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Author |
Bergstrom, C.T.; Lachmann, M. |
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Title |
Signaling among relatives. III. Talk is cheap |
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Journal Article |
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Year |
1998 |
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Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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95 |
Issue |
9 |
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5100-5105 |
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Animal Communication; Animals; Costs and Cost Analysis; *Evolution; Interpersonal Relations; Models, Biological |
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The Sir Philip Sidney game has been used by numerous authors to show how signal cost can facilitate honest signaling among relatives. Here, we demonstrate that, in this game, honest cost-free signals are possible as well, under very general conditions. Moreover, these cost-free signals are better for all participants than the previously explored alternatives. Recent empirical evidence suggests that begging is energetically inexpensive for nestling birds; this finding led some researchers to question the applicability of the costly signaling framework to nestling begging. Our results show that cost-free or inexpensive signals, as observed empirically, fall within the framework of signaling theory. |
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Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. carl@charles.stanford.edu |
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0027-8424 |
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PMID:9560235 |
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refbase @ user @ |
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561 |
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Author |
Dugatkin, L.A. |
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Title |
Breaking up fights between others: a model of intervention behaviour |
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Journal Article |
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Year |
1998 |
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Proceedings of the Royal Society of London. Series B: Biological Sciences |
Abbreviated Journal |
Proc. R. Soc. Lond. B |
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265 |
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1394 |
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433-437 |
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To examine when and why animals break up fights between others in their group, I modelled whether ‘winner’ and ‘loser’ effects might be one element driving the evolution of intervention behaviour. I considered one particular type of intervention: when the intervener simply breaks up fights between two others, but does not favour either party in so doing. When victories at time T + 1 are more likely given a victory at time T (i.e. winner effects), intervention is often favoured. Intervention is favoured in these circumstances because the intervening party in essence stops others from ‘getting on a roll’ and climbing up any hierarchy that exists. However, when loser effects alone are at work (defeats at time T + 1 are more likely given a defeat at time T), breaking up fights between others is never selected. If both winner and loser effects are operating simultaneously, then the likelihood of intervention behaviour evolving is a function of the relative strength of these two effects. The greater the winner effect relative to the loser effect, the more likely intervention behaviour is to evolve. |
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10.1098/rspb.1998.0313 |
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Equine Behaviour @ team @ |
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5240 |
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Oliveira, R. F.; McGregor, P.K.; Latruffe, C. |
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Title |
Know thine enemy: fighting fish gather information from observing conspecific interactions |
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Journal Article |
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1998 |
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Proceedings of the Royal Society B: Biological Sciences |
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Proc. Roy. Soc. Lond. B Biol. Sci. |
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265 |
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1401 |
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1045-1049 |
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Many of the signals that animals use to communicate transmit relatively large distances and therefore encompass several potential signallers and receivers. This observation challenges the common characterization of animal communication systems as consisting of one signaller and one receiver. Furthermore, it suggests that the evolution of communication behaviour must be considered as occurring in the context of communication networks rather than dyads. Although considerations of selection pressures acting upon signallers in the context of communication networks have rarely been expressed in such terms, it has been noted that many signals exchanged during aggressive interactions will transmit far further than required for information transfer between the individuals directly involved, suggesting that these signals have been designed to be received by other, more distant, individuals. Here we consider the potential for receivers in communication networks to gather information, one aspect of which has been termed eavesdropping. We show that male Betta splendens monitor aggressive interactions between neighbouring conspecifics and use the information on relative fighting ability in subsequent aggressive interactions with the males they have observed. |
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Equine Behaviour @ team @ |
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2168 |
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Clement, T.S.; Weaver, J.E.; Sherburne, L.M.; Zentall, T.R. |
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Title |
Simultaneous discrimination learning in pigeons: value of S- affects the relative value of its associated S+ |
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Journal Article |
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Year |
1998 |
Publication |
The Quarterly journal of experimental psychology. B, Comparative and physiological psychology |
Abbreviated Journal |
Q J Exp Psychol B |
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51 |
Issue |
4 |
Pages |
363-378 |
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Animals; *Attention; Color Perception; Columbidae; *Discrimination Learning; Female; Male; *Motivation; Orientation; Transfer (Psychology) |
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In a simple simultaneous discrimination involving a positive stimulus (S+) and a negative stimulus (S-), it has been hypothesized that positive value can transfer from the S+ to the S- (thus increasing the relative value of the S-) and also that negative value can transfer from the S- to the S+ (thus diminishing the relative value of the S+; Fersen, Wynne, Delius, & Staddon, 1991). Evidence for positive value transfer has been reported in pigeons (e.g. Zentall & Sherburne, 1994). The purpose of the present experiments was to determine, in a simultaneous discrimination, whether the S- diminishes the value of the S+ or the S- is contrasted with the S+ (thus enhancing the value of the S+). In two experiments, we found evidence for contrast, rather than value transfer, attributable to simultaneous discrimination training. Thus, not only does the S+ appear to enhance the value of the S-, but the S- appears to enhance rather than reduce the value of the S+. |
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Department of Psychology, University of Kentucky, Lexington 40506-0044, USA |
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0272-4995 |
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PMID:9854439 |
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no |
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refbase @ user @ |
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252 |
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Brannon, E.M.; Terrace, H.S. |
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Title |
Ordering of the numerosities 1 to 9 by monkeys |
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Journal Article |
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Year |
1998 |
Publication |
Science (New York, N.Y.) |
Abbreviated Journal |
Science |
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Volume |
282 |
Issue |
5389 |
Pages |
746-749 |
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Animals; *Discrimination (Psychology); Macaca mulatta/*psychology; *Mathematics; *Mental Processes |
