2-Improved
accommodation
Girls’ Capacity
Change
Motivation -Girls
more
comfortable in
school
2 years
4-8 months
4-8 months
Pathway 2 ToC
External
Factors
• Internet
availability
• Text books
become
available

9. 9
Table 2 Types of Interventions Associated with COM-B Components
COM-b Component Types of Interventions
Capabilities Education
Training
Modelling
Enablement
Motivation Persuasion
Modelling
Opportunity Incentivisation
Coercion
Restriction
Environmental Restructuring
Enablement
(Opportunity/
Motivation)
stop smoking
Coercion
(Opportunity/
Motivation)
Creating expectation of punishment or
cost
Raising the financial cost to reduce
excessive alcohol consumption
Training
(Capability)
Imparting skills Advanced driver training to increase
safe driving
Restriction
(Opportunity)
Using rules to reduce the opportunity
to engage in the target behaviour (or
to increase the target behaviour by
reducing the opportunity to engage in
competing behaviours)
Prohibiting sales of solvents to people
under 18 to reduce use for intoxication
Environmental
restructuring
(Opportunity)
Changing the physical or social context Providing on-screen prompts for GPs to
ask about smoking behaviour
Modelling
(Motivation/
Capability)
Providing an example for people to
aspire to or imitate
Using TV drama scenes involving safe-
sex practices to increase condom use
Enablement
(Capability/
Opportunity)
Increasing means/reducing barriers to
increase capability or opportunity
Behavioural support for smoking
cessation, medication for cognitive
deficits, surgery to reduce obesity,
prostheses to promote physical activity
Source: Adapted from Michie et al. (2011: 7)

10. 10
Concluding remarks
The COM-B is an improvement on the previous behaviour change models I have
used in building theories of change. It is more intuitive and more structured,
forcing one to think through the drivers of capacity and behaviour change.
In this note, I have suggested generic types of capacity and behaviour change
assumptions, and Table 2 suggests the types of interventions that can bring about
capability, motivation and opportunity changes.

11. 11
References
Befani, B. and J. Mayne (2014). "Process Tracing and Contribution Analysis: A
Combined Approach to Generative Causal Inference for Impact
Evaluation." IDS Bulletin 45(6): 17-36. Available at
http://onlinelibrary.wiley.com/doi/10.1111/1759-5436.12110/abstract
Bennett, C. (1975). "Up the Hierarchy." Journal of Extension March/April: 8-12.
Bennett, C. and K. Rockwell (1995). Targeting Outcomes for Programs: A
Hierarchy for Targeting Outcomes and Evaluating Their Acheivement,
University of Nebraska. Available at
ftp://bsesrv214.bse.vt.edu/grisso/Program_Logic/Targeting_Outcome_P
rogramming.pdf.
Darnton, A. (2008). Practical Guide: An overview of behaviour change models
and their uses. Available at http://www.civilservice.gov.uk/wp-
content/uploads/2011/09/Behaviour-change_practical_guide_tcm6-
9696.pdf.
Gatersleben, B. and C. Vlek (1998). Household Consumption, Quality of Life and
Environmental Impacts. In Green Households? Domestic Consumers,
Environment and Sustainability. K. Noorman and A. Schoot-Uiterkamp,
Eds. London, Earthscan: 141-183.
Mayne, J. (2015). "Useful Theory of Change Models." Canadian Journal of
Program Evaluation 30(2): 119-142.
Michie, S., M. M. v. Stralen and R. West (2011). "The behaviour change wheel: A
new method for characterising and designing behaviour change
interventions." Implementation Science 6(42): 11 pages. Available at
http://www.implementationscience.com/content/pdf/1748-5908-6-
42.pdf
Montague, S. (2000). "Focusing on Inputs, Outputs, and Outcomes: Are
International Approaches to Performance Management Reaslly So
Different?" Canadian Journal of Program Evaluation 15(1): 139-148.
Montague, S. and K. Lamers-Bellio (2012). "Advocacy Evaluation Theory as a
Tool for Strategic Conversation: A 25 year Review of Tobacco Control
Advocacy at the Canadian Cancer Society." Canadian Journal of Program
Evaluation 24(3): 125-138. Available at
http://evaluationcanada.ca/secure/24-3-125.pdf
Montague, S. and R. Valentim (2010). "Evaluation of RT&D: from 'prescriptions
for justifying' to 'user-oriented guidance for learning'." Evaluation
Research 19(4): 251-261.