According to Thaler and Sunstein (2008, p. 6), a nudge is
any aspect of the choice architecture that alters people’s behavior in a predictable way without forbidding any options or significantly changing their economic incentives. To count as a mere nudge, the intervention must be easy and cheap to avoid. Nudges are not mandates. Putting the fruit at eye level counts as a nudge. Banning junk food does not.
Perhaps the most frequently mentioned nudge is the setting of defaults, which are pre-set courses of action that take effect if nothing is specified by the decision-maker. (See also choice architecture.)
Questions about the theoretical and practical value of nudging have been explored (Kosters & Van der Heijden, 2015). Nudges need to be assessed with respect to their ability to produce lasting behavior change (Frey & Rogers, 2014). Critics have noted that the philosophy behind nudging (liberal paternalism) assumes a human lack of rationality and agency (Gigerenzer, 2015). There may also be limits to nudging due to non-cognitive constraints and population differences, such as a lack of financial resources if nudges are designed to increase savings (Loibl et al., 2016). The limits of nudging speak to the value of field experimentation in order to test behavioral interventions prior to their implementation.
Frey, E., & Rogers, T. (2014). Persistence: How treatment effects persist after interventions stop. Policy Insights from the Behavioral and Brain Sciences, 1(1), 172-179.
Gigerenzer, G. (2015). On the supposed evidence for libertarian paternalism. Review of Philosophy and Psychology, 6, 361-383.
Kosters, M., & Van der Heijden, J. (2015). From mechanism to virtue: Evaluating Nudge theory. Evaluation, 21(3), 276-291.
Loibl, C., Jones, L. E., Haisley, E., & Loewenstein, G. (2016). Testing strategies to increase saving and retention in individual development account programs. http://dx.doi.org/10.2139/ssrn.2735625.
Thaler, R. H., & Sunstein, C. (2008). Nudge: Improving decisions about health, wealth, and happiness. New Haven, CT: Yale University Press.