| Records |
| Author |
Conradt, L.; Roper, T.J. |
| Title |
Group decision-making in animals |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
421 |
Issue |
6919 |
Pages |
155-158 |
| Keywords |
Animals; Behavior, Animal/*physiology; *Decision Making; Democracy; Group Processes; *Models, Biological; Population Density; Social Behavior |
| Abstract |
Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans. |
| Address |
School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK. l.conradt@sussex.ac.uk |
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English |
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| ISSN |
0028-0836 |
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Notes  |
PMID:12520299 |
Approved |
no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
5136 |
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| Author |
Johnson, D.D.P.; Stopka, P.; Knights, S. |
| Title |
Sociology: The puzzle of human cooperation |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
421 |
Issue |
6926 |
Pages |
911-2; discussion 912 |
| Keywords |
Altruism; *Cooperative Behavior; Evolution; Humans; *Models, Biological; Punishment; Reward; Risk |
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| Address |
Olin Institute for Strategic Studies, Harvard University, Cambridge, Massachusetts 02138, USA. dominic@post.harvard.edu |
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English |
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0028-0836 |
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| Notes |
PMID:12606989 |
Approved |
no |
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refbase @ user @ |
Serial |
467 |
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| Author |
Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A. |
| Title |
Spontaneous emergence of leaders and followers in foraging pairs |
Type |
Journal Article |
| Year |
2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
423 |
Issue |
6938 |
Pages |
432-434 |
| Keywords |
Animals; *Energy Metabolism; Food; *Food Chain; *Models, Biological; Motor Activity; *Social Behavior; Time Factors |
| Abstract |
Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of foraging by a pair of animals, in which each individual chooses between resting or foraging during a series of consecutive periods, so as to maximize its own individual chances of survival. We find that, if there is an advantage to foraging together, the equilibrium behaviour of both individuals becomes highly synchronized. As a result of this synchronization, differences in the energetic reserves of the two players spontaneously develop, leading them to adopt different behavioural roles. The individual with lower reserves emerges as the 'pace-maker' who determines when the pair should forage, providing a straightforward resolution to the problem of group coordination. Moreover, the strategy that gives rise to this behaviour can be implemented by a simple 'rule of thumb' that requires no detailed knowledge of the state of other individuals. |
| Address |
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. s.rands@zoo.cam.ac.uk |
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English |
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0028-0836 |
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| Notes |
PMID:12761547 |
Approved |
no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
5138 |
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| Author |
Dubois, F.; Giraldeau, L.-A. |
| Title |
The forager's dilemma: food sharing and food defense as risk-sensitive foraging options |
Type |
Journal Article |
| Year |
2003 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
162 |
Issue |
6 |
Pages |
768-779 |
| Keywords |
Animals; Competitive Behavior/*physiology; *Environment; Feeding Behavior/*physiology; *Game Theory; *Models, Biological; Population Density; Population Dynamics |
| Abstract |
Although many variants of the hawk-dove game predict the frequency at which group foraging animals should compete aggressively, none of them can explain why a large number of group foraging animals share food clumps without any overt aggression. One reason for this shortcoming is that hawk-dove games typically consider only a single contest, while most group foraging situations involve opponents that interact repeatedly over discovered food clumps. The present iterated hawk-dove game predicts that in situations that are analogous to a prisoner's dilemma, animals should share the resources without aggression, provided that the number of simultaneously available food clumps is sufficiently large and the number of competitors is relatively small. However, given that the expected gain of an aggressive animal is more variable than the gain expected by nonaggressive individuals, the predicted effect of the number of food items in a clump-clump richness-depends on whether only the mean or both the mean and variability associated with payoffs are considered. More precisely, the deterministic game predicts that aggression should increase with clump richness, whereas the stochastic risk-sensitive game predicts that the frequency of encounters resulting in aggression should peak at intermediate clump richnesses or decrease with increasing clump richness if animals show sensitivity to the variance or coefficient of variation, respectively. |
| Address |
Departement des Sciences Biologiques, Universite du Quebec a Montreal, Case postale 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada. fdubois@u-bourgogne.fr |
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English |
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0003-0147 |
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| Notes |
PMID:14737714 |
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no |
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Serial |
2132 |
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| Author |
Cameron, E.Z. |
| Title |
Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism |
Type |
Journal Article |
| Year |
2004 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
271 |
Issue |
1549 |
Pages |
1723-1728 |
| Keywords |
Age Factors; Animals; Body Constitution; *Evolution; Female; Glucose/metabolism/physiology; Litter Size; Male; Mammals/*physiology; *Models, Biological; Reproduction/physiology; Seasons; Sex Factors; *Sex Ratio; Time Factors |
| Abstract |
Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios. |
| Address |
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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English |
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Edition |
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0962-8452 |
ISBN |
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| Notes |
PMID:15306293 |
Approved |
no |
| Call Number |
refbase @ user @ |
Serial |
413 |
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| Author |
Uehara, T.; Yokomizo, H.; Iwasa, Y. |
| Title |
Mate-choice copying as Bayesian decision making |
Type |
Journal Article |
| Year |
2005 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
| Volume |
165 |
Issue |
3 |
Pages |
403-410 |
