Constancy of our social signatures.

Robin Dunbar and collaborators have done an interesting examination of the persistence of how many close contacts we maintain (family and close friends) over time, even as the identities of those who are close to us changes. Dunbar is the guy who is well known for his early work showing a correlation between the brain size of social mammals and the size of their social groups. His line relating brain size to group size put the maximal or optimal size of human groups at about 150 individuals. (Enter 'Dunbar' in the search box to the left to see several MindBlog posts on his work.) Here are some clips from their article.

...It appears that having strong and supportive relationships, characterized by closeness and emotional intensity, is essential for health and well-being in both humans and other primates. At the same time, there is a higher cost to maintaining closer relationships, reflected in the amount of effort required to maintain a relation at the desired level of emotional closeness. Because of this, the number of emotionally intense relationships is typically small. Moreover, it has been suggested that ego networks, the sets of ties individuals (egos) have to their friends and family (alters), may be subject to more general constraints associated with limits on human abilities to interact with large numbers of alters. Although there are obvious constraints on the time available for interactions, additional constraints may also arise through limits on memory capacity or other cognitive abilities.

..it is reasonable to ask whether such mechanisms shape these networks in similar ways under different circumstances, giving rise to some characteristic features that persist over time despite network turnover...We combine detailed, autorecorded data from mobile phone call records with survey data. These were collected during a study that tracked changes in the ego networks of 24 students over 18 mo as they made the transition from school to university or work. These changes in personal circumstances result in a period of flux for the social relationships of the participants, with many alters both leaving and entering their networks. This provides a unique setting for studying network-level structure and its response to major changes in social circumstances.

Our results establish three unique findings: (i) There is a consistent, broad, and robust pattern in the way people allocate their communication across the members of their social network, with a small number of top-ranked, emotionally close alters receiving a disproportionately large fraction of calls; (ii) within this general pattern, there is clear individual-level variation so that each individual has a characteristic social signature depicting his or her particular way of communication allocation; and (iii) this individual social signature remains stable and retains its characteristic shape over time and is only weakly affected by network turnover. Thus, individuals appear to differ in how they allocate their available time to their alters, irrespective of who these alters are. Further, our subsidiary analyses (SI Text) suggest that this finding applies not just to call frequencies, because the frequency of calls to an alter correlates with emotional closeness and frequency of face-to-face interactions.

Here is their summary abstract:

We combine cell phone data with survey responses to show that a person’s social signature, as we call the pattern of their interactions with different friends and family members, is remarkably robust. People focus a high proportion of their communication efforts on a small number of individuals, and this behavior persists even when there are changes in the identity of the individuals involved. Although social signatures vary between individuals, a given individual appears to retain a specific social signature over time. Our results are likely to reflect limitations in the ability of humans to maintain many emotionally close relationships, both because of limited time and because the emotional “capital” that individuals can allocate between family members and friends is finite.