31 Dunbar’s Theory of Social Circles
Dunbar’s Theory of Circles or The Social Brain Hypothesis, proposes that the size and structure of an individual’s social network are constrained by cognitive limits, specifically the size of the human neocortex. This theory suggests that human ego-networks are organized into distinct layers or circles of intimacy, with each layer representing a different level of social closeness and demanding varying amounts of cognitive and emotional investment, as well as time and energy.
31.1 Core tenets of Dunbar’s Theory
31.1.2 Layered Structure of Ego Networks (Dunbar Circles)
Ego networks, which are centered around an individual (ego) and their contacts (alters), are organized into concentric layers based on intimacy and closeness. Closer layers are smaller and more intimate, while farther layers are larger and less intimate. These different relationships incur varying “maintenance costs” in terms of cognitive, emotional, time, and energy investment. These costs help determine the number of persons in each layer.
The specific layers and their approximate sizes are:
- Support Clique (~4-5 people): This is the innermost and most intimate layer, consisting of an individual’s most intimate kin and best friends. These are the people one can rely on in times of crisis and emergencies. This aligns with Dunbar’s model which suggests a core group of about 5 individuals.
- Sympathy Group (~12-15 people): This layer includes kin and good friends with whom an individual interacts often and who can provide some services. This layer is less intimate than the support clique but still involves frequent interaction.
- Affinity Group (~45-50 people): This group consists of more casual but still close friends and extended family.
- Active Network (~120-150 people): This outermost layer includes the total number of people an individual recognizes by face/name (without help from computers and social media websites) and interacts with at least once a year. This is the largest circle of the Dunbar Circles, representing people an ego considers when making decisions, but does not engage with as frequently.
31.1.3 Tie Strength and Network Layers
Tie strength is a crucial element that correlates with these layers. Strong ties are typically found in the inner, more intimate circles (e.g., support clique and sympathy group), while weak ties are characteristic of the outer layers (e.g., active network). The theory of g-transitivity (Granovetter’s transitivity rule) is more likely to apply to strong ties in the support clique and sympathy group.
31.1.4 Personality Traits and Network Structure
Individual personality traits can influence the structure of one’s ego network within the Dunbar Circles:
- Extraversion/Introversion: People high in extraversion tend to have larger networks across all layers, are more likely to be part of strong tie triads, and are more prone to introduce friends of friends. They also add new contacts at a faster rate and exhibit higher in-degree and out-degree centrality.
- Neuroticism: Individuals high in neuroticism tend to have smaller ego-networks, be part of weak tie triads, and are less likely to introduce friends of friends.
- Agreeableness: People high in agreeableness tend to have higher in-degree centrality and add new contacts at a faster rate.
31.1.1 Social Brain Hypothesis
The fundamental premise is that the relatively large size of the human brain, particularly the neocortex, evolved to manage complex social relationships. The size of the neocortex correlates with average group size across primates, suggesting a cognitive limit to the number of stable relationships an individual can maintain. The brain is essentially for keeping track of other people, among other things.