| Keywords |
Animals; *Bayes Theorem; *Choice Behavior; Female; Male; *Models, Biological; *Sexual Behavior, Animal |
| Abstract |
Mate-choice copying by females has been reported in fishes (e.g., guppies) and lekking birds. Presumably, females assess males' quality using both information from direct observation of males and information acquired by observing other females' choices. Here, we study mathematically the conditions under which mate-choice copying is advantageous on the basis of Bayesian decision theory. A female may observe the mate choice of another female, called the model female, who has performed an optimal choice based on her own judgment. The conditions required for the focal female to choose the same mate as that chosen by the model female should depend on the male's appearance to her, the reliability of her own judgment of male quality, and the reliability of the model females. When three or more females are involved, the optimal mate choice critically depends on whether multiple model females make decisions independently or they themselves copy the choices of others. If two equally reliable females choose different males, the choice of the second female, made knowing the choice of the first, should have a stronger effect on the choice of the third (focal) female. This “last-choice precedence” should be tested experimentally. |
| Address |
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. uehara@bio-math.biology.kyushu-u.ac.jp |
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English |
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Edition |
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| ISSN |
1537-5323 |
ISBN |
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| Notes |
PMID:15729669 |
Approved |
no |
| Call Number |
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Serial |
1821 |
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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 |
Type |
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. |
| Address |
State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237, China |
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English |
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0962-8452 |
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| Notes |
PMID:15734699 |
Approved |
no |
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refbase @ user @ |
Serial |
549 |
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| Author |
Izar, P.; Ferreira, R.G.; Sato, T. |
| Title |
Describing the organization of dominance relationships by dominance-directed tree method |
Type |
Journal Article |
| Year |
2006 |
Publication |
American journal of primatology |
Abbreviated Journal |
Am. J. Primatol. |
| Volume |
68 |
Issue |
2 |
Pages |
189-207 |
| Keywords |
Animals; Cebus/physiology; *Models, Biological; *Social Dominance |
| Abstract |
Methods to describe dominance hierarchies are a key tool in primatology studies. Most current methods are appropriate for analyzing linear and near-linear hierarchies; however, more complex structures are common in primate groups. We propose a method termed “dominance-directed tree.” This method is based on graph theory and set theory to analyze dominance relationships in social groups. The method constructs a transitive matrix by imposing transitivity to the dominance matrix and produces a graphical representation of the dominance relationships, which allows an easy visualization of the hierarchical position of the individuals, or subsets of individuals. The method is also able to detect partial and complete hierarchies, and to describe situations in which hierarchical and nonhierarchical principles operate. To illustrate the method, we apply a dominance tree analysis to artificial data and empirical data from a group of Cebus apella. |
| Address |
Department of Experimental Psychology, University of Sao Paulo, Brazil. patrizar@usp.br |
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English |
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0275-2565 |
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| Notes |
PMID:16429416 |
Approved |
no |
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refbase @ user @ |
Serial |
723 |
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| Author |
Scheffer, M.; van Nes, E.H. |
| Title |
Self-organized similarity, the evolutionary emergence of groups of similar species |
Type |
Journal Article |
| Year |
2006 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
| Volume |
103 |
Issue |
16 |
Pages |
6230-6235 |
| Keywords |
Animals; *Competitive Behavior; *Ecosystem; *Evolution; *Models, Biological |
| Abstract |
Ecologists have long been puzzled by the fact that there are so many similar species in nature. Here we show that self-organized clusters of look-a-likes may emerge spontaneously from coevolution of competitors. The explanation is that there are two alternative ways to survive together: being sufficiently different or being sufficiently similar. Using a model based on classical competition theory, we demonstrate a tendency for evolutionary emergence of regularly spaced lumps of similar species along a niche axis. Indeed, such lumpy patterns are commonly observed in size distributions of organisms ranging from algae, zooplankton, and beetles to birds and mammals, and could not be well explained by earlier theory. Our results suggest that these patterns may represent self-constructed niches emerging from competitive interactions. A corollary of our findings is that, whereas in species-poor communities sympatric speciation and invasion of open niches is possible, species-saturated communities may be characterized by convergent evolution and invasion by look-a-likes. |
| Address |
Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 8080, 6700 DD, Wageningen, The Netherlands. marten.scheffer@wur.nl |
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English |
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0027-8424 |
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| Notes |
PMID:16585519 |
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no |
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refbase @ user @ |
Serial |
510 |
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| Author |
Bell, A.M. |
| Title |
Evolutionary biology: animal personalities |
Type |
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| Year |
2007 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
447 |
Issue |
7144 |
Pages |
539-540 |
| Keywords |
Aggression/physiology/psychology; Animals; Behavior, Animal/*physiology; *Evolution; Humans; *Models, Biological; Personality/genetics/*physiology; Reproduction/genetics/physiology; Risk-Taking; Selection (Genetics) |
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Edition |
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| ISSN |
1476-4687 |
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| Notes |
PMID:17538607 |
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no |
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Equine Behaviour @ team @ |
Serial |
4099 |
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