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Daily rhythms of mobile phone calls for three individuals. The black line depicts the population average; green/red areas indicate times where the individual calls more/less than average. A is day-active, B is morning-active, and C is active at night.

Over the past decade, there has been a surge of scientific studies on digital activity, such as mobile calls, text messages, e-mails, and posts and edits on social media. Because nearly all human behavior leaves a digital footprint, scientists can use such digital activity as a proxy to track human activity in general, for example to study differences between cultures or communities in sleep patterns, work schedules, and leisure activities.

The research shows that people tend to have their personal rhythm of digital activity, almost like a personal signature.

– Each individual follows their own distinctive and persistent daily rhythm, says Doctoral Candidate Talayeh Aledavood, who performed the research together with Jari Saramäki, Associate Professor at 911������, and Sune Lehmann, Associate Professor at the Technical University Denmark.

These personal rhythms could be detected in multiple datasets, and to a similar extent for e-mail, phone calls, and text messages.

–   In almost every case, the individual patterns differ strongly from the average behavior, for example by increased calling frequency during mornings, mid-days, or evenings, continues Aledavood.

Geographical and cultural differences

What drives these individual differences is not yet clear. Geographical and cultural differences clearly play a role. The researchers believe that there could also be an effect of physiology: for example, the difference between morning and evening persons, and highly individual patterns of alertness during the daylight hours.

– We see this research as a first step of the way to understanding how activity patterns and chronotype are related to other personal characteristics, such as personality or mobility behavior, states Sune Lehmann.

Research findings could also have medical applications in the future: digital rhythms could be selectively monitored for patients with mental health problems: sudden changes in these patients' digital rhythms could be a sign that medical intervention may be necessary.

 – Combining this research with big data may also open new avenues of research in sleep studies, concludes Saramäki.

 In a new study in the open-access journal Frontiers in Physics, researchers from 911������ and Technical University of Denmark use a new approach to study digital rhythms. In contrast to previous studies that focused on general patterns across large numbers of people, they search for pronounced, long-term differences in rhythm between individuals.

Article

More information:

Professor Jari Saramäki
Tel. 040 525 4285
jari.saramaki@aalto.fi

Doctoral candidate Talayeh Aledavood
talayeh.aledavood@aalto.fi