Theories of change propose how intervention resources and activities might lead to the generation of outcomes. They are sometimes presented diagrammatically as logic models. Realist evaluators and others have suggested that interventions should be theorised in terms of how intervention mechanisms interact with context to generate outcomes. Our own trial of the Learning Together whole-school intervention to prevent bullying set out to define, refine and test such theories in the form of context–mechanism–outcome configurations (CMOCs). We drew on several sources to define our starting CMOCs. These included existing middle range theory. This is scientific theory about the general mechanisms (i.e. not necessarily concerning an intervention) that generate outcomes. This should be analytically general enough to apply to a range of settings, populations and/or outcomes, but specific enough to be useful in a given application. We also used previous research and public consultation to inform our CMOCs.

Robust development of behavior change interventions is based on a sound understanding of the target group, the target behaviors that need to change, the context in which change will occur, the hypothesized mechanisms of change, and the behavior change techniques. Intervention development frameworks advocate a systematic approach to behavior change intervention development. Key tasks include (1) identify and analyze the problem addressed in behavioral terms; (2) identify intervention mechanisms, content, and delivery mode(s) and design a logic model or program theory; (3) develop materials or prototypes (e.g., interface); and (4) test the intervention iteratively through empirical optimization. The tasks apply to both developing new interventions and optimizing existing interventions. The tasks may differ somewhat for digital behavior change interventions (e.g., iterative testing and refinement of early prototypes during development). Depending on time and resources, the tasks can be completed relatively quickly or take considerable time. The current chapter presents key challenges in intervention development and describes potential solutions. Fidelity, feasibility, and acceptability should be considered during all development tasks. The chapter also provides recommendations for advancing the methodology of intervention development and the use of intervention development frameworks and approaches in practice and policy settings.

Efforts to address the major health, environmental, and social threats that can be found across the globe rely on changes in human behavior. Yet identifying effective and efficient ways to change behavior remains a vexing challenge. To meet this need, investigators need to design and evaluate behavioral intervention strategies in a manner that affords the creation of evidence-based guidelines that specify not only whether interventions work but also how and under what conditions. In this chapter, the design and testing of interventions are situated within the experimental medicine approach. This approach leverages the strength of the experimental method to test how behavior change intervention strategies work and to identify the conditions under which they operate effectively. Moreover, it organizes how investigators specify the questions that underlie the study of behavior change interventions and requires them to articulate precisely what intervention strategy they are using, how they think the strategy operates, and the outcomes it generates. Through the systematic use of this approach, evidence will emerge that addresses practitioners’ prevailing concerns directly – what intervention strategy is the most effective and efficient way to address the problem at hand. This chapter provides an overview of how to implement the experimental medicine approach, describes its key features, and addresses the importance of precision and, finally, considers this approach within a broader set of initiatives that have emerged to support a programmatic approach to the design, evaluation, and implementation of behavior change interventions.

This chapter presents a generic, ten-task plan for collaboratively developing, testing, refining, and implementing behavior change interventions. Even carefully designed, expensive interventions can prove ineffective if designers make incorrect assumptions about (1) how a behavior pattern is generated and regulated; (2) how participants or organizations are likely to respond; or (3) how novel personal, interpersonal, or organizational practices can be sustained in situ or over time. Interventionists can be misdirected by assuming that recipients are motivated to change or that motivation is sufficient to evoke change, or that they are choosing reflectively to repeat behavior patterns or that they make choices in an influence-free environment or have just a few everyday life goals. Reliance on any of these assumptions, or the application of simple rules such as educate them, promise rewards, or threaten them, can undermine intervention design from the outset. Interventionists can be effective when they cocreate bespoke, tailored, mechanism-based, interventions that are engaging, rewarding, and sustainable in context. Detailed analyses of mechanism and change processes combined with evidence-based, context-tailored collaborative design is a prerequisite. Success needs to be demonstrable in less expensive efficacy evaluations before investing in large-scale effectiveness trials that provide the evidence base for scaled-up implementation.