Robin I. M. Dunbar's research while affiliated with University of Oxford and other places

Publications (146)

Article
Primates live in stable social groups in which they form differentiated relationships with group members and use a range of communication including facial expressions, vocalizations and gestures. However, how these different types of communication are used to regulate social interactions, and what cognitive skills underpin this communication, is st...
Article
Primate social bonds are described as being especially complex in their nature, and primates have unusually large brains for their body size compared to other mammals. Communication in primates has attracted considerable attention because of the important role it plays in social bonding. It has been proposed that differentiated social relationships...
Article
Characterizing non-human primate social complexity and its cognitive bases has proved challenging. Using principal component analyses, we show that primate social, ecological and reproductive behaviours condense into two components: socioecological complexity (including most social and ecological variables) and reproductive cooperation (comprising...
Article
Full-text available
Intense sociality has been a catalyser for human culture and civilization. Within this context, our relationships at a personal level play a pivotal role in our health and well-being. These relationships are, however, sensitive to the time we invest in them. To understand how and why this should be, we rst outline the evolutionary background in pri...
Article
In anthropoid primates, social grooming is the principal mechanism (mediated by the central nervous system endorphin system) that underpins social bonding. However, the time available for social grooming is limited, and this imposes an upper limit on the size of group that can be bonded in this way. I suggest that, when hominins needed to increase...
Article
Full-text available
Group-living is stressful for all mammals, and these stresses limit the size of their social groups. Humans live in very large groups by mammal standards, so how have they solved this problem? I use homicide rates as an index of within-community stress for humans living in small-scale ethnographic societies, and show that the frequency of homicide...
Preprint
Humans exhibit what appears to be a unique vocal property: octave equivalence whereby adult male voices are, on average, an octave lower in pitch than those of adult females and children. The evolutionary significance of this seems largely to have escaped notice. While sexual selection might explain why male voices are generally lower, it cannot ex...
Article
Full-text available
Assortative mating is a phenomenon in which romantic partners typically resemble each other at a level greater than chance. There is converging evidence that social behaviours are subject to assortative mating, though less is known regarding social cognition. Social functioning requires the ability to identify and understand the mental states of ot...
Article
Full-text available
Explanations for the evolution of social monogamy in mammals typically emphasise one of two possibilities: females are overdispersed (such that males cannot defend access to more than one female at a time) or males provide a service to the female. However, the first claim has never been formally tested. I test it directly at three levels using popu...
Preprint
Full-text available
In contrast to stable relationships, far less is known about the temporal evolution of transient relationships, although these constitute a substantial fraction of people's communication networks. Previous literature suggests that ratings of relationship emotional intensity decay gradually until the relationship ends. Using mobile phone data from t...
Article
Full-text available
The claim that nonverbal cues provide more information than the linguistic content of a conversational exchange (the Mehrabian Conjecture) has been widely cited and equally widely disputed, mainly on methodological grounds. Most studies that have tested the Conjecture have used individual words or short phrases spoken by actors imitating emotions....
Article
Full-text available
Professional religious specialists centralised religious authority in early human societies and represented some of the earliest instances of formalised social leadership. These individuals played a central role in the emergence of organised religion and transitions to more stratified human societies. Evolutionary theories highlight a range of envi...
Preprint
The capacity to inhibit prepotent actions (self-control) plays a potentially important role in many aspects of the behaviour of birds and mammals. A number of studies, for example, have used it as an index of foraging skills. Inhibition is, however, also crucial for maintaining the temporal and spatial coherence of bonded social groups. Using compa...
Article
Full-text available
Fictional storytelling has played an important role in human cultural life since earliest times, and we are willing to invest significant quantities of time, mental effort and money in it. Nonetheless, the psychological mechanisms that make this possible, and how they relate to the mechanisms that underpin real-world social relationships, remain un...
Article
Full-text available
Mammal social groups vary considerably in size from single individuals to very large herds. In some taxa, these groups are extremely stable, with at least some individuals being members of the same group throughout their lives; in other taxa, groups are unstable, with membership changing by the day. We argue that this variability in grouping patter...
