Final Report Summary - RELNET (Psychology of Relationships, Networks and Community Cohesion) This project aimed to explore the mechanisms that underlie social relationships and, by extension, community cohesion. It adopted a multidisciplinary approach that integrated a number of very different disciplinary approaches, including experimental psychology, neuroscience, computational modelling, linguistics, history, anthropology, sociology, evolutionary biology, and literary studies. We showed that kinship (family relationships) are an important factor mediating our relationships, and that this is underpinned by different neural mechanisms in the brain than friendships in such a way as to allow kinship relationships to be processed faster than friend relationships. We showed that a number of social activities, including laughter, singing, dancing, storytelling, feasting and drinking all enhance a sense of belonging to a community by triggering the endorphin system in the brain. We showed this both through behavioural experiments and through brain scanning. We also undertook a very largescale study of the genetics of the social neurochemicals, and showed that ocytocin (widely touted as the social neurohormone) is in fact limited to romantic relationships, and that the endorphin and dopamine systems (working in close tandem) are the important mechanisms at all levels of sociality. We undertook a number of studies on community formation and structure, both in real life with real communities and in the digital world through experimental designs using mock social networking sites. Extensive analyses of real world communities, including telephone networks, Facebook and Twitter communities, and German residential campsites, as well as historical communities, revealed that not only does the number 150 (‘Dunbar’s Number’) typify these, but these communities are structured in a very particular way into layers with a fractal pattern in which each layer is three times the size of the one inside it. Not only are the numbers that describe these layers (15, 50, 150, 500 and 1500) unusually common, but they also seem to represent grouping sizes that are particularly stable and longlasting. This finding has important implications for the structure of business and other organisations. Significantly, these numbers also turn up in the grouping patterns of monkeys and apes, suggesting that that mechanisms that give rise to them are very ancient and widespread among the primates as a whole. We used agent based modelling to explore the dynamics of community formation. We showed: that structured networks arise naturally when time and cognitive capacity are limited; that language as a mechanism for bonding large groups evolves slowly, but when it finally arrives does so precipitously; that layered social organisations such as those found in primates and humans are selected for only under a very limited range of environmental conditions, thus explaining why they are rare; and that, while self-interested lying is destructive for social networks, ‘white lies’ are often highly integrative. Put together, these various findings allowed us to develop a novel theoretical framework for understanding social evolution that applies widely across the mammals, and in particular the primates. This involves a two-process mechanism that underpins social relationships (a psychopharmacological mechanism based mainly on the endorphin system and a cognitive system that makes it possible to develop relationships of trust, reciprocity and obligation). We were able to show that the principal problem faced by all primate (and probably mammal) societies is not ecological competition (as we have always assumed) but social competition and the effect this has on female fertility. The evolution of close social relationships in these species is an attempt to minimise this effect in order to allow the animals to live in large social groups. In effect, we are now able to provide a coherent, integrated explanation for social evolution within the mammals as a whole, which at the same time explains why primates (and humans) appear to be so different.
