In microeconomics, consumer surplus represents the economic gain that consumers experience when they purchase a good or service for less than the highest price they are willing to pay. This surplus arises from the characteristics of the demand function, which links the quantity of a good to the price consumers are willing to pay. As the quantity of a good increases, the price that consumers are willing to pay for each additional unit typically decreases, resulting in a downward-sloping demand...

Researchers have tested many persuasion strategies, including the foot-in-the door and the door-in-the-face techniques, in a variety of contexts. Ultimately, the principles are effective in selling products and changing people’s attitude, ideas, and behaviors (Cialdini & Goldstein, 2004).