Nudges use reinforcement and indirect suggestion to get people to recycle more, lower energy consumption, and increase savings rates.
Leonard, T. C. (2008). Richard H. Thaler, Cass R. Sunstein, Nudge: Improving decisions about health, wealth, and happiness. Constitutional Political Economy, 19(4), 356-360.
Reisch, L. A., & Sunstein, C. R. (2016). Do Europeans Like Nudges?.Available at SSRN 2739118.