His laboratory science focuses on neurobehavioral and physiological regulation of human health and behavior by circadian and sleep biology. The primary focus is on identifying the manner in which sleep need and circadian biology interact to influence wakefulness and neurobehavioral, cognitive, affective and physiological functions (immune, inflammatory, endocrine, metabolic, genetic). His laboratory’s scientific methodologies and capabilities include actigraphy, cognitive and neurobehavioral testing, human electrophysiology, endocrine measures, epidemiology, genetics, metabolic measures, neuroimaging, machine vision, and biomathematical modeling. The research aligns with translational studies of sleep and chronobiology in animal models. The research is often collaborative with investigators at Penn and elsewhere. He created and validated the psychomotor vigilance test (PVT), which is among the most widely used assays for behavioral alertness relative to sleep and circadian dynamics biology. His has conducted seminal experiments on the effects of chronic sleep restriction in healthy adults living in a specially-equipped Sleep and Chronobiology Laboratory in the Hospital of the University of Pennsylvania. His laboratory’s current experiments focus on the nature of recovery dynamics from sleep loss; phenotypic differences in vulnerability to the effects of sleep loss; and the development of novel behavioral, physiological and technological ways to detect, manage and mitigate the effects of sleep loss. He and his colleagues also conduct naturalistic and interventional field research on healthy adults living near and/or working in safety-sensitive occupations that induce sleep disturbance, sleep loss, and circadian misalignment (e.g., astronauts, civilian and military pilots, health care professionals, commercial truck drivers, etc.). He has also conducted studies on the International Space Station, and in various space analog environments (Mars 500, NEEMO, HERA). His research findings are often used in public policy areas relative to work hours, prevention and detection of fatigue, and standards for health and safety. He has more than 300 scholarly publications and is a member of Penn’s Center for Sleep and Circadian Neurobiology, the Institute for Translational Medicine and Therapeutics, the Center for Functional Neuroimaging, the Penn Genomics Frontiers Institute, and the Psychology Department Graduate Group. He lectures in the Perelman School of Medicine, and in Biological Basis of Behavior Program in the School of Arts and Sciences. He has an extensive track record of training students (post-baccalaureate, medical students, graduate students and post-doctoral fellows). He has served on an NIH Advisory Council and numerous IOM/NRC committees; been the Editor-in-Chief of SLEEP; president of the World Sleep Federation; on an NIH Advisory Council; president of the Sleep Research Society; and on the Board of Directors of the American Academy of Sleep Medicine and National Sleep Foundation. He is a scientific Team Leader for the National Space Biomedical Research Institute, and an elected member of the International Academy of Astronautics. His scientific work has relevance to public policies, and he has served NRC and IOM committees focused on issues of regulated work hours, sleep need, health and safety. He is the recipient of numerous awards, including the 2001 Senator Mark O. Hatfield Public Policy Award from the American Academy of Sleep Medicine; the 2004 Decade of Behavior Research Award from the American Psychological Association; the 2007 NASA Distinguished Public Service Medal, which is the highest honor NASA awards to a non-Government employee; and the 2009 Raymond F. Longacre Award for Outstanding Accomplishment in the Psychological and Psychiatric Aspects of Aerospace Medicine from the Aerospace Medical Association.