This paper introduced homophily based friendship choice into a model in which individuals replace missing kin with non-kin friends. The results show that similarity-based friendship choice increases the clustering coefficient, and thus it is an adaptive response to decreasing interconnectedness within the individual’s immediate social network. This is of import as although the clustering coefficient may fall for a number of reasons for any one individual, for an entire society it tends to be associated with demographic processes in which the number of available relatives falls34. Urbanisation, falling fertility, migration, war, and epidemics can all result in reduced access to kin, either because relatives are not available, as in urbanisation and migration, or they were never born, as in falling fertility, or have died in wars and epidemics. The consequence of all these demographic processes is a fall in the clustering coefficient that results in increasing incentives for norm violation and evaporating social trust34.
Homophily is adaptive behaviour in increasing the clustering coefficient
It has been suggested in the previous literature that the implementation of law, i.e., an institutionalised third party punishment system is a society-level response to increased norm violations34. This paper has shown that homophilic friendship choice can be seen as a parallel, individual-level response. When traditional kin networks break up, the average clustering coefficient falls34, which people perceive as feeling lonely, disconnected, surrounded by a social environment in which trust collapses, and norm violating behaviours become frequent41,42,43. To reverse the fall in the clustering coefficient, the individuals’ optimal response is to rely on a friendship choice strategy based on trait similarity. Notice, however, this individually adaptive behaviour may not be a societally optimal response if as a consequence a network cleavage emerges.
Social identity is a consequence of homophily
The social network literature, which does not have an evolutionary behavioural science-based approach, suggested a causal link from identity to social network homophily44: people are raised with socially constructed identities which determine the traits in which people choose each other as social connections. This paper’s logic suggests causality in the opposite direction: first, people agree on the traits on which similarity-based friendship choice can take place. The content of these traits is irrelevant, as long as there is a societal consensus concerning the traits themselves. Using these traits, people build their social networks using trait similarity as a friendship choice heuristic. The consequently high network clustering leads to dense subgroups emerging. The social identity of individuals within such subgroups may then be merely a mental shorthand.
The logic of falling clustering to homophilic friendship choice to segmentation to group identity would explain why the phenomenon of trait-based societal segmentation has emerged historically with urbanisation and falling fertility, and why there is such a wide range of traits along which social identities emerge, despite the similarity of many societal and economic factors in the underlying societies.
Transition clique-iness
The results suggest a clustering coefficient pattern during demographic processes in a u-shaped curve, predicting that mid-transition societies are particularly prone to a crisis of trust and norm-violation. If this is true, then societies in the middle of demographic change are more likely to exhibit coping behaviours. Shifting from predominantly rural to urban living, a large influx of migration, prolonged war, or deadly epidemics should increase the importance of sub-group membership (e.g., clubs), group signalling behaviours (e.g., special handshakes), and difficult-to-fake markers of origins (e.g., accents). Through the middle of the u-shaped curve, clique-iness becomes normal behaviour, which may fade away once the transition is over if replaced by multi-dimensional trait signalling.
Fake news
Notice that although the clustering coefficient of a homophily-based friendship network can be as high as for a traditional kin-based one, there remains a crucial difference. While the stability of network edges is high among relatives as these tend to be fixed for life, friendship edges are less certain. Empirically, it has been established that without maintenance via meaningful social interactions, friendship wanes faster than kinship does15. Friends, in general, are not chosen for life, these relationships need to be reaffirmed with regularity. To be chosen and re-chosen by their friends, people need to keep signalling their type. This might be particularly pertinent in societies in which others with whom there is a similarity in a number of traits are much more numerous than the personal sociality limit.
In these societies, individuals might feel a need to signal their traits frequently, and in a way that stands out as new. Seasonally changing fashion associated with brands, and competition news about affiliated sport clubs may serve as a source of such flow of markers. Anecdotal observation suggests that it is customary in many societies to start social interaction with a “banter” that refers to news concerning one’s chosen brand (car, clothing, accessory, food etc.) or club (sport, religion, political party etc.) affiliation.
In the past decade, with the rise of social networking apps, a new pathway has opened up for this similarity marker reaffirmation: internet-based news outlets provide a constant flow of possible markers, while social networking apps provide a way of renewing self-assignment to type, by passing on, or “wearing”, the ever newer signals of affiliation. Thus, the fake news phenomenon can be viewed as a side effect of an individual-level coping mechanism responding to decreasing clustering coefficient due to urbanisation, falling fertility, migration, exploited by politically motivated institutions.
In summary, this paper offers a theoretical argument that shows how homophily, i.e., using trait similarity as a friend selection criterion, can increase the clustering coefficient of the social network. Thus, if, as argued in previous literature, higher local connectedness is beneficial for the individual by increasing the cooperative stance of the network partners, achieving this aim using homophily is an adaptive behaviour. Furthermore, the results also suggest that societies that go from a rural, high fertility, low migration state to an urban, low fertility, high migration state are likely to go through a u-shaped transition period in terms of clustering coefficient. If the lower clustering coefficients are associated with increasing norm violations, this theoretical result offers a new explanation for the transition crises in countries that have gone through this shift in recent history.
Source: Ecology - nature.com
