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{{SocPsy}}
 
{{SocPsy}}
'''Dunbar's number''' is a value significant in [[sociology]] and [[anthropology]]. Proposed by [[United Kingdom|British]] anthropologist [[Robin Dunbar]], it measures the "cognitive limit to the number of individuals with whom any one person can maintain stable relationships". Dunbar theorizes that "this limit is a direct function of relative [[neocortex]] size, and that this in turn limits group size ... the limit imposed by neocortical processing capacity is simply on the number of individuals with whom a stable inter-personal relationship can be maintained."
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'''Dunbar's number''' is a suggested [[Cognition|cognitive]] limit to the number of people with whom one can maintain stable [[Interpersonal relationship|social relationships]]. These are relationships in which an [[individual]] knows who each person is and how each person relates to every other person.<ref name="dunbar92"/><ref>{{cite pmid|23515066}}</ref><ref>{{cite pmid|22506743}}</ref><ref>{{cite pmid|22216422}}</ref><ref>{{cite pmid|21826200}}</ref><ref>{{cite book |last=Gladwell |first=Malcolm |title=The Tipping Point – How Little Things Make a Big Difference |year= 2000 |publisher=Little, Brown and Company |isbn=0-316-34662-4 |pages=177–181, 185–186}}</ref> This number was proposed by Dunbar, who found a correlation between primate brain size and average social group size. By using the average human brain size and extrapolating from the results of primates, he proposed that humans can only comfortably maintain 150 stable relationships <ref>Purves, D. (2008). Principles of cognitive neuroscience. Sinauer Associates Inc.</ref>. Proponents assert that numbers larger than this generally require more restrictive rules, laws, and enforced norms to maintain a stable, cohesive [[social group|group]]. It has been proposed to lie between 100 and 230, with a commonly used value of 150.<ref>{{Cite paper |arxiv=0905.3704 |title=Unravelling the size distribution of social groups with information theory on complex networks |work=Preprint |year=2009 |first=A. |last=Hernando |first2=D. |last2=Villuendas |first3=C. |last3=Vesperinas |first4=M. |last4=Abad |first5=A. |last5=Plastino }}</ref><ref>{{cite news |url=http://www.npr.org/2011/06/04/136723316/dont-believe-facebook-you-only-have-150-friends |title=Don't Believe Facebook; You Only Have 150 Friends |work=NPR |date=4 June 2011 }}</ref> Dunbar's number states the number of people one knows and keeps social contact with, and it does not include the number of people known personally with a ceased social relationship, nor people just generally known with a lack of persistent social relationship, a number which might be much higher and likely depends on [[long-term memory]] size.
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Dunbar's number was first proposed by British [[Anthropology|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 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 [[Friendship|friends]], with whom a person would want to reacquaint themself if they met again.<ref>{{cite news |title=Sorry, You May Have Gone Over Your Limit Of Network Friends |url=http://online.wsj.com/article/SB119518271549595364.html?mod=googlenews_wsj |author=Carl Bialik |date=16 November 2007 |publisher=The Wall Street Journal Online |accessdate=2007-12-02}}</ref>
   
 
== Research background ==
 
== Research background ==
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Dunbar's number has since become a major [[meme]] of interest in anthropology, sociology, [[statistics]], and [[business management]]. As with many theoretical values, it has occasionally been abused and mistaken as a "magic number".
 
Dunbar's number has since become a major [[meme]] of interest in anthropology, sociology, [[statistics]], and [[business management]]. As with many theoretical values, it has occasionally been abused and mistaken as a "magic number".
   
== Popularization ==
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==Alternative numbers==
Dunbar's number has been most popularized by [[Malcolm Gladwell]]'s ''[[The Tipping Point (book)|The Tipping Point]]'', where it plays a central role in Gladwell's arguments about the dynamics of social groups. In a 1985 paper titled [http://www.dennisfox.net/papers/commons.html "Psychology, Ideology, Utopia, & the Commons,"] psychologist Dennis Fox proposed the same concept as it is applied to [[anarchy]], [[politics]], and the [[tragedy of the commons]].
 
   
It has also been popularized as the '''monkeysphere''', a [[neologism]] coined by David Wong in an article which introduces this concept in a humorous manner.
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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, which is roughly double Dunbar's estimate. The Bernard–Killworth [[median]] of 231 is lower, due to{{Citation needed|date=April 2013}} upward straggle in the distribution, but still appreciably larger than Dunbar's estimate. 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. It is not an average of study averages but a repeated finding.<ref>{{cite journal |last=McCarty |first=C. |last2=Killworth |first2=P. D. |last3=Bernard |first3=H. R. |last4=Johnsen |first4=E. |last5=Shelley |first5=G. |title=Comparing Two Methods for Estimating Network Size |journal=Human Organization |volume=60 |issue=1 |pages=28–39 |year=2000 |doi= |url=http://sfaa.metapress.com/link.asp?id=efx5t9gjtgmga73y }}</ref><ref>{{cite doi|10.1016/0378-8733(87)90017-7}}</ref><ref>H. Russell Bernard. "Honoring Peter Killworth's contribution to social network theory." Paper presented to the University of Southampton, 28 September 2006. http://nersp.osg.ufl.edu/~ufruss/</ref> Nevertheless, the Bernard–Killworth number has not been popularized as widely as Dunbar's.
   
