The limits of simple implementation intentions: Evidence from a field experiment on making plans to exercise

Abstract

Recent large-scale randomized experiments find that helping people form implementation intentions by asking when and where they plan to act increases one-time actions, such as vaccinations, preventative screenings and voting. We investigate the effect of a simple scalable planning intervention on a repeated behavior using a randomized design involving 877 subjects at a private gym. Subjects were randomized into i) a treatment group who selected the days and times they intended to attend the gym over the next two weeks or ii) a control group who instead recorded their days of exercise in the prior two weeks. In contrast to recent studies, we find that the planning intervention did not have a positive effect on behavior. We observe a tightly estimated null effect even though the majority of subjects believed that planning is helpful and despite clear evidence that they engaged with the planning process.

Keywords: Behavioral economics; Exercise; Health behaviors; Implementation intentions; Nudge; Physical activity; Planning.

Appendix Figure 1.. Planning Worksheet for Planning Treatment

Figure 1.

Distribution of Days Visiting Gym by Treatment Status

Figure 2.

Fraction Visiting Gym during Each Day of Planning Period