Article
Full-text available
Humans deploy a number of specific behaviours for forming social bonds, one of which is laughter. However, two questions have not yet been investigated with respect to laughter: (1) Does laughter increase the sense of bonding to those with whom we laugh? and (2) Does laughter facilitate prosocial generosity? Using changes in pain threshold as a pro...
Preprint
Full-text available
Assortative mating (AM) is a phenomenon in which romantic partners typically resemble each other at a level greater than chance. There is converging evidence that social behaviours are subject to AM, though less is known regarding social cognition. Social functioning requires the ability to identify and understand the mental states of others, i.e.,...
Article
Full-text available
The C-tactile (CLTM) peripheral nervous system is involved in social bonding in primates and humans through its capacity to trigger the brain’s endorphin system. Since the mammalian cochlea has an unusually high density of similar neurons (type-II spiral ganglion neurons, SGNs), we hypothesise that their function may have been exploited for social...
Article
Full-text available
In species that live in stable groups, successful management of time budget (i.e., the proportion of time involved in different behaviours) and social relationships has been proposed to be a key variable affecting individual fitness. Such management is limited by time constraints, which are group size and season dependancy. However, the link betwee...
Article
Full-text available
We aimed to test the hypothesis that quantitative traits associated with autism spectrum conditions are subject to assortative mating. Study 1 examined self-reported autistic traits (Autism Spectrum Quotient [AQ]), systemizing (Systemizing Quotient-Revised [SQ-R]) and empathizing (Empathy Quotient [EQ]), as well as behavioral measures related to so...
Article
Full-text available
Compared to most other mammals and birds, anthropoid primates have unusually complex societies characterised by bonded social groups. Among primates, this effect is encapsulated in the social brain hypothesis: the robust correlation between various indices of social complexity (social group size, grooming clique size, tactical behaviour, coalition...
Article
Full-text available
Introduction: Previous studies have shown that engaging in formal social participation may protect against declining mental health, but social network size (the number of close social ties a person has) may moderate the relationship. We assessed the potential moderating role of social network size using longitudinal data. Methods: Nationally repr...
Article
Full-text available
Religious rituals are associated with health benefits, potentially produced via social bonding. It is unknown whether secular rituals similarly increase social bonding. We conducted a field study with individuals who celebrate secular rituals at Sunday Assemblies and compared them with participants attending Christian rituals. We assessed levels of...
Preprint
Full-text available
Explanations for the evolution of monogamy in mammals typically emphasise one of two possibilities: monogamy evolves when females are overdispersed (such that males cannot defend more than one female at a time) or when males provide a service to the female. However, the first claim has never been directly tested. I test it directly at three levels...
Article
Full-text available
Humans survive and thrive through social exchange. Yet, social dependency also comes at a cost. Perceived social isolation, or loneliness, affects physical and mental health, cognitive performance, overall life expectancy, and increases vulnerability to Alzheimer's disease-related dementias. Despite severe consequences on behavior and health, the n...
Preprint
Full-text available
Network science and data analytics are used to quantify static and dynamic structures in George R.R. Martin's epic novels, A Song of Ice and Fire, works noted for their scale and complexity. By tracking the network of character interactions as the story unfolds, it is found that structural properties remain approximately stable and comparable to re...
Article
Full-text available
Significance We use mathematical and statistical methods to probe how a sprawling, dynamic, complex narrative of massive scale achieved broad accessibility and acclaim without surrendering to the need for reductionist simplifications. Subtle narrational tricks such as how natural social networks are mirrored and how significant events are scheduled...
Article
Full-text available
Religious rituals are universal human practices that play a seminal role in community bonding. In two experiments, we tested the role of mu-opioids as the active factor fostering social bonding. We used a mu-opioid blocker (naltrexone) in two double-blind studies of rituals from different religious traditions. We found the same effect across both s...
Article
Full-text available
Objective This article addresses the connection between loneliness and physical contact. Evolutionary and psychological research has shown that touch is an important part of bond-building and emotion communication; loneliness is intimately related to these elements as well. In this paper, we ask whether physical contact reduces feelings of loneline...
Article
This study investigated the effects of being mimicked on automatic imitation indices and social cohesion. 180 female participants were either interactively mimicked or anti-mimicked. In the mimicry condition, a confederate topographically aligned, during anti-mimicry, misaligned, their behavior to the participants. Being mimicked may evoke a sense...
