The Power of Autonomy: Self-Selected Goals Outperform Assigned Goals in Reducing Mobile Phone Usage

Behavior change interventions often involve experimenter-assigned goals. We test whether granting individuals autonomy in goal-setting enhances motivation and behavioral change when average goal difficulty and incentives are held constant. In an eleven-week randomized field experiment (N = 149), participants were assigned to either a self-selected goal group (choosing a 10%, 20%, or 30% reduction in daily phone use), an assigned goal group (given a 14% reduction goal, matching the average chosen goal by the self-selected group), or a nogoal control group. Analyses based on over 11,000 daily observations show that, despite identical incentives and comparable average goal difficulty, participants who chose their own goals reduced phone use by 73% more and met their goals 11% more often than those with assigned goals. Greater reductions in phone use and consistent goal achievement were associated with improved well-being: participants in the self-selected condition reported lower depression, anxiety, and perceived addiction at the end of the five-week intervention, with no comparable improvements in the assigned or control conditions. The findings provide causal field evidence on the motivational benefits of autonomy in goal-setting, consistent with Selfdetermination and goal-setting theory.