We study experimentally when, why, and how people intervene in others’ choices. Choice Architects (CAs) construct opportunity sets containing bundles of time-indexed payments for Choosers. CAs frequently prevent impatient choices despite opportunities to provide advice, believing Choosers benefit. They violate common behavioral welfare criteria by removing impatient options even when all payoffs are delayed. CAs intervene not by removing options they wish they could resist when choosing for themselves (mistakes-projective paternalism), but rather as if they seek to align others’ choices with their own aspirations (ideals-projective paternalism). Laboratory choices predict subjects’ support for actual paternalistic policies.

We propose and develop a dynamic theory of endogenous preference formation in which people adopt worldviews that shape their judgments about their experiences. The framework highlights the role of mindset flexibility, a trait that determines the relative weights the decision-maker places on her current and anticipated worldviews when evaluating future outcomes. The theory generates rich behavioral dynamics, thereby illuminating a wide range of applications and providing potential explanations for a variety of observed phenomena.