Recently, I was confronted with an interesting question: what evidence do we have that programme intervention design is best served by using a theory? Do we have concrete data and evidence that using theory leads to more effective interventions?

In my quest for a decent response, I realised that the question isn’t so much why interventions should be informed by theory, but rather, how they should be informed by theory.

According to Dalgetty et al, (2019) “theory provides a coherent and explicit framework for designing, evaluating, and optimising interventions, a common language to aide communication, a means for accumulating evidence over time, and allows predictions in uncertain or new contexts”. But when assessing the role of theory in intervention design, what criteria should we focus on?

A socio-ecological lens is critical

Dalgetty et al (2019) looked at whether there is evidence for the widely accepted view that theory should be the basis for intervention design. Their meta-analysis found that there was no difference in effectiveness between interventions designed using theory and those that did not. Some of the reasons they offer for this lack of evidence include:

  • The wrong theory is selected
  • The theory is not applied as intended and with fidelity
  • The theory does not specify behaviour change techniques, or those that are given are not applied correctly
  • Theory does not specify Forms of Delivery
  • Theory has limited generalizability
  • Theory has limited (intended) range of application

These reasons show that it is critical for practitioners to have a good grasp of how to interpret and apply theory. But there is another important mediating factor, which is that we may not be analysing the full scope of behavioural determinants for a given behaviour. 

In his argument for why behavioural theory has not delivered the desired results (that is, wide-scale, population level behaviour change), Weed (Hagger & Weed, 2019) states that the main reason for this is the sole focus on individual-level behavioural determinants. Using health behaviour change interventions as the example, he argues that “it is known that poor health outcomes, particularly non-communicable diseases, correlate with social deprivation, low employment, poverty, poor housing, and other indices of multiple deprivation. Behavioural theory provides neither the explanation nor, through interventions targeting individuals, the solution to such problems, which must focus on wider causal systems that underpin the social practice and economy of behaviours such as low physical activity and poor diet.”

This argument is very much in line with the frameworks that I tend to gravitate towards. Two favourites are the Behavioural Drivers Model (Petit, 2019) and the SPACE Framework (Schmidt, 2022). Their multi-theory approach also makes them translatable across thematic areas, as their focus is on uncovering the underlying behavioural drivers at various levels of the social ecology, rather than solely focusing on individual-level behavioural drivers. All good behavioural intervention design frameworks take this same multi-theory, socio-ecological approach (see Intervention Mapping and COM-B as well).

“Theory-inspired” versus “theory-based”

One of the long-standing challenges we have in applying behavioural science in global development is the low level of thoroughly reporting the intervention design process. Some of the questions we should be answering in every project report include:

  1. What was the process of identifying key behaviours?
  2. How was formative research conducted to identify the barriers and facilitators?
  3. How were relevant theories identified?
  4. How were barriers prioritised?
  5. How were behaviour change tactics selected?

A well-documented, theory-based intervention, would, at a minimum, be able to answer these questions. In other words, a lack of implementation fidelity will lead to what Hagger (Hagger & Weed, 2019) describes as “theory-inspired interventions [that] pay ‘lip service’ to behavioural theory but fail to link intervention components with relevant theoretical determinants.”

This tells us that the issue is not so much our inability to prove the value of behavioural theory in intervention design, but rather our inability to sufficiently document how we have applied behavioural theory to begin with when we design development-related interventions.

Theory has a role beyond effectiveness

Those who are wary of using behavioural science to design interventions usually look at the role of theory purely from an effectiveness lens. But theory has at least two other roles to play that are vital to intervention success. First, using theory helps to identify the right change methods that have been shown to achieve results (Bartholomew & Mullen, 2011). Without being able to have a reference point of which tactics work for which drivers (whether they are individual, social or policy related), we will find it increasingly challenging to design more innovative and targeted interventions.  Second, using theory helps to measure and describe the pathways through which change is happening (Bartholomew & Mullen, 2011). For us to be able to replicate successes, we need to be able to detail how we got there.

For a list of global development relevant intervention design frameworks, check out this blog post.

Would you say that your interventions have been theory-inspired or theory-based? Share your experiences with me here!

Bartholomew, L. K., & Mullen, P. D. (2011). Five roles for using theory and evidence in the design and testing of behavior change interventions. Journal of Public Health Dentistry, 71(SUPPL. 1).

Dalgetty, R., Miller, C. B., & Dombrowski, S. U. (2019). Examining the theory-effectiveness hypothesis: A systematic review of systematic reviews. British Journal of Health Psychology, 24(2), 334–356.

Hagger, M. S., & Weed, M. (2019). DEBATE: Do interventions based on behavioral theory work in the real world? International Journal of Behavioral Nutrition and Physical Activity, 16(1), 1–10.

Petit, V. (2019). The Behavioural Drivers Model: A Conceptual Framework for Social and Behaviour Change Programming. UNICEF.

Schmidt, R. (2022). A model for choice infrastructure: looking beyond choice architecture in Behavioral Public Policy. Behavioural Public Policy, 1–26.