Article
Full-text available
Theories differ over whether religious and secular worldviews are in competition or represent overlapping and compatible frameworks. Here we test these theories by examining homogeneity and overlap in Christian and non-religious people's explanations of the world. Christian and non-religious participants produced free text explanations of 54 natura...
Article
Full-text available
The human social world is orders of magnitude smaller than our highly urbanized world might lead us to suppose. In addition, human social networks have a very distinct fractal structure similar to that observed in other primates. In part, this reflects a cognitive constraint, and in part a time constraint, on the capacity for interaction. Structure...
Article
Full-text available
Significance Dunbar hypothesized, on the basis of empirical evidence, that a typical individual can have a stable relation with at most 150 other people. We establish that this number results from the internal dynamics of a complex network. Two network models having phase transitions are used to determine the optimal size for the most efficient inf...
Preprint
Religious rituals are associated with health benefits, potentially produced via social bonding. It is unknown whether secular rituals similarly increase social bonding. We conducted a field study with individuals who celebrate secular rituals at Sunday Assemblies and compared them with participants attending Christian rituals. We assessed levels of...
Article
Full-text available
Topological indices describe mathematical invariants of molecules in mathematical chemistry. M-polynomials of chemical graph theory have freedom about the nature of molecular graphs and they play a role as another topological invariant. Social networks can be both cyclic and acyclic in nature. We develop a novel application of M-polynomials, the (...
Article
Never before have we experienced social isolation on such a massive scale as we have in response to COVID-19. Yet we know that the social environment has a dramatic impact on our sense of life satisfaction and well-being. In times of distress, crisis, or disaster, human resilience depends on the richness and strength of social connections, as well...
Article
Host-associated microbiomes play an increasingly appreciated role in animal metabolism, immunity and health. The microbes in turn depend on their host for resources and can be transmitted across the host’s social network. In this Perspective, we describe how animal social interactions and networks may provide channels for microbial transmission. We...
Article
Full-text available
Microbes colonise all multicellular life, and the gut microbiome has been shown to influence a range of host physiological and behavioural phenotypes. One of the most intriguing and least understood of these influences lies in the domain of the microbiome's interactions with host social behaviour, with new evidence revealing that the gut microbiome...
Preprint
Full-text available
Religious rituals are universal human practices, generally practiced in groups. Social scientists have highlighted for over 100 years its role in bonding individuals, but the mechanisms underlying this function have yet to be explored. Here we tested the role of mu-opioids in fostering social bonding in rituals across two double-blind studies. For...
Preprint
Full-text available
The ‘brain-opioid theory of social attachment’ (BOTSA) has been proposed as providing the neurobiological underpinnings of social bonding. Endorphins are activated in the brain by a variety of social activities, including social touch, laughter, singing, dancing and feasting. Several of these seem to be involved in the processes of bonding whole co...
Article
Full-text available
There is accumulating evidence that being an active member of a social community predicts health, wellbeing and even survival. I use data from an online survey to determine whether religious behavior has the same effect. The results suggest that religiosity and attendance at religious services most strongly affect engagement with the local communit...
Article
Full-text available
In human and nonhuman primates, sex differences typically explain much interindividual variability. Male and female behaviors may have played unique roles in the likely coevolution of increasing brain volume and more complex social dynamics. To explore possible divergence in social brain morphology between men and women living in different social e...
Article
Full-text available
The American National Institute for Mental Health (NIMH) has put out a set of research goals that include a long-term plan to identify more reliable endogenous explanations for a wide variety of mental health disorders (Insel, 2013). In response to this, we have identified a major symptom that underlies multiple mental health disorders – social bon...
Article
Gorillas and chimpanzees live in social groups of very different size and structure. Here I test the hypothesis that this difference might reflect the way fertility maps onto group demography as it does in other Catarrhines. For both genera, birth rates and the number of surviving offspring per female are quadratic (or ∩-shaped) functions of the nu...
Preprint
Full-text available
The American National Institute for Mental Health (NIMH) has put out a set of research goals that include a long-term plan to identify more reliable endogenous explanations for a wide variety of mental health disorders (Insel, 2013). In response to this, we have identified a major symptom that underlies multiple mental health disorders – social bon...
