Keil, N. M., Sambraus, H.H. (1998). “Intervenors” in agonistic interactions amongst domesticated goats. Z. Säugetierk., 63(5), 266–272.
Abstract: Social behaviour was observed in individually marked goats in two herds. The goats from one herd (n = 98) were horned, those of the other herd (n = 83) were polled. By recording agonistic interactions within the herds, a dominance index was determined for each animal. In both herds, intervention took place. Intervention is defined as one animal pushing in between two fighters, and thus ending the fight. More cases of intervention took place per individual animal amongst the horned goats than amongst the polled ones. Goats which intervened in fights on several occasions usually had a high dominance index. Members of the herd which were observed intervening only once had an average dominance index in both herds of almost 0.5. In some cases, goats very low in the rank order intervened a fight. Only rarely did the intervenors have a lower dominance index than the two fighters. In 103 cases, the direct dominance relationship between a fighting animal and the intervenor was known. In 95 cases (92.2%), the intervenor was dominant to the herd member in this fight and in just eight cases (7.8%), it was subordinate. It could not be determined what advantage the intervenor gained from its activity. It is possible that, at least in certain cases, a particularly relationship existed between the intervenor and one of the fighters.
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Connor, R. C., Mann, J., Tyack, P. L., & Whitehead, H. (1998). Social evolution in toothed whales. Trends. Ecol. Evol, 13(6), 228–232.
Abstract: 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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McLaren I.P.L. (1998). Animal Learning and Cognition: A neural network approach. Trends. Cognit. Sci., 2, 236.
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Vallortigara G. (1998). Minds of Their Own. Trends. Cognit. Sci., 2, 118.
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Lachmann M., & Bergstrom C.T. (1998). Signalling among Relatives II. Beyond the Tower of Babel. Theor. Pop. Biol., 54(2).
Abstract: 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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Clement, T. S., Weaver, J. E., Sherburne, L. M., & Zentall, T. R. (1998). Simultaneous discrimination learning in pigeons: value of S- affects the relative value of its associated S+. Q J Exp Psychol B, 51(4), 363–378.
Abstract: 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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Khalil, A. M., Murakami, N., & Kaseda, Y. (1998). Relationship between plasma testosterone concentrations and age, breeding season and harem size in Misaki feral horses. J Vet Med Sci, 60(5), 643–645.
Abstract: Jugular vein blood samples were collected from 23 young and sexual mature feral stallions to examine the relationship between plasma testosterone concentration and age, breeding season or harem size. Testosterone concentration increased with the age of the stallions until they formed their own harems, at about 4 to 6 years old. Seasonal variations in testosterone concentrations were observed, and found to be significantly higher (P<0.001) throughout the breeding season than non-breeding season, from 3 years of age. Testosterone levels were correlated with harem size for individual stallions. It can be inferred from these results that there is a relationship between plasma testosterone concentration and age, breeding season and harem size.
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Cox, G., & Ashford, T. (1998). Riddle Me This: The Craft and Concept of Animal Mind. Science Technology Human Values, 23(4), 425–438.
Abstract: This article examines the relations between methods used in both animal work and study and concepts of animal mind. By “animal work” the authors mean humans and animals working together, and by “animal study” they mean the discipline of ethology, especially the emerging area of cognitive ethology. Within these areas the wide range of conceptions of animal mind includes varying emphases on intelligence, forms of rationality and language, cognition, consciousness, and intentionality. The authors' central concern is to elucidate the vocabulary and the concepts which seem necessary to establishing successful working relationships with sheepdogs and gundogs. Their argument moves toward an emphasis on the appreciation of particular intentional states and recognizes that they invariably deploy elements of a moral vocabulary in achieving creative teamwork performances with dogs and other animals. The article concludes by consid enng the relevance of accounts of work with animals for associated considerations of intentionality.
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Brannon, E. M., & Terrace, H. S. (1998). Ordering of the numerosities 1 to 9 by monkeys. Science, 282(5389), 746–749.
Abstract: 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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Schnall, S., & Gattis, M. (1998). Transitive Inference by Visual Reasoning.
Abstract: Two experiments are reported that investigated the influence
of linear spatial organization on transitive inference
performance. Reward/no-reward relations between
overlapping pairs of elements were presented in a context of
linear spatial order or random spatial order. Participants in
the linear arrangement condition showed evidence for visual
reasoning: They systematically mapped spatial relations to
conceptual relation and used the spatial relations to make
inferences on a reasoning task in a new spatial context. We
suggest that linear ordering may be a “good figure”, by
constituting a parsimonious representation for the integration
of premises, as well as for the inferencing process. The late
emergence of transitive inference in children may be the
result of limited cognitive capacity, which --unless an
external spatial array is available --constrains the
construction of an internal spatial array.
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