Subjects are presented with gambles in which they have a 50% chance of gaining some amount of money and a 50% chance of losing some other amount of money. The subject decides whether or not they would accept the gamble. The amount of the potential gain and loss are varied across trials. Gambles are not resolved during performance of the task; after the end of the task, some gambles are chosen at random and played for real money if they were accepted.
Definition contributed by MLewis about a week ago.