title: Daily Rhythms in Mobile Telephone Communication.
abstract: Circadian rhythms are known to be important drivers of human activity and the recent availability of electronic records of human behaviour has provided fine-grained data of temporal patterns of activity on a large scale. Further, questionnaire studies have identified important individual differences in circadian rhythms, with people broadly categorised into morning-like or evening-like individuals. However, little is known about the social aspects of these circadian rhythms, or how they vary across individuals. In this study we use a unique 18-month dataset that combines mobile phone calls and questionnaire data to examine individual differences in the daily rhythms of mobile phone activity. We demonstrate clear individual differences in daily patterns of phone calls, and show that these individual differences are persistent despite a high degree of turnover in the individuals' social networks. Further, women's calls were longer than men's calls, especially during the evening and at night, and these calls were typically focused on a small number of emotionally intense relationships. These results demonstrate that individual differences in circadian rhythms are not just related to broad patterns of morningness and eveningness, but have a strong social component, in directing phone calls to specific individuals at specific times of day.
authors.affiliation: Department of Computer Science, Aalto University School of Science, Espoo, Finland.
authors.forename: Talayeh
authors.initials: T
authors.lastname: Aledavood
authors.affiliation: CABDyN Complexity Center, Saïd Business School, University of Oxford, Oxford, United Kingdom.
authors.forename: Eduardo
authors.initials: E
authors.lastname: López
authors.affiliation: Department of Psychology, University of Chester, Chester, United Kingdom.
authors.forename: Sam G B
authors.initials: SG
authors.lastname: Roberts
authors.affiliation: CABDyN Complexity Center, Saïd Business School, University of Oxford, Oxford, United Kingdom; Department of Sociology, University of Oxford, Oxford, United Kingdom.
authors.forename: Felix
authors.initials: F
authors.lastname: Reed-Tsochas
authors.affiliation: Departamento de Matemáticas & GISC, Universidad Carlos III de Madrid, Leganós, Spain.
authors.forename: Esteban
authors.initials: E
authors.lastname: Moro
authors.affiliation: Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom.
authors.forename: Robin I M
authors.initials: RI
authors.lastname: Dunbar
authors.affiliation: Department of Computer Science, Aalto University School of Science, Espoo, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Saramäki
mesh_terms: D040421:Cell Phone; D002940:Circadian Rhythm; D005260:Female; D033062:Friends; D006801:Humans; D007206:Individuality; D008297:Male; D066252:Sociological Factors; D014705:Verbal Behavior