In its popularization, the research of Dunbar and others is taken as an upper bound of the number of fellow humans that an individual can view as being "truly human". In this form, the "monkeysphere" functions as a [[reductionism|reductionistic]] and biologistic explanation for why humans can treat some humans with consideration and other humans indifferently or even inhumanely.
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==See also==
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* [[Allen curve]]
Some example explanations using the notion of a monkeysphere are:
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* [[Bowling Alone]]
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* [[Continuum concept]]
* "Whenever you make new close personal friends, you have to drop some old personal friends to make room for them in your monkeysphere."
 
* "The reason that the people in village ''X'' don't mind doing ''Y'' to the people in village ''Z'' is because the people in village ''Z'' are not in the monkeysphere of people in village ''X''."
 
* "Because the number of people in that department exceeded 150, which is the size of the human monkeysphere, they had to split the department into two."
 
 
Recently, the number has been used in the study of [[Internet community|Internet communities]], especially [[MMORPG]]s such as [[Ultima Online]]. [[Neo-Tribalism|Neo-Tribalists]] have also used it to support their critiques of modern society.
 
   
 
==References==
 
==References==
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* [http://www.bbsonline.org/documents/a/00/00/05/65/bbs00000565-00/bbs.dunbar.html A pre-publication version] of ''Coevolution of neocortical size, group size and language in humans''. (See also Bibliography section there.)
 
* [http://www.bbsonline.org/documents/a/00/00/05/65/bbs00000565-00/bbs.dunbar.html A pre-publication version] of ''Coevolution of neocortical size, group size and language in humans''. (See also Bibliography section there.)
 
*[http://www.liv.ac.uk/researchintelligence/issue17/brainteaser.html University of Liverpool Research Intelligence No. 17, August 2003] - "The ultimate brain teaser" - an article on Dunbar's research.
 
*[http://www.liv.ac.uk/researchintelligence/issue17/brainteaser.html University of Liverpool Research Intelligence No. 17, August 2003] - "The ultimate brain teaser" - an article on Dunbar's research.
*[http://www.pointlesswasteoftime.com/monkeysphere.html Inside the Monkeysphere by David Wong] - a humorous introduction to the notion of the monkeysphere.
 
*[http://mythical.blogspot.com/2004_06_01_mythical_archive.html Some speculations] about a correlation between the monkeysphere and [[guild]] size in online multiplayer role playing games. (404)
 
 
*[http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html Detailed article about Dunbar's number and its application to online gaming]
 
*[http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html Detailed article about Dunbar's number and its application to online gaming]
 
*[http://www.blog.mopsos.com/archives/000075.html Mospos blog entry] - Communities of practice and Dunbar's number
 
*[http://www.blog.mopsos.com/archives/000075.html Mospos blog entry] - Communities of practice and Dunbar's number
*[http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html Life With Alacrity blog entry] - A blog on social software, collaboration, trust, security, privacy, and internet tools, by Christopher Allen.
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[[Category:Anthropology]]
 
[[Category:Anthropology]]

Latest revision as of 21:27, September 7, 2013

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Dunbar's number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships. These are relationships in which an individual knows who each person is and how each person relates to every other person.[1][2][3][4][5][6] This number was proposed by Dunbar, who found a correlation between primate brain size and average social group size. By using the average human brain size and extrapolating from the results of primates, he proposed that humans can only comfortably maintain 150 stable relationships [7]. Proponents assert that numbers larger than this generally require more restrictive rules, laws, and enforced norms to maintain a stable, cohesive group. It has been proposed to lie between 100 and 230, with a commonly used value of 150.[8][9] Dunbar's number states the number of people one knows and keeps social contact with, and it does not include the number of people known personally with a ceased social relationship, nor people just generally known with a lack of persistent social relationship, a number which might be much higher and likely depends on long-term memory size.

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 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 themself if they met again.[10]

Research background Edit

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. 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. Using a regression equation on data for 38 primate genera, Dunbar predicted a human "mean group size" of 147.8 (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. 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.

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.

Dunbar has theorized 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. 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 proposes furthermore that language may have arisen as a "cheap" means of social grooming, allowing early humans to efficiently maintain social cohesion. 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.

Dunbar's number has since become a major meme of interest in anthropology, sociology, statistics, and business management. As with many theoretical values, it has occasionally been abused and mistaken as a "magic number".

Alternative numbersEdit

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, which is roughly double Dunbar's estimate. The Bernard–Killworth median of 231 is lower, due to[citation needed] upward straggle in the distribution, but still appreciably larger than Dunbar's estimate. 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. It is not an average of study averages but a repeated finding.[11][12][13] Nevertheless, the Bernard–Killworth number has not been popularized as widely as Dunbar's.

See alsoEdit

ReferencesEdit

  • Sawaguchi, T., & Kudo, H. (1990), Neocortical development and social structure in primates, Primates 31: 283-290.
  • Dunbar, R.I.M. (1992) Neocortex size as a constraint on group size in primates, Journal of Human Evolution 22: 469-493.
  • Dunbar, R.I.M. (1993), Coevolution of neocortical size, group size and language in humans, Behavioral and Brain Sciences 16 (4): 681-735.

External linksEdit

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