Natasha Dow Schüll in the Casino (p.217):

The gambling industry invests a great deal of resources and creative energy into the project of helping gamblers to ‘lose’ themselves — experientially and financially. Slot designers’ goal is to build machines that can extract maximum ‘revenue per available customer’, or revpac, and of this all-consuming objective they talk freely and explicitly among themselves — on conference panels, in journals, and in the aisles and meeting lounges of exposition floors. How to get people to gamble longer, faster, and more intensively? How to turn casual players into repeat players? How, in other words, to design the zone?