A single B-FIC was composed of men and women who rotated sleeping with all of the opposite-sex members on a balanced rotational sleeping schedule. The sleeping-schedule assigned each family member to sleep with a different opposite-sex partner each night. Since the BFICs were rarely balanced between men and women (typically more women than men), on any given night several family-members would have no partner to sleep with and were assigned a 'Zero-Night' - when they slept alone. In addition to the programmed sleeping schedule, it was permitted to sleep with any opposite-sex family-member at any time, which was termed a 'freebie'.