Control Systems Model of COM-B Simulator: Physical Activity & Sedentary Behaviour
*COM-B: Capability, Opportunity, Motivation & Behaviour is a well-established behaviour change meta-model.Behaviour is hard to change because capability, opportunity and motivation don’t act in isolation, they build on one another and feed back over time. This interactive simulation reframes the well-established COM-B behaviour-change framework as a control system: each construct behaves like a tank that fills and drains, connected by flows whose strength reflects how strongly one construct drives the next. You can move the levers of a behaviour-change intervention and watch, in real time, how physical activity and sedentary behaviour respond; not as a single before-and-after value, but as a dynamic trajectory that can accelerate, plateau, or relapse.
The purpose is exploratory and educational: to make the dynamics of behaviour change visible and testable. Rather than treating capability, opportunity and motivation as static predictors, the model shows how an intervention ripples through the system, where the leverage points sit, and why the same programme can lead two people to very different outcomes. Relationship strengths between constructs are anchored to effect sizes reported in the peer-reviewed literature, while the temporal dynamics (how quickly each construct responds and how strongly habit feeds back) are illustrative and fully adjustable. It is a tool for building intuition and generating hypotheses, not a validated individual-level predictor.
What you can explore
- Construct tanks: Capability, Opportunity and Motivation, the three drivers of behaviour, shown as reservoirs that fill and drain.
- Behaviour outputs: Physical Activity and Sedentary Behaviour, modelled as two separate outcomes rather than simple opposites.
- Intervention levers: inputs that feed each construct: skills and self-regulation, social and environmental support, and goal-setting and motivation.
- Flows and feedback: connecting pipes whose thickness reflects the strength of each relationship, including a learning loop where behaviour feeds back to reinforce capability.
- Real-world variability: the intention–behaviour gap, environmental disturbances (including a one-off “life shock”), habit strength and day-to-day noise, representing the substantial share of behaviour these constructs alone don’t explain.
- Scenario presets: ready-made intervention profiles for quick comparison.