- The body’s natural 24-hour cycle,
- roughly matched to the day/night cycle of light and dark.
- the 24 hour cycle, the following factors vary, rising and falling over the
- course of the day and night:
- Daily rhythms vary from person to person
- and with age.
General peaks in alertness:
§evening peak—20-year old “owls”
§morning peak—50-year old “larks”