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A fundamental question in cognitive science is whether animals can represent numerosity (a property of a stimulus that is defined by the number of discriminable elements it contains) and use numerical representations computationally. Here, it was shown that rhesus monkeys represent the numerosity of visual stimuli and detect their ordinal disparity. Two monkeys were first trained to respond to exemplars of the numerosities 1 to 4 in an ascending numerical order (1 --> 2 --> 3 --> 4). As a control for non-numerical cues, exemplars were varied with respect to size, shape, and color. The monkeys were later tested, without reward, on their ability to order stimulus pairs composed of the novel numerosities 5 to 9. Both monkeys responded in an ascending order to the novel numerosities. These results show that rhesus monkeys represent the numerosities 1 to 9 on an ordinal scale. |
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Department of Psychology, Columbia University, New York, NY 10027, USA. liz@psych.columbia.edu |
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0036-8075 |
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PMID:9784133 |
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refbase @ user @ |
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606 |
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Author |
Lachmann M.; Bergstrom C.T. |
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Title |
Signalling among Relatives II. Beyond the Tower of Babel |
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Journal Article |
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Year |
1998 |
Publication |
Theoretical Population Biology |
Abbreviated Journal |
Theor. Pop. Biol. |
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54 |
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2 |
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146-160 |
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Models of costly signalling are commonly employed in evolutionary biology in order to explain how honest communication between individuals with conflicting interests can be stable. These models have focused primarily on a single type of honest signalling equilibrium, the separating equilibrium in which any two different signallers send distinct signals, thereby providing signal receivers with complete information. In this paper, we demonstrate that in signalling among relatives (modelled using the Sir Philip Sidney game), there is not one but a large number of possible signalling equilibria, most of which are pooling equilibria in which different types of signallers may share a common signal. We prove that in a general Sir Philip Sidney game, any partition of signallers into equi-signalling classes can have a stable signalling equilibrium if and only if it is a contiguous partition, and provide examples of such partitions. A similar (but slightly stricter) condition is shown to hold when signals are transmitted through a medium with signalling error. These results suggest a solution to a problem faced by previous signalling theory models: when we consider the separating equilibrium, signal cost is independent of the frequency of individuals sending that signal and, consequently, even very rare signaller types can drastically affect signal cost. Here, we show that by allowing these rare signallers to pool with more common signallers, signal cost can be greatly reduced. Copyright 1998 Academic Press. |
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refbase @ user @ |
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560 |
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Author |
McLaren I.P.L. |
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Title |
Animal Learning and Cognition: A neural network approach |
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1998 |
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Trends in Cognitive Sciences |
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Trends. Cognit. Sci. |
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2 |
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236-236 |
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Vallortigara G. |
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Minds of Their Own |
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1998 |
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Trends in Cognitive Sciences |
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Trends. Cognit. Sci. |
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2 |
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118-118 |
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Connor, R.C.; Mann, J.; Tyack, P.L.; Whitehead, H. |
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Title |
Social evolution in toothed whales |
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Journal Article |
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1998 |
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Trends in Ecology & Evolution |
Abbreviated Journal |
Trends. Ecol. Evol |
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13 |
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6 |
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228-232 |
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odontocetes; toothed whales; social evolution; communication; bottlenose dolphins; sperm whales; long-term studies; foraging |
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Two contrasting results emerge from comparisons of the social systems of several odontocetes with terrestrial mammals. Researchers have identified remarkable convergence in prominent features of the social systems of odontocetes such as the sperm whale and bottlenose dolphin with a few well-known terrestrial mammals such as the elephant and chimpanzee. In contrast, studies on killer whales and Baird's beaked whale reveal novel social solutions to aquatic living. The combination of convergent and novel features in odontocete social systems promise a more general understanding of the ecological determinants of social systems in both terrestrial and aquatic habitats, as well as the relationship between relative brain size and social evolution. |
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0169-5347 |
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Equine Behaviour @ team @ |
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4789 |
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Heitkamp, H.C.; Horstmann, T.; Hillgeris, D. |
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[Riding injuries and injuries due to handling horses in experienced riders] |
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1998 |
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Der Unfallchirurg |
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Unfallchirurg |
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101 |
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2 |
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122-128 |
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Adult; Animals; Athletic Injuries/*epidemiology/etiology/surgery; Cross-Sectional Studies; Female; Fractures, Bone/epidemiology/etiology/surgery; Germany/epidemiology; *Horses; Humans; Incidence; Male; Multiple Trauma/epidemiology/etiology/surgery; Risk Factors |
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A group of experienced riders who qualified for the German riding badge 9.5 years ago answered a questionnaire pertaining to injuries during jumping, dressage and cross-country riding, as well as handling the horse. During riding 69% of the persons had had 187 injuries and while handling the horse 52% had had 124 injuries. Fractures and contusions were the most-frequent injuries; most riding injuries were located in the upper extremities and shoulder while handling mainly in the hands and feet. The number of injuries was comparable in jumping, dressage or cross-country riding. The time engaged in jumping was about one-third of the other types of riding, but the injuries were more severe. While handling the horse the number of injuries relative to the time spent during the activity were higher but less complicated. No change in safety precautions had been implemented by 67% of the persons injured. The injury rate for equestrians is relatively low both in handling the horse and during riding. The frequent fractures and contusions may be reduced by following the required safety regulations. |
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Abteilung Sportmedizin, Universitat Tubingen |
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German |
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Reitverletzungen und Verletzungen beim Umgang mit Pferden bei erfahrenen Reitern |
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0177-5537 |
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PMID:9553480 |
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Equine Behaviour @ team @ |
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3735 |
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