Mice don’t own alarm clocks – so how do they know when it’s time to wake up? Mice are nocturnal which means they are most active at night. Something inside of them causes them to wake up in the evening and go about their business. This behavior is probably useful since the darkness hides them from predators.
Similarly, owls do not get up with the sunrise, but rather hunt at night when some unlucky mouse is likely to become their dinner. It’s clear that the ability of these creatures to match up their behavior with nature’s rhythms (like the day and night cycle) is critical for their survival.
The activity patterns of mice and owls are examples of biological rhythms that are synchronized to the day/night cycle. These patterns are called circadian rhythms. This phrase has Latin roots. Circa means “about” and dian means “a day.” A circadian rhythm cycles over a one day period.
Other biological rhythms are tied to the tides or the season which are much longer (from hours to months). Circadian rhythms are important because they influence so many aspects of our daily lives. These rhythms influence everything from when we get tired, to when we feel at our best, to when we are hungry.
Biological Rhythms
People function on a variety of time cycles. We have seasons of the year, days of the week, and hours of the day. Psychologists are interested in the degree to which we are influenced by our external environment versus internal biological rhythms, or periodic changes in physiological functioning. One biological rhythm is the circadian cycle (from the Latin words, "about a day"). Our bodies appear to be genetically programmed to function on roughly a 24-hour cycle. An early test of this concept was carried out by sleep researchers Nathaniel Kleitman and B.
