Welcome back to the Coursera course How to Apply the Multiphase Optimization Strategy (MOST) in Your Intervention Development Research. We're in Module 2, "The preparation phase: Laying the foundation for successful optimization." This is Lesson 1, "Basics of the conceptual model." I'm Kate Guastaferro and I'll be your narrator for Module 2. I'm at the College of Health and Human Development at the Pennsylvania State University. I'm one of the developers of this course along with Linda Collins who is at the School of Global Public Health at New York University. In this lesson, we're focused on the preparation phase of MOST which lays the groundwork for optimization. In this lesson, we will define the term "conceptual model" and learn about the critical role it plays in MOST. Let's begin with the definition of a conceptual model. The conceptual model is a causal model of the behavioral, biobehavioral, biomedical or social-structural process to be intervened upon. Drawing from theory, empirical literature and or clinical practice, the conceptual model expresses all of what's known or hypothesized about this process. And it's a description of exactly how the intervention under development is to intervene upon this process. It serves as a visual explanation for the role each candidate component is expected to play in changing behavior leading to the outcome of interest. You might think of the conceptual model as a representation of the engine that drives the intervention. So here is a generic outline of a conceptual model. Looking from left to right across the top, you see the labels for intervention components, proximal mediators and the outcome. The conceptual model links each component with one mediator that's expected to impact short and long term outcomes. Consider this example of a conceptual model for a hypothetical intervention designed to reduce PTSD symptom severity among children who have experienced child maltreatment. On the left, you see five candidate components: relaxation training; emotion regulation; cognitive processing; exposure and response prevention; and acceptance. Each component then targets one respective mediator and the right side of the conceptual model describes how the mediator will affect behaviors in relation to the outcome of interest. The causal flow runs from left to right as the arrow at the bottom depicts. By way of example, you might read this conceptual model to say that the component containing relaxation training techniques is designed to target stress biology impairment, and less impairment leads to reduced PTSD symptoms severity. This is a fairly simple conceptual model example. Theory and empirical literature might necessitate a more complex process to be intervened upon. Take for example, this conceptual model of an intervention designed to decrease sexually transmitted infections among first year college students. Immediately you can see this is much more complex of a causal process than the previous example, but it's oriented similarly. You see intervention candidate components depicted on the left hand side of the conceptual model, but you'll notice what we call a constant component labeled here as "Information." A constant component is one that's not subjected to experimentation. You might consider to include a constant component when there is a base level of knowledge that all participants need, or an ethical standard of care, but there are important conceptions in the inclusion of a constant component, namely because of the optimization trial, experimental design you'll learn more about in the next module, Module 3, it's not possible to ascertain the impact of this constant component on the outcome on its own or how it may impact each of the components that will be manipulated. You'll learn much more about the constant component in Module 5 but for now just know that we encourage you to be thoughtful about the inclusion of the constant component. So we have it depicted here and then the five intervention components depicted in teal. Each of those targets one proximal mediator which you see in blue. Then moving to the right, the theoretical and empirically informed process of behavior change is described through a series of mediators and proximal outcomes leading finally to the distal outcome of interest which here is the decrease in sexually transmitted infections. We've described what a conceptual model is within MOST but let us also be clear about what a conceptual model is not. The conceptual model is not a logic model. A logic model does not link outcomes to activities and the principles of an intervention. A logic model is a good starting point but a conceptual model distinctly details the explicit mechanisms by which the intervention components are expected to effect change. A conceptual model is also not a structural equation model. There are similarities but the conceptual model does not depict every possible statistical relationship among the components, mediators and outcome. These of course may be examined post hoc but remember that the purpose of the conceptual model is to describe the process of change, the engine of the intervention. The conceptual model is of critical importance to the rest of the MOST framework. It's certainly time consuming and challenging. Teams often revise the conceptual model multiple times during a project. It's an iterative process. We fully acknowledge that it's a lot of work, but it is worth it, and you should absolutely never skip this step. The conceptual model is of critical importance as you'll return to the conceptual model at multiple points through the phases of MOST. In the preparation phase, the conceptual model guides the selection of candidate components. In the optimization phase, the conceptual model will inform the experimental design you select for the optimization trial. The conceptual model will be important in guiding the continual optimization process to improve the intervention, and the conceptual model is critical in a compelling grant proposal. It can be very useful to reviewers to understand and visualize how the intervention will change behavior. All of the work you put into the conceptual model can form the basis of a good literature review article. We also strongly recommend that you include your conceptual model in a protocol paper describing your optimization trial. For an example of this, we refer you to the Gwadz et al. (2017) paper. In this lesson, you learned how to define the term conceptual model and to describe the critical role of the conceptual model in MOST. In the next lesson, you'll learn to explain the best practices for developing a conceptual model, specifically the role of theory and empirical findings in its development. We'll discuss the level of specificity needed in a conceptual model and the importance of forward engineering. You'll also learn how to deal with participant heterogeneity. See you then. [MUSIC]