Statistical properties of human activity and criticality in active behavior

¹ Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University Seoul 08826, Korea
² Institute for Theoretical Physics II: Soft Matter, Heinrich- Heine University Düsseldorf D-40225 Düsseldorf, Germany
³ Department of Healthcare Information Technology, Inje University - Gimhae 50834, Korea
⁴ Department of Psychiatry and Center for Sleep and Chronobiology, Seoul National University College of Medicine and Hospital - Seoul 03080, Korea
⁵ Department of Psychiatry, Sungkyunkwan University College of Medicine, Samsung Medical Center Seoul 06351, Korea

^(a) jongwonkim@inje.ac.kr
^(b) mychoi@snu.ac.kr

Received: 12 March 2019
Accepted: 17 June 2019

Abstract

We study the statistical properties of human activities by analyzing actigraphy data that monitor wrist movements of normal subjects and patients with bipolar II disorder. Probing the distribution of sizes, lifetimes, and quiet times for active bouts, we identify power-law behavior and detect a significant difference between the two groups in the scaling exponent of the quiet-time distribution. Scale invariance in active bouts is further examined through the dynamical exponent and scale transformation while temporal correlations of the activities are explored by means of the detrended fluctuation analysis. In both normal subjects and patients, long-time correlations are apparent in wake periods which bear most active bouts. These correlations are, albeit relatively weak, related to the amount of active bouts during sleep. Our findings suggest that human movements in daily life are regulated to (near-)criticality.