Understanding how theories, models, and frameworks complement each other

When it comes to behaviour change, the terms “theory,” “model,” and “framework” often get mixed up, but understanding the distinction between them isn't just semantics—it’s the key to designing interventions that actually stick.

Theories explain why behaviour happens, models break down how it happens, and frameworks help you organise it all into actionable strategies. Getting this right sets the foundation for interventions that move from well-intentioned ideas to measurable impact.

This post is the first in a five-part series exploring the essential tools for understanding and driving behaviour change. Throughout the series, we’ll break down key concepts used in behavioural science and implementation, including determinant frameworks, behavioural models, theories, and the process models that guide intervention design and evaluation. Each post will build on the previous one, taking you step-by-step through the process of diagnosing, understanding, designing, implementing, and evaluating successful behaviour change interventions.

Breaking down the basics: theories, models, and frameworks

Let’s dive into the differences and relationships between these tools. While they may seem like interchangeable jargon, each plays a distinct role in the behaviour change process, and understanding their nuances allows you to apply them more strategically.

Theories: Why behaviour happens

Theories offer explanations—why do people behave in certain ways? Grounded in research, they give us insight into the underlying mechanisms driving behaviour, often through a tested set of ideas. Think of theories as the lens through which we explore root causes.

Example: Theory of Planned Behaviour (TPB) explains how people’s intentions are influenced by attitudes, social norms, and perceived control over the behaviour. Want to predict whether someone will stop smoking or start exercising? This theory is your go-to for understanding the internal drivers at play.

Models: How behaviour occurs

While theories give us the why, models break down the 'how.' Models simplify complex behaviours into digestible pieces, helping us see how the behaviour unfolds. They serve as roadmaps, guiding the design of interventions by showing us which components need attention.

Example: the COM-B model offers a practical way to diagnose what’s blocking or enabling a behaviour. Do people have the capability? Are the resources and opportunities available? Are they motivated? By mapping out these elements, the COM-B model helps us identify exactly where change needs to happen.

Frameworks: Organising and guiding action

Frameworks, on the other hand, are all about structure. They don’t explain or predict behaviour themselves; instead, they provide a way to organise theories and models, guiding the process of designing and implementing interventions.

Example: Behaviour Change Wheel (BCW) integrates insights from multiple models and theories, helping practitioners design interventions through a structured map of strategies. Whether you need to focus on education, persuasion, or regulation, frameworks like the BCW help you organise these strategies into a coherent approach.

Using behavioural models, theories, and frameworks

Theories, models, and frameworks are not isolated tools; they work best when used together to create a comprehensive approach to behaviour change. Each tool contributes a different perspective, and their combined use ensures a well-rounded approach to behaviour change.

Use models to describe and diagnose behavioural challenges

Start with the COM-B model to get a broad sense of what’s driving behaviour—whether it's a matter of Capability, Opportunity, or Motivation. This high-level diagnosis gives you a snapshot of where the barriers might be. But it’s only the first layer.

To go deeper, bring in the Theoretical Domains Framework (TDF), which breaks down those broad COM-B categories into more specific psychological, social, and environmental factors. The TDF identifies domains like Knowledge, Skills, Social Influences, and Beliefs, providing a clearer picture of what exactly is standing in the way of behaviour change. Combining COM-B with TDF gives you both a wide-angle view and a detailed map of the barriers, ensuring that you’re addressing the right issues, both broadly and specifically.

Use theories to explain behaviour

With the diagnosis in hand, the next step is often to dive into why those factors are influencing behaviour. Theories can add an extra layer of insight, helping you understand the psychological drivers behind behaviour, so you can design more targeted and effective interventions.

For example, the Theory of Planned Behaviour (TPB) and Self-Determination Theory (SDT) offer insights into the psychological mechanisms at play—such as attitudes, beliefs, and social norms. These theories help you understand the underlying motivations and thought processes driving the behaviour. By applying these theories, you can tailor your intervention to the psychological and motivational needs of the target group, ensuring it resonates on a deeper level.

Use frameworks to design interventions

Now that you’ve diagnosed the behaviour and understood its psychological underpinnings, it’s time to design an intervention. The Behaviour Change Wheel (BCW) is your guide here. The BCW integrates everything you’ve learned from COM-B and TDF, helping you map out the right strategies to target the specific barriers you’ve identified. It links the diagnosed issues to intervention functions like education, incentivisation, or persuasion, and suggests appropriate Behaviour Change Techniques (BCTs) that will make the intervention practical and impactful.

The BCW ensures that your interventions aren’t just well-intentioned but also systematic, evidence-based, and precisely targeted at the identified barriers, giving you the best chance of success.

Note: the process is not usually as linear as this - the order is imposed here to illustrate the differences!

The takeaway

No single tool—whether a theory, model, or framework—is sufficient on its own:

Theories help us explain behaviour by uncovering the 'why' behind decisions and actions.
Models break down how behaviour occurs, giving us practical tools to target specific elements of change.
Frameworks provide a structural guide, helping you organise concepts and apply them in practice.

Each serves a unique purpose in the behaviour change process, from diagnosing behaviour to understanding its drivers and ultimately designing interventions. By using them in combination, you can create a more effective and tailored approach to behaviour change.

In the next post, we’ll dive deeper into how determinant frameworks like the TDF help diagnose the specific barriers and enablers that shape behaviour, moving us one step closer to implementing successful interventions.

Further reading: This blog series is inspired by the key concepts discussed in the paper "Making Sense of Implementation Theories, Models, and Frameworks" by Per Nilsen, which outlines the role of theories, models, and frameworks in guiding effective behaviour change interventions. For a deeper understanding of these academic foundations, you can explore Nilsen's work on how these tools are used to translate research into practice, understand behaviour, and evaluate implementation outcomes.