What Is Nudge Theory?

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Definition
A method of guiding people's behavior in a predictable direction just by slightly changing how choices are arranged or presented — without bans, mandates, or financial incentives. It's called a "nudge" because it influences people gently, like a nudge with an elbow, while leaving their freedom of choice fully intact.
Proposed by Richard Thaler and Cass Sunstein
Behavioral economist Richard Thaler and legal scholar Cass Sunstein popularized this concept in their 2008 book "Nudge." Drawing on behavioral economics research showing that people do not always choose rationally, they argued that choice architecture could be used to guide individuals and society toward better outcomes.
A Key Nudge Type: Default Options
This involves designing the option that automatically applies when someone makes no active choice. Because people strongly tend to stick with whatever the default is rather than change it, the outcome can shift dramatically depending on which option is set as the default.
Real-World Policy Applications
Countries like Austria and France, which set organ donation to opt-out (automatic consent unless you actively decline), see far higher donation consent rates than opt-in countries, where people must actively sign up. Automatically enrolling employees in retirement savings plans, with the option to opt out if they choose, is another widely cited example of a nudge in policy.
The Concept of Choice Architecture
The order, format, and context in which choices are presented — essentially the environment in which people make decisions — is called "choice architecture." A nudge can be understood as a specific technique that uses choice architecture to steer toward a particular outcome.
Ethical Debate: The Risk of Manipulation
Although nudges are meant to respect individual freedom of choice, critics have consistently raised concerns that they could be misused to manipulate behavior without people's awareness. Mindful of this, Thaler and Sunstein emphasized a guiding condition — sometimes called "libertarian paternalism" — that everyone retains freedom of choice, and that any nudge should serve the interest of the person being nudged.

What Is Nudge Theory?

Nudge theory is an approach from behavioral economics that aims to guide people toward better decisions just by slightly changing how choices are presented, without restricting their freedom of choice. Because it can shape behavior in desirable directions using cognitive biases rather than mandates, prohibitions, or financial incentives, it has become widely used in policy design.

Another Way to Encourage Cooperation

While a nudge shapes an individual's choice environment to steer their behavior, there's also a way to analyze situations where multiple people must decide whether to cooperate or betray one another, using game theory — see our guide to the Prisoner's Dilemma for the conditions under which cooperation tends to emerge.

Frequently Asked Questions

Isn't a nudge just a way of tricking people?

Thaler and Sunstein emphasized that a nudge should fully preserve freedom of choice and serve the interest of the person being nudged. That said, critics consistently point out that, in actual application, this principle can be violated and nudges can be misused to manipulate people.

Do companies use nudges in marketing too?

Yes — techniques like setting a particular option as the default, or highlighting that "many people have already chosen this option," are commonly used to steer consumer choices.