The study of human behaviour has always been a difficult, time consuming and expensive business. Anthropologists have largely carried out their research with small scale experiments in the lab, field observations and questionnaires.

All this has changed in recent years with the mobile phone revolution. All of a sudden, social scientists have been able to study humanity cheaply and easily on an unprecedented scale. This data has revealed detailed patterns of commuting, rhythms in cities and even ways of measuring economic prosperity.

Today, Talayeh Aledavood at Aalto University in Finland and a few pals take this process to new levels of detail. These guys have combined the old and new approaches by gathering mobile phone data about when and where people contact each other and combining it with the information from questionnaires about the significance of the relationships people have with each other.

The results provide a unique window into human behaviour. They show how daily patterns of communication are remarkably robust to major life changes. It also reveals fascinating detail about the way in which gender influences the resources men and women allocate to communication strategies.

Aledavood and co begin by recruiting 24 individuals who agreed to share their phone data over 18 months as well as to fill out questionnaires about their relationships with all the people they have regular contact with. In return, the researchers covered the cost of their calls throughout the study.

These individuals were all students about to finish high school. So every person underwent a major life change during the study in moving from school to university or work, often in another city. This allowed the researchers to study the effect of this kind of disruption on communication patterns.

The results reveal some interesting insights. First, individuals show clear patterns of behaviour, such as making more calls in the morning compared to the evening. “In terms of call frequency at each hour of day, each individual has their distinct, persistent pattern,” they say.

They also show that the call patterns vary throughout the day. “There are clear variations in the entropy of [people] called, indicating that certain times of day (evening and night, typically) are reserved for calling specific others, whereas at other times the recipients of calls are more diverse,” say Aledavood and co.

There is a strong difference between the genders. For example, among women, there is a much greater variation of call duration, with longer calls more likely to occur in the evening.

What’s more, these long calls are more likely to be directed to a significant other but not a family member. “Our finding speaks to the importance of female choice in human mating strategies – that having made up their mind, women are typically much more focused in pursuing and investing in their relationships, and especially romantic relationships,” conclude Aledavood and co. “The fact that these ”special” calls are reserved for the evening reinforces the suggestion that the hours of darkness have a special quality for certain kinds of social interactions and social relationships.”

A curious feature of male and female calling patterns is that it is much less common to call kin in the evenings. “This would reinforce the claim that relationships with kin are less fragile than those with friends, and hence require less persistent and less special servicing,” they say. Indeed, they find that the quality of friendships deteriorates within months in the absence of sufficiently frequent contact.

These patterns turn out to be remarkably robust to life-changes. Aledavood and co show that most individuals maintain the same pattern of communication when they move from high school to university or work. That strongly suggests that personality characteristics have an important role in communication patterns and the team want to investigate this in more detail in future.

That’s interesting work that provides yet more insight into the nature of human communication and the role it plays in reproductive strategies.

Ref: arxiv.org/abs/1502.06866 : Daily Rhythms In Mobile Telephone Communication