| Records |
| Author |
Shultz, S.; Dunbar, R.I.M. |
Title  |
Both social and ecological factors predict ungulate brain size |
Type |
Journal Article |
| Year |
2006 |
Publication |
Proceedings. Biological Sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
273 |
Issue |
1583 |
Pages |
207-215 |
| Keywords |
Animals; Artiodactyla/*anatomy & histology/*physiology; Brain/*anatomy & histology/physiology; *Ecosystem; Organ Size; Perissodactyla/*anatomy & histology/*physiology; *Social Behavior |
| Abstract |
Among mammals, the members of some Orders have relatively large brains. Alternative explanations for this have emphasized either social or ecological selection pressures favouring greater information-processing capacities, including large group size, greater foraging efficiency, higher innovation rates, better invasion success and complex problem solving. However, the focal taxa for these analyses (primates, carnivores and birds) often show both varied ecological competence and social complexity. Here, we focus on the specific relationship between social complexity and brain size in ungulates, a group with relatively simple patterns of resource use, but extremely varied social behaviours. The statistical approach we used, phylogenetic generalized least squares, showed that relative brain size was independently associated with sociality and social complexity as well as with habitat use, while relative neocortex size is associated with social but not ecological factors. A simple index of sociality was a better predictor of both total brain and neocortex size than group size, which may indicate that the cognitive demands of sociality depend on the nature of social relationships as well as the total number of individuals in a group. |
| Address |
School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK. susanne.shultz@liv.ac.uk |
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0962-8452 |
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PMID:16555789 |
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no |
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2098 |
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| Author |
Stanley, C.R.; Dunbar, R.I.M. |
| Title |
Consistent social structure and optimal clique size revealed by social network analysis of feral goats, Capra hircus |
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Journal Article |
| Year |
2013 |
Publication |
Anim Behav |
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85 |
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Equine Behaviour @ team @ Stanley2013 |
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6253 |
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Dunbar, R.I.; Dunbar, E.P. |
| Title |
Contrasts in social structure among black-and-white colobus monkey groups |
Type |
Journal Article |
| Year |
1976 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
24 |
Issue |
1 |
Pages |
84-92 |
| Keywords |
Agonistic Behavior; Animals; *Colobus; Copulation; Female; *Haplorhini; *Hierarchy, Social; Male; *Social Dominance |
| Abstract |
Three types of Colobus guereza groups may be distinguished on the bases of size and composition, namely small one-male groups, large, one-male groups and multi-male groups. The social structure of each type of group is described in terms of the distribution of non-agonistic interactions, the frequency and distribution of agonistic behaviour and the organization of the roles of vigilance, territorial defence and leadership. A number of differences are found between the group types which appear to be related to the differences in group size and composition. It is suggested that these group types represent stages in the life-cycle of colobus groups, and that such an interpretation may help to resolve some of the conflicting reports in the literature. |
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0003-3472 |
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PMID:817624 |
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2049 |
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| Author |
Zhou, W.-X.; Sornette, D.; Hill, R.A.; Dunbar, R.I.M. |
| Title |
Discrete hierarchical organization of social group sizes |
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Journal Article |
| Year |
2005 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
272 |
Issue |
1561 |
Pages |
439-444 |
| Keywords |
Anthropology, Cultural; *Group Structure; Humans; *Models, Biological; *Social Behavior; *Social Environment |
| Abstract |
The 'social brain hypothesis' for the evolution of large brains in primates has led to evidence for the coevolution of neocortical size and social group sizes, suggesting that there is a cognitive constraint on group size that depends, in some way, on the volume of neural material available for processing and synthesizing information on social relationships. More recently, work on both human and non-human primates has suggested that social groups are often hierarchically structured. We combine data on human grouping patterns in a comprehensive and systematic study. Using fractal analysis, we identify, with high statistical confidence, a discrete hierarchy of group sizes with a preferred scaling ratio close to three: rather than a single or a continuous spectrum of group sizes, humans spontaneously form groups of preferred sizes organized in a geometrical series approximating 3-5, 9-15, 30-45, etc. Such discrete scale invariance could be related to that identified in signatures of herding behaviour in financial markets and might reflect a hierarchical processing of social nearness by human brains. |
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State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237, China |
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0962-8452 |
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PMID:15734699 |
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no |
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refbase @ user @ |
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549 |
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| Author |
Shi, J.; Dunbar, R.I.M.; Buckland, D.; Miller, D. |
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Dynamics of grouping patterns and social segregation in feral goats (Capra hircus) on the Isle of Rum, NW Scotland |
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Journal Article |
| Year |
2005 |
Publication |
Mammalia |
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69 |
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Equine Behaviour @ team @ Shi2005 |
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6257 |
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| Author |
Pérez-Barbería, F.J.; Shultz, S.; Dunbar, R.I.M.; Janis, C. |
| Title |
Evidence For Coevolution Of Sociality And Relative Brain Size In Three Orders Of Mammals |
Type |
Journal Article |
| Year |
2007 |
Publication |
Evolution |
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61 |
Issue |
12 |
Pages |
2811-2821 |
| Keywords |
