Combating influence operations is a major priority of governments, tech platforms, and civil society organizations around the world.¹ Yet policymakers lack good information about the nature of the problem they seek to solve. Empirical research on how influence operations can affect people and societies—for example, by altering beliefs, changing voting behavior, or inspiring political violence—is limited and scattered. This makes it difficult for policymakers to prioritize influence threats, judge whether the problem is getting better or worse, and develop evidence-based solutions.

To assess what is known about the effects of influence operations and identify remaining research gaps, the Partnership for Countering Influence Operations sponsored a systematic literature review by Princeton University’s Empirical Studies of Conflict Project. Laura Courchesne, Jacob N. Shapiro, and Isra M. Thange examined eighty-two studies published between 1995 and 2020.² The review included only those studies that (1) examined a specific population targeted by an influence operation, (2) compared measurable outcomes (behaviors or beliefs) of people exposed versus those who were not, and (3) met minimum standards of statistical credibility. The selected studies covered multiple forms of influence operations—mainly political disinformation, state propaganda, and health misinformation.

The literature demonstrates that certain kinds of influence operations can have measurable effects on people’s beliefs and behavior. But we still lack answers to fundamental questions, like whether and how social media–based operations differ from traditional forms of influence.