Are you an ‘early bird’ or a ‘night owl’?

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Harvard researchers working at Brigham and Women’s Hospital have found that whether someone is a morning person or an evening person depends on a basic aspect of the circadian timing system that is known as intrinsic period. The study was published in the August 2001 issue of “Behavioral Neuroscience. “While some have argued that extremes in sleep-wake timing are personality characteristics, this study reveals that there is a biological basis for morning or evening patterns,” said Charles A. Czeisler, senior author of the study, chief of division at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School. “In this study, we found that differences in a fundamental property of the circadian timing system, its intrinsic period, will determine whether someone is a ‘early bird’ who awakes before dawn or a ‘night owl’ who tends to stay up at night but sleeps in late.” The study was funded by the National Institute on Aging, Air Force Office of Scientific Research, and National Institutes of Health Division of Research Resources.