An interesting bump in the curve of human sleep-wake cycle sometimes appears--a period of daytime sleep called a nap. Although napping habits vary across cultures, research shows that napping is a common feature of healthy adult sleep-wake behavior, even when no sleep debt was incurred the night before the nap[9]. So why don't we all require naps? Apparently, napping can be easily suppressed (such as when one is at work) because naps "tend to occur as transient events in an otherwise rising circadian function of behavioral and physiological activation"[9]. In 1994, Aschoff discovered that neither the duration of the main sleep nor the circadian cycle is affected by napping[10].