Article
Full-text available
Many species use touching for reinforcing social structures, and particularly, non-human primates use social grooming for managing their social networks. However, it is still unclear how social touch contributes to the maintenance and reinforcement of human social networks. Human studies in Western cultures suggest that the body locations where tou...
Article
The distribution of group sizes in woodland baboons forms a pair of demographic oscillators that trade fertility off against predation risk. Fertility rates, however, set an upper limit on group size of around 90–95 animals. Despite this, two species of baboons (hamadryas and gelada) have groups that significantly exceed this limit, suggesting that...
Article
Full-text available
To understand how species will respond to environmental changes, it is important to know how those changes will affect the ecological stress that animals experience. Time constraints can be used as indicators of ecological stress. Here we test whether time constraints can help us understand group sizes, distribution patterns, and community sizes of...
Article
Full-text available
The typical human personal social network contains about 150 relationships including kin, friends, and acquaintances, organized into a set of hierarchically inclusive layers of increasing size but decreasing emotional intensity. Data from a number of different sources reveal that these inclusive layers exhibit a constant scaling ratio of [Formula:...
Article
Full-text available
Exploitation of food resources that are dispersed in time and space has been crucial to the evolutionary success of humans. Recent experimental work has shown that an absence of communication impairs decision‐making in a foraging task. Here, we found that individuals in larger teams were more likely to reach group consensus and were more accurate a...
Preprint
Full-text available
It has been suggested that monogamy evolves when females forage alone and are overdispersed, such that males cannot defend more than one female at a time. I test the underlying assumption that the females of monogamous anthropoid primates are overdispersed in three different ways, and compare the results with data for several polygynous primate gen...
Preprint
Full-text available
Cluster analysis reveals a fractal pattern in the sizes of baboon groups, with peaks at ~20, ~40, ~80 and ~160. Although all baboon species individually exhibit this pattern, the two largest are mainly characteristic of the hamadryas and gelada. We suggest that these constitute three pairs of linear oscillators (20/40, 40/80 and 80/160), where in e...
Article
Full-text available
The reading of fiction has been found to confer benefits, including increased empathy and understanding of others. Among ongoing research questions are those of how people engage in imagined worlds while keeping in touch with the currently perceived world, as well as how far stories were important in human evolution and how the brain is involved un...
Article
Psychology and microbiology make unlikely friends, but the past decade has witnessed striking bidirectional associations between intrinsic gut microbes and the brain, relationships with largely untested psychological implications. Although microbe-brain relationships are receiving a great deal of attention in biomedicine and neuroscience, psycholog...
Article
Full-text available
We investigated associations between online and offline socialising and groups of social ties as postulated by the Social Brain Hypothesis (SBH). An online survey of social media use, social satisfaction and loneliness generated 249 complete responses from a sample of staff and students at the University of Manchester. Regression-based analyses sho...
Article
Full-text available
Social skills rely on a specific set of cognitive processes, raising the possibility that individual differences in social networks are related to differences in specific brain structural and functional networks. Here, we tested this hypothesis with multimodality neuroimaging. With diffusion MRI (DMRI), we showed that differences in structural inte...
Article
Full-text available
In mammals, and especially primates, group size and social complexity are typically correlated. However, we have no general explanation why this is so. I suggest that the answer may lie in one of the costs of group living: mammalian reproductive endocrinology is extremely sensitive to stress, and forms one of the hidden costs of living in groups. F...
Article
Transportation, the experience of feeling “transported” into a fictional world, differs widely across individuals. We examined transportation in 3 studies. Study 1 investigated links between individual differences in various measures of audience response, whereas the latter 2 studies examined links between trait measures (independent variables) and...
Article
Friendship is the single most important factor influencing our health, well-being, and happiness. Creating and maintaining friendships is, however, extremely costly, in terms of both the time that has to be invested and the cognitive mechanisms that underpin them. Nonetheless, personal social networks exhibit many constancies, notably in their size...
Article
Full-text available
Primate groups vary considerably in size across species. Nonetheless, the distribution of mean species group size has a regular scaling pattern with preferred sizes approximating 2.5, 5, 15, 30 and 50 individuals (although strepsirrhines lack the latter two), with a scaling ratio of approximately 2.5 similar to that observed in human social network...