Nudge: Improving Decisions about Health, Wealth, and Happiness is a book written by University of Chicago economist and Nobel laureate[1] Richard H. Thaler, and Harvard Law School professor Cass R. Sunstein, first published in 2008.

[6] A nudge, according to Thaler and Sunstein is any form of choice architecture that alters people's behaviour in a predictable way without restricting options or significantly changing their economic incentives.

[10] One of the main justifications for Thaler's and Sunstein's endorsement of libertarian paternalism in Nudge draws on facts of human nature and psychology.

[13] Instances of the Automatic System at work include smiling upon seeing a puppy, getting nervous while experiencing air turbulence, and ducking when a ball is thrown at you.

Sunstein and Thaler state that "the libertarian aspect of our strategies lies in the straightforward insistence that, in general, people should be free to do what they like-and to opt out of undesirable arrangements if they want to do so".

[18] The paternalistic portion of the term "lies in the claim that it is legitimate for choice architects to try to influence people's behavior in order to make their lives longer, healthier, and better".

[19] Sunstein and Thaler apply the idea of nudges in the context of choice architecture to propose policy recommendations in the spirit of libertarian paternalism.

[25] George Will's review for Newsweek magazine stated that "nudges have the additional virtue of annoying those busybody, nanny-state liberals who, as the saying goes, do not care what people do as long as it is compulsory".

[29] Christopher Shea wrote for The Washington Post that "In the end, it must be said, the profusion of proposals in Nudge, however worthy, and the countless summaries of studies supporting them grow a bit wearisome.

As influential as the book is likely to be, it's hard to imagine it pushing its way alongside Malcolm Gladwell's Blink (inferior social science, far breezier style) on the bestseller list".

[30] Elizabeth Kolbert writing for The New Yorker held reservations about some of the book's conclusions when she wrote that many of the suggestions in Nudge seem like good ideas, and even, as with “Save More Tomorrow,” practical ones.

[31]In July 2011, a subgroup of the UK House of Lords Science and Technology Committee concluded a year-long review of behavioral change based on 148 written submissions and evidence from 70 witnesses.

[32]American law professor Pierre Schlag notes that, for all their attention to framing issues, Sunstein and Thaler neglect a number of important questions: "(1) What to optimize?