The lottery is a popular form of gambling. Unlike other forms of gambling, lotteries do not require players to wager money in order to win; winners are chosen at random. In the United States, state governments have monopolies on the operation of lotteries. Typically, profits are earmarked for education or public works projects. Lotteries are widespread, with more than 60% of Americans saying that they play at least once a year. They are also a significant source of political funds, with state politicians often receiving heavy contributions from lottery suppliers in return for support of the industry.

Despite the ubiquity of lotteries, they remain controversial. Critics point to evidence that lotteries promote addictive gambling behavior, impose a major regressive tax on lower-income groups, and lead to illegal gambling. They argue that state governments have a conflict of interest between their desire to raise revenue and their duty to protect the welfare of their citizens.

Leaf Van Boven, a professor of psychology and neuroscience at the University of Colorado Boulder, has studied the psychological motivations that drive people to play the lottery. He says that a major factor is the tendency to overestimate the odds of winning. In addition, he says that people tend to “overweight” small probabilities—if a chance has only a 1% chance of happening, people will treat it as though it has a 5% probability. This is known as the decision weight effect. Lastly, Van Boven says that people also think counterfactual thoughts after making a decision, imagining what would have happened had they done things differently.