A first use of the current context is to inform the content of an intervention option. For example, the language in an activity message might be tailored to the participant’s current location and weather; this would be done to increase the chance that the message is useful for the participant in that context (e.g. location, weather). Thus one role of observations of an individual’s context is to tailor the content of an intervention component message. In many research settings we don’t have access to a large number of participants for our MRT. It is difficult, with small sample sizes, to detect small differences such as whether the contextually tailored activity message should be tailored to both current weather and current location versus only tailored to current weather. Thus the contextual tailoring of messages/suggestions is frequently informed by current behavioral theory, clinical experience and prior studies.

A second use of the context is to learn if some intervention components are more effective in some contexts, e.g., moderation. An MRT can be used to provide empirical data with respect to whether or not a contextual variable moderates the effectiveness of delivering an intervention component. For example, we may find that delivering a contextually tailored activity suggestion is more effective at encouraging activity than no suggestion in a context in which the weather is good. On the other hand, if the current context includes that the current weather is bad, it may make no difference if we deliver a contextually tailored message or not. In this example the intervention component is the tailored activity message component and there are two intervention options: deliver versus do not deliver. Consider another intervention component: planning of physical activity for tomorrow. This component might have three options, the first is unstructured planning, the second is structured planning and the third is no planning. Here we might use an MRT to learn whether the context, such as the participant’s mood at the time of the planning, moderates the effect of the unstructured versus the structured planning in terms of the next day’s physical activity.