Field experiment on physical activity at ITESO
Objectives: To investigate the efficacy of a social norms communication strategy designed to increase people’s adherence to physical exercise. Study design: A field experiment. Methods: A sample of 173 persons from a Mexican university was randomly assigned to three groups of almost equal size. During nine weeks, members in each group received two different treatments: 1) a weekly message informing them about the number of days they had attended the gym the week before (descriptive messages) and 2) a weekly motivational phrase tailored according to their previous attendance level. The 57 persons comprising the control group received weekly phrases unrelated to physical activity. The estimation technique was a difference-in-difference model. Results: For people who already developed the habit of exercising, descriptive messages did not persuade them to improve their attendance to the gym because they deemed they had exceeded their weekly exercise quota. On the contrary, motivational messages did improve attendance of high performers, demonstrating their power to reinforce healthy lifestyles. Conclusions: non-rational motivations, particularly those inspired in social norms theory, can be useful instruments to reinforce healthy habits.