11.   Stay away from caffeinated beverages, and large amounts of alcohol, since both will interfere with natural sleep cycles.

12.   Some are bleary-eyed, some have the quick stride of a person who has managed to reverse his sleep cycle and trade night for day.

13.   They do this because their sleep cycles are like that.

14.   Your sleep recording will also reveal the pattern of your sleep cycles and the total amount of time you spend in each stage.

15.   Siffre tells researchers what day he thinks it is so they can study his sleep cycles and his notion of time.