R.I.M. Dunbar

Although brain size and body size co-evolves in primates, the correlation is far from perfect. This was originally interpreted as implying that evolutionary changes in brain size lag behind evolutionary changes in body size. Subsequent tests of the hypothesis, however, concluded that there is no meaningful lag. I reanalyse the original data taking socio-cognitive grades into account and show that there is, in fact, a very strog lag effect, but that the original catch-up hypothesis is not the explanation. Rather, the lag is part of an adaptive response to predation risk in which species initially respond by increasing body size, but later switch to increasing group size (with the latter made possible by a correlated increase in brain size). This adaptive response takes between 2 and 8 million years to fully implement, and is dependent on a switch to a more energy-rich diet. This trajectory can be clearly documented in the evolutionary history of fossil hominins over the past 5 My.

We use a modeling approach parameterized with current UK lifehistory data to show that, if they are to match the reproductive performance of women in the higher socio-economic classes, women in lower socio-economic classes must opt for a significantly earlier onset of reproduction in order to offset the higher class-specific mortality and infertility rates that they face. Women from low socio-economic classes cannot afford to postpone reproduction in order to enter a career unless that career pathway facilitates upward mobility into a higher socioeconomic class.

Pocket cartoons are a regular feature of most contemporary newspapers and magazines. As such, they represent a way of conveying complex social and political commentary in a simple visual form. How well we enjoy verbal (oral) jokes depends on the number of mindstates in the joke, and here we ask whether this is also true of visual cartoons. We use survey data from a sample of 3,380 participants attending a public exhibition of published print media cartoons by well-known cartoonists to determine the extent to which viewers’ ratings of cartoons are determined by the mentalizing content of cartoons, the participants’ gender and age, and the publication date of the cartoon. We show that the number of mindstates involved in the cartoon affects its appreciation, just as in verbal jokes. In addition, we show that preferred topics vary by age and gender. While both genders strongly prefer cartoons that explore the …

Hybrid working has its benefits, but employees will be happier and more productive with more face-to-face contact, says Robin Dunbar

We present a simple argument using Promise Theory and dimensional analysis for the Dunbar scaling hierarchy, supported by recent data from group formation in Wikipedia editing. We show how the assumption of a common priority seeds group alignment until the costs associated with attending to the group outweigh the benefits in a detailed balance scenario. Subject to partial efficiency of implementing promised intentions, we can reproduce a series of compatible rates that balance growth with entropy.

The rapid shifts of society have brought about changes in human behavioral patterns, with increased evening activities, increased screen time, and postponed sleep schedules. As an explicit manifestation of circadian rhythms, chronotype is closely intertwined with both physical and mental health. Night owls often exhibit more unhealthy lifestyle habits, are more susceptible to mood disorders, and have poorer physical fitness. Although individual differences in chronotype yield varying consequences, their neurobiological underpinnings remain elusive. Here we carry out a pattern-learning analysis, and capitalize on a vast array of~ 1,000 phenome-wide phenotypes with three brain-imaging modalities (region volume of gray matter, whiter-matter fiber tracts, and functional connectivity) in 27,030 UK Biobank participants. The resulting multi-level depicts of brain images converge on the basal ganglia, limbic system, hippocampus, as well as cerebellum vermis, thus implicating key nodes in habit formation, emotional regulation and reward processing. Complementary by comprehensive investigations of in-deep phenotypic collections, our population study offers evidence of behavioral pattern disparities linked to distinct chronotype-related behavioral tendencies in our societies.

Human communities have self-organizing properties that give rise to very specific natural grouping patterns, reflected in the Dunbar Number and its layered structure (a Dunbar Graph). Since work-groups are necessarily also social groups, we might expect the same principles to apply here as well. One factor likely to be important in limiting the size of groups is that conflicts typically escalate with the number of people involved. Here we analyse Wikipedia editing histories across a wide range of topics to show that there is an emergent coherence in the size of groups formed transiently to edit the content of subject texts, with two peaks averaging at around for the size corresponding to maximal contention, and at around as a regular team. These values are consistent with the observed sizes of conversational groups, as well as the hierarchical structuring of Dunbar graphs. We use the Promise Theory of trust to suggest a scaling law that may apply to all group distributions based on seeded attraction. In addition to providing further evidence that even natural communities of strangers are self-organising, the results have important implications for the governance of the Wikipedia commons and for the security of all online social platforms and associations.

Human communities have self-organizing properties in which specific Dunbar Numbers may be invoked to explain group attachments. By analyzing Wikipedia editing histories across a wide range of subject pages, we show that there is an emergent coherence in the size of transient groups formed to edit the content of subject texts, with two peaks averaging at around N= 8 for the size corresponding to maximal contention, and at around N= 4 as a regular team. These values are consistent with the observed sizes of conversational groups, as well as the hierarchical structuring of Dunbar graphs. We use the Promise Theory model of bipartite trust to derive a scaling law that fits the data and may apply to all group size distributions, when based on attraction to a seeded group process. In addition to providing further evidence that even spontaneous communities of strangers are self-organizing, the results have important implications for the governance of the Wikipedia commons and for the security of all online social platforms and associations.