Brain size, carnivores, coevolution, primates, sociality, ungulates |
| Abstract |
Abstract
As the brain is responsible for managing an individual's behavioral response to its environment, we should expect that large relative brain size is an evolutionary response to cognitively challenging behaviors. The “social brain hypothesis†argues that maintaining group cohesion is cognitively demanding as individuals living in groups need to be able to resolve conflicts that impact on their ability to meet resource requirements. If sociality does impose cognitive demands, we expect changes in relative brain size and sociality to be coupled over evolutionary time. In this study, we analyze data on sociality and relative brain size for 206 species of ungulates, carnivores, and primates and provide, for the first time, evidence that changes in sociality and relative brain size are closely correlated over evolutionary time for all three mammalian orders. This suggests a process of coevolution and provides support for the social brain theory. However, differences between taxonomic orders in the stability of the transition between small-brained/nonsocial and large-brained/social imply that, although sociality is cognitively demanding, sociality and relative brain size can become decoupled in some cases. Carnivores seem to have been especially prone to this. |
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doi: 10.1111/j.1558-5646.2007.00229.x |
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Equine Behaviour @ team @ |
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4781 |
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Pérez-Barbería, F.J.; Shultz, S.; Dunbar, R.I. |
| Title |
Evidence for coevolution of sociality and relative brain size in three orders of mammals |
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Journal Article |
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2007 |
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Evolution |
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61 |
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Equine Behaviour @ team @ Pérez-Barbería2007 |
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6221 |
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| Author |
Dunbar, R.I.M.; Shultz, S. |
| Title |
Evolution in the Social Brain |
Type |
Journal Article |
| Year |
2007 |
Publication |
Science |
Abbreviated Journal |
Science |
| Volume |
317 |
Issue |
5843 |
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1344-1347 |
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The evolution of unusually large brains in some groups of animals, notably primates, has long been a puzzle. Although early explanations tended to emphasize the brain's role in sensory or technical competence (foraging skills, innovations, and way-finding), the balance of evidence now clearly favors the suggestion that it was the computational demands of living in large, complex societies that selected for large brains. However, recent analyses suggest that it may have been the particular demands of the more intense forms of pairbonding that was the critical factor that triggered this evolutionary development. This may explain why primate sociality seems to be so different from that found in most other birds and mammals: Primate sociality is based on bonded relationships of a kind that are found only in pairbonds in other taxa. |
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Equine Behaviour @ team @ |
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4243 |
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Dunbar, R.I.M. |
| Title |
Male and female brain evolution is subject to contrasting selection pressures in primates |
Type |
Journal Article |
| Year |
2007 |
Publication |
BMC Biology |
Abbreviated Journal |
BMC Biol |
| Volume |
5 |
Issue |
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Pages |
21 |
| Keywords |
Animals; *Brain/physiology; *Evolution; Female; Humans; Male; *Selection (Genetics); *Sex Characteristics |
| Abstract |
The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the “social brain” hypothesis) is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20) add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative) is related most closely to neocortex volume, but male sociality (which is more competitive and combative) is more closely related to subcortical units (notably those associated with emotional responses). Thus different brain units have responded to different selection pressures. |
| Address |
British Academy Centenary Research Project, School of Biological Sciences, University of Liverpool, Liverpool, UK. rimd@liv.ac.uk |
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1741-7007 |
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PMID:17493267 |
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no |
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2100 |
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Dunbar, R.I.M.; McAdam, M.R.; O'connell, S. |
| Title |
Mental rehearsal in great apes (Pan troglodytes and Pongo pygmaeus) and children |
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Journal Article |
| Year |
2005 |
Publication |
Behavioural Processes |
Abbreviated Journal |
Behav. Process. |
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69 |
Issue |
3 |
Pages |
323-330 |
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Algorithms; Animals; Child; Child, Preschool; Food; Frontal Lobe/anatomy & histology/physiology; Humans; *Imagination; Pan troglodytes; Pongo pygmaeus; Problem Solving/*physiology; Psychomotor Performance/physiology; Reward |
| Abstract |
The ability to rehearse possible future courses of action in the mind is an important feature of advanced social cognition in humans, and the “social brain” hypothesis implies that it might also be a feature of primate social cognition. We tested two chimpanzees, six orangutans and 63 children aged 3-7 years on a set of four puzzle boxes, half of which were presented with an opportunity to observe the box before being allowed to open it (“prior view”), the others being given without an opportunity to examine the boxes before handling them (“no prior view”). When learning effects are partialled out, puzzle boxes in the “prior view” condition were opened significantly faster than boxes given in the “no prior view” condition by the children, but not by either of the great apes. The three species differ significantly in the speed with which they opened boxes in the “no prior view” condition. The three species' performance on this task was a function of relative frontal lobe volume, suggesting that it may be possible to identify quantitative neuropsychological differences between species. |
| Address |
Evolutionary Psychology Research Group, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK. rimd@liv.ac.uk |
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0376-6357 |
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PMID:15896530 |
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2097 |
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