营销话术证据 B · meta 分析
21 天就能养成一个习惯
真相
源自 1960 整形外科观察、不是习惯研究；真实中位约 66 天、范围 18-254 天 (Lally 2010)。
机制速览
21 天养成一个习惯，流传很广。它来自 1960 年一位整形外科医生（Maltz）的观察：病人适应自己的新长相，大约要 21 天。那不是一项习惯研究。
来源（2）
- Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W., & Wardle, J. (2010). How are habits formed: modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998-1009. Tracking daily behaviors over 84 days, time to reach automaticity had a median of about 66 days (range about 18-254); missing a single opportunity did not meaningfully impair formation.
- Linardon, J., & Mitchell, S. (2017). Rigid dietary control, flexible dietary control, and intuitive eating: differential relationships with disordered eating and body image. Eating Behaviors, 26, 16-22. Cross-sectional, 372 community adults. Rigid dietary control was associated with more disordered eating; intuitive eating uniquely and consistently predicted less disordered eating and fewer body image concerns; flexible control was mixed (higher body image concerns, and lower disordered eating only once rigid control was accounted for).