Behavioral economics studies how psychology affects economic decisions, and how people's choices often deviate from what traditional theory predicts. Classic models assume people are rational and weigh every option carefully, but real people are influenced by biases, habits, emotions and social pressure. Its foundations were laid in the last three decades of the 20th century, though its roots go back to Adam Smith's observations on how desires shape behaviour. Its models usually combine psychology, neuroscience and microeconomics.

In 1909 D. W. Griffith made a 14-minute film about a speculator who corners the wheat market and doubles the price of bread. A farmer sows his field while a 'Wheat King' gambles in the Chicago wheat pit; bakers raise the loaf from five cents to ten and the poor line up for bread. Griffith cut back and forth between the farm, the feast and the breadline, a technique called parallel editing, so audiences saw both ends of the economy at once. The film drew on Frank Norris's stories and on a real scheme: months earlier Chicago financier James Patten had cornered wheat, sent bread prices up and made about $5 million, roughly $185 million today.