Mechanisms of Action

What are Mechanisms of Action?

Interventions within home visiting are comprised of many different techniques to promote specific behaviors that lead to intended outcomes. These techniques affect outcomes through changes in modifiable constructs known as mechanisms of action (MoAs). MoAs are derived from behavioral theory, and are the processes, or mediators, through which specific intervention techniques influence behavior and, through this, achieve intended outcomes.  

Home visiting interventions often aim to influence behavior through changes in MoAs such as maternal beliefs about capabilities (e.g., self-efficacy), skills, motivation, and environmental context and resources. 

Consider the examples below. In the first example, a home visiting program aims to prevent poor birth outcomes for the pregnant enrollees that they serve. Smoking is a known risk factor for preterm birth and a behavior that home visitors select for change. One technique a home visitor may use is to provide the pregnant person with information about the health consequences of smoking for themselves and the fetus. Providing and discussing this information acts to influence their decision to reduce or stop smoking by changing their beliefs about the consequences of smoking.

In the second example, a home visiting program aims to promote secure infant/caregiver attachment. One technique a home visitor may use to accomplish this is to demonstrate positive responses to a crying infant. By demonstrating responsiveness to an infant’s distress, the home visitor gives the caregiver an observable example to imitate, thereby increasing the caregiver’s positive responses to their child’s distress and promoting secure attachment.

In the final example, a home visiting program aims to prevent child injury. One technique a home visitor may use is to provide safety measures like stair gates and outlet covers. Providing resources to alter the home environment offers an opportunity for the caregiver to take precautions to improve home safety for the child.

Why are Mechanisms of Action Important in Designing and Studying Home Visiting Interventions?

MoAs are important because they provide the theoretical link that explain how and why specific intervention techniques will lead to a program’s intended outcomes.

It is important to consider MoAs in studying home visiting interventions to understand how and why a program succeeds or fails to achieve intended outcomes overall and for different subgroups of the families it serves. Understanding how well a program’s interventions target relevant MoAs is key to understanding how to broaden and strengthen its impact on outcomes. Without this understanding, it is hard to know how to refine the program’s interventions.

How HARC is Developing the Mechanisms of Action Taxonomy

The MoA offers a shared language to make it easy to communicate with one another in designing and testing interventions, and to accelerate what the field can learn across different interventions and across different studies of them. To develop the MoA taxonomy, the HARC research team began with the taxonomy developed by the Human Behaviour Change Project, which contains 26 MoAs. HARC carried out five steps to assess and improve the usefulness of original taxonomy for home visiting intervention design and research.

1. We surveyed 73 intervention researchers, asking them to rate the clarity of each MoA’s label and definition, the distinctness of each MoA from other MoAs, the relevance of each MoA for home visiting, and the comprehensiveness of the full list of MoAs (view results).
2. We used survey results to revise MoA labels and definitions.  
3. We surveyed researchers a second time to assess how well the revisions improved the clarity and distinctness of the MoAs.
4. We used results of the second survey to make final revisions to MoA labels and definitions.
5. We surveyed representatives from 17 evidence-based and emerging home visiting models to assess the comprehensiveness of the list of MoAs and the relevance of the MoAs to their model.

The current MoA taxonomy reflects refinements made based on what we learned from researchers and representatives of evidence-based models.