Figure 2.

Scenarios of sleep regularity. (A) Scenario 0 illustrates a perfectly regular sleep–wake pattern over 28 days (zero variation). (B) Scenario 1 adds daily variation in midsleep, sleep duration, or both. (C) Scenario 1A uses sleep–wake patterns from Scenario 1, but with re-arranged (“scrambled”) order of days. (D) Scenario 2 adds weekly variation to sleep–wake patterns from Scenario 1. Scenarios 3 to 5 further add (E) daytime naps, (F) nocturnal awakenings, or (G) “all-nighters” (nights with no sleep) to Scenario 2. (H) Scenario 6 uses sleep–wake patterns of Scenario 2, varying the number of days (2–28) to simulate varying study lengths, illustrated by the gradual shading.