Known Knowns and Known Unknowns on Behavior Change Interventions and Mechanisms of Action

Systematic reviews and meta-analyses of research play an important role in summarizing current knowledge on the efficacy of the behavior change techniques and mechanisms of action that comprise behavioral interventions. The current reviews in the science of behavior change (SOBC) special issue represent a ‘step change’ in evaluating current evidence on behavior change interventions and mechanisms. This concluding article outlines the key findings and emerging issues identified in the reviews (‘known knowns’), and summarizes the evidence gaps highlighted by the reviews that need to be addressed in future research (‘known unknowns’). Specifically, findings of the reviews indicate that: tests of mechanisms of behavior change intervention are not routinely conducted by primary studies and research syntheses; intervention study quality is sub-optimal and reviews do not sufficiently account for study quality when assessing intervention effects and mechanisms; substantive variability exists in descriptions of intervention content and putative mediators implicated in their mechanisms of action; limited data is available on the efficacy of many behavior change techniques; and moderators of intervention effects and mechanisms are seldom taken into account. In terms of potential solutions to these issues, we advocate: testing isolated effects of behavior change techniques and associated mechanisms of action; routine evaluation of study quality in behavioral intervention research; development of an evidence base of links between behavior change techniques and theory-based constructs involved in mechanisms of action; adoption of fit-for-purpose methods for synthesizing behavioral intervention mechanisms of action; and routine testing of moderators in intervention research.