Lark (person)

A lark, early bird, morning person, or (in Scandinavian countries) an A-person, is a person who usually gets up early in the morning and goes to bed early in the evening. The term relates to the birds known as larks, which are known to sing before dawn. Human "larks" may sleep from around 10 p.m. to 6 a.m. (or earlier), and tend to feel most energetic just after they get up in the morning. They are thus well-suited for working the day shift. The opposite of the lark is the owl, often awake at night. A person called a night owl is someone who usually stays up late and may feel most awake in the evening and at night. Researchers have traditionally used the terms morningness and eveningness to describe these two chronotypes. Till Roenneberg, a chronobiologist in Munich, has mapped the circadian rhythms of more than 200,000 people. Biological processes, including sleep-wake patterns, that display an oscillation of about 24 hours are called circadian rhythms. According to Roenneberg, the distribution of circadian rhythms spans from the very early to the very late chronotypes, similarly to how height varies from short to tall. As circadian rhythm is independent of the number of hours of sleep a person needs, Roenneberg calculates the rhythm based on the midpoint of the sleep period. A person who goes to bed at midnight and rises at 8 thus has the same chronotype as a person who goes to bed at 1 a.m. and rises at 7; the midpoint of sleep is 4 a.m. for both of these individuals. People with early chronotypes will usually not be able to "sleep in", even if they have stayed up later than usual. While fit for a "lark-like" societal framework, they find it hard to adapt to a context where "sleeping in" is common: despite feeling refreshed in the morning, they may feel hampered socially when confronted with some kinds of social gatherings (such as soirées) that are often scheduled for the evening, even if most kinds of social events are not. People with late chronotypes go to bed late and rise late.