Targeting Behavioral Interventions Based on Baseline Motivation Increases Vaccine Uptake

Abstract Behavioral interventions applied to policy problems often yield varying degrees of success in different sub-populations. Understanding and planning for heterogeneous treatment effects is critical to developing nuanced theories of human behavior and offering more useful guidance to policymakers. In this research, we identify one source of heterogeneity in the effectiveness of behavioral interventions: individuals’ baseline motivation to adopt the encouraged activity. Previous studies suggest that people may not take up an activity either because (1) they have no intentions to adopt it or (2) they fail to follow through despite intending to do so. In a series of preregistered experiments (two online and one in the field; total N = 17,362), we tested two approaches to encouraging influenza vaccination, aiming to either change intentions or facilitate follow-through. The information intervention, designed to enhance intentions by targeting misconceptions, increased vaccination intentions and uptake only among those with relatively low baseline motivation. The follow-through intervention, designed to enhance the salience and convenience of getting vaccinated, increased vaccine uptake only among those with relatively high baseline motivation. This work highlights the importance of aligning the mechanisms targeted by an intervention with individuals’ baseline motivation as a fruitful way to customize behavior change interventions.