Inferring circadian rhythms of cognitive performance in everyday life

Physical, mental, and behavioral processes of most living beings underlie cyclic changes, mainly governed by the day-night cycle. Investigations of these circadian rhythms have traditionally required constrained settings and invasive methods, such as repetitive blood testing and testing in sleep laboratories. Recent developments in pervasive technology, e.g., the proliferation of smartphones in our everyday lives, allow us to develop less intrusive ways to infer circadian rhythmicity in everyday settings. In this article, we present an overview of the current state of research, describe a mobile toolkit for collecting ground truth data on cognitive state fluctuations, and detail the implementation of a wearable system to unobtrusively detect alertness changes in the wild. Understanding and monitoring circadian rhythms will lead to the development of interventions to support mental health, physical health, and will ease the negative consequences of time shifts inflicted by jet lag or shift-work.