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See also: Dunbar (disambiguation)

Dunbar's number is the supposed cognitive limit to the number of individuals with whom any one person can maintain stable social relationships: the kind of relationships that go with knowing who each person is and how each person relates socially to every other person. [1] Proponents assert that group sizes larger than this generally require more restricted rules, laws, and enforced policies and regulations to maintain a stable cohesion.

No precise value has been proposed for Dunbar's number, but a commonly cited approximate figure is 150.

Dunbar's number was first proposed by British anthropologist Robin Dunbar, who theorized that "this limit is a direct function of relative neocortex size, and that this in turn limits group size . The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Robin Ian MacDonald Dunbar (born June 28, 1947, Liverpool) is a British anthropologist and Evolutionary biologist specialising The neocortex ( Latin for "new Bark " or "new Rind " is a part of the Brain of Mammals It is the outer layer of . . the limit imposed by neocortical processing capacity is simply on the number of individuals with whom a stable inter-personal relationship can be maintained. " On the periphery, the number also includes past colleagues such as high school friends with whom a person would want to reacquaint themselves if they met again. [2]

Contents

Research background

Primatologists have noted that, due to their highly social nature, non-human primates have to maintain personal contact with the other members of their social group, usually through grooming. Primatology is the study of Primates It is a diverse Discipline and primatologists can be found in departments of Biology, Anthropology A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye In Social animals and humans social grooming or allogrooming is an activity in which individuals in a group clean or maintain each other's body or appearance Such social groups function as protective cliques within the physical groups in which the primates live. The number of social group members a primate can track appears to be limited by the volume of the neocortex region of their brain. This suggests that there is a species-specific index of the social group size, computable from the species' mean neocortex volume.

In a 1992 article, Dunbar used the correlation observed for non-human primates to predict a social group size for humans. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Using a regression equation on data for 38 primate genera, Dunbar predicted a human "mean group size" of 148 (casually represented as 150), a result he considered exploratory due to the large error measure (a 95% confidence interval of 100 to 230).

Dunbar then compared this prediction with observable group sizes for humans. Beginning with the assumption that the current mean size of the human neocortex had developed about 250,000 years BCE, i. e. during the Pleistocene, Dunbar searched the anthropological and ethnographical literature for census-like group size information for various hunter-gatherer societies, the closest existing approximations to how anthropology reconstructs the Pleistocene societies. The Pleistocene ('plaɪstəsin is the epoch from 18 million to 10000 years BP covering the world's recent period Anthropology (/ˌænθɹəˈpɒlədʒi/ from Greek grc ἄνθρωπος anthrōpos, "human" -λογία -logia) is the study of Ethnography ( Greek ethnos = people and graphein = writing is a genre of writing that uses Fieldwork to provide a descriptive A hunter-gatherer society is one whose primary subsistence method involves the direct procurement of edible plants and animals from the wild Foraging and Hunting Dunbar noted that the groups fell into three categories — small, medium and large, equivalent to bands, cultural lineage groups and tribes — with respective size ranges of 30-50, 100-200 and 500-2500 members each. A band society is the simplest form of human Society. A band generally consists of a small kin group no larger than an Extended family or Clan. A tribe, viewed historically or developmentally consists of a Social group existing before the development of or outside of States Many anthropologists use

Dunbar's surveys of village and tribe sizes also appeared to approximate this predicted value, including 150 as the estimated size of a neolithic farming village; 150 as the splitting point of Hutterite settlements; 200 as the upper bound on the number of academics in a discipline's sub-specialization; 150 as the basic unit size of professional armies in Roman antiquity and in modern times since the 16th century; and notions of appropriate company size. A village is a clustered human settlement or community, larger than a hamlet, but smaller than a Town or City. The Neolithic (from Greek νεολιθικός — neolithikos from νέος neos, "new" + λίθος lithos Hutterites are a communal branch of Anabaptists who like the Amish and Mennonites, trace their roots to the Radical Reformation of the 16th century An army (from Latin Armata "act of arming" via Old French armée) in the broadest sense is the land-based Armed forces Ancient Rome was a Civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC The term modern period or modern era (sometimes also modern times) is the period of history that followed the Middle Ages between c

Dunbar has argued that 150 would be the mean group size only for communities with a very high incentive to remain together. For a group of this size to remain cohesive, Dunbar speculated that as much as 42% of the group's time would have to be devoted to social grooming. Correspondingly, only groups under intense survival pressure, such as subsistence villages, nomadic tribes, and historical military groupings have, on average, achieved the 150-member mark. Subsistence agriculture is self-sufficient farming in which farmers grow only enough food to feed the family and to pay taxes or feudal dues Nomadic people, (from the νομάδες nomádes, "those who let pasture herds" also known as nomads, are communities of people that War is an international relations Dispute, characterized by organized Violence between National Military units Moreover, Dunbar noted that such groups are almost always physically close: ". . . we might expect the upper limit on group size to depend on the degree of social dispersal. In dispersed societies, individuals will meet less often and will thus be less familiar with each, so group sizes should be smaller in consequence. " Thus, the 150-member group would only occur because of absolute necessity, i. e. due to intense environmental and economic pressures.

Dunbar, author of Grooming, Gossip, and the Evolution of Language, proposes furthermore that language may have arisen as a "cheap" means of social grooming, allowing early humans to efficiently maintain social cohesion. A language is a dynamic set of visual auditory or tactile Symbols of Communication and the elements used to manipulate them Without language, Dunbar speculates, humans would have to expend nearly half their time on social grooming, which would have made productive, cooperative effort nearly impossible. Language may have allowed societies to remain cohesive, while reducing the need for physical and social intimacy. [3]

Dunbar's number has since become of interest in anthropology, evolutionary psychology,[4] statistics, and business management. Evolutionary psychology ( EP) attempts to explain mental and psychological traits such as Memory, Perception, Statistics is a mathematical science pertaining to the collection analysis interpretation or explanation and presentation of Data. Management (covering theory practice and scope of management and Manager' (covering the people who manage might help clarify and systematise Developers of social software are interested in it, as they need to know the size of social networks their software needs to take into account.

Alternative numbers

Dunbar's number is not derived from systematic observation of the number of relationships that people living in the contemporary world have. As noted above, it comes from extrapolation from nonhuman primates and from inspection of selected documents showing network sizes in selected pre-industrial villages and settlements in less developed countries. A social network is a Social structure made of nodes (which are generally individuals or organizations that are tied by one or more specific types of interdependency such as

Anthropologist H. Russell Bernard and Peter Killworth and associates have done a variety of field studies in the United States that came up with an estimated mean number of ties - 290 - that is roughly double Dunbar's estimate. The Bernard-Killworth median of 231 is lower, due to upward straggle in the distribution: this is still appreciably larger than Dunbar's estimate. In Probability theory and Statistics, a median is described as the number separating the higher half of a sample a population or a Probability distribution The Bernard-Killworth estimate of the maximum likelihood of the size of a person's social network is based on a number of field studies using different methods in various populations. A social network is a Social structure made of nodes (which are generally individuals or organizations that are tied by one or more specific types of interdependency such as It is not an average of study averages but a repeated finding. [5][6] Nevertheless, the Bernard-Killworth number has not been popularized as widely as Dunbar's.

Popularization

References

  1. ^ Gladwell, Malcolm (2000). The Tipping Point - How Little Things Make a Big Difference. Little, Brown and Company. ISBN 0-316-34662-4.  
  2. ^ Carl Bialik. "Sorry, You May Have Gone Over Your Limit Of Network Friends", November 16, 2007. Retrieved on 2007-12-02. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1409 - The University of Leipzig opens 1755 - The second Eddystone Lighthouse is destroyed by fire  
  3. ^ Grooming, Gossip, and the Evolution of Language (Paperback) by Robin Dunbar (Author). amazon. com. Retrieved on 2007-12-02. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1409 - The University of Leipzig opens 1755 - The second Eddystone Lighthouse is destroyed by fire
  4. ^ Nuno Themudo (March 23, 2007). Virtual Resistance: Internet-mediated Networks (Dotcauses) and Collective Action Against Neoliberalism (pg. 36). University of Pittsburg, University Center for Internation Studies. Retrieved on 2007-12-02. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1409 - The University of Leipzig opens 1755 - The second Eddystone Lighthouse is destroyed by fire
  5. ^ McCarty,C. , Killworth, P. D. , Bernard,H. R. , Johnsen, E. and Shelley, G. “Comparing Two Methods for Estimating Network Size”, Human Organization 60:28-39. (2000).
  6. ^ Bernard, H. Russell, Gene Ann Shelley and Peter Killworth. 1987. "How Much of a Network does the GSS and RSW Dredge Up?" Social Networks 9: 49-63. H. Russell Bernard. 2006. "Honoring Peter Killworth's contribution to social network theory. " Paper presented to the University of Southampton, September. http://nersp.osg.ufl.edu/~ufruss/
  7. ^ David Wong. Inside the Monkeysphere. Retrieved on 2007-12-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 274 - Roman Emperor Aurelian
  8. ^ One example is Christopher Allen, "Dunbar, Altruistic Punishment, and Meta-Moderation".
  9. ^ The Local – Sweden's news in English, July 23, 2007. Events 1632 - Three hundred colonists bound for New France depart from Dieppe France. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. "Swedish tax collectors organized by apes".

Further